Effects of nutrition and management during the stocker phase on quality grade
White Paper
Certified Angus Beef
Clint R. Krehbiel*, Phillip A. Lancaster*, Evin D. Sharman*, Gerald W. Horn*, D. L.
Step**, and Deb L. VanOverbeke*
*Department of Animal Sciences, Division of Agricultural Sciences and Natural Resources; and
**Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, Oklahoma
State University, Stillwater, 74078
INTRODUCTION
The 2011 National Beef Quality Audit Survey reported that “Eating Satisfaction”
(defined by packers as tenderness, flavor-marbling) is the second most important attribute in beef
consumption behind food safety (Igo et al., 2012). Retained ownership, alliances, and vertically
coordinated supply chains are becoming an increasingly larger percentage of cattle on feed,
resulting in an estimated 50% or greater of the cattle in the U.S. trading outside of the cash
market (Ritchie, 2002). As segments of the beef industry become more coordinated, it becomes
increasingly important to understand the effects that management and nutrition in each segment
has on all subsequent phases of production, final carcass value, and “Eating Satisfaction” of the
final products. Improving nutritional and management strategies for growing beef cattle to
enhance final carcass quality will not only benefit the beef industry as a whole, but will provide
producers with more incentive to produce high-quality beef to meet consumer demand. Because
consumer dollars ultimately drive the beef cattle industry, meeting consumer demand/desires will
continue to determine profitability in the future.
Studies of nutrition and management practices that influence marbling (intramuscular fat)
deposition have primarily focused on the feedlot phase of production (Owens and Gardner,
1
2000). However, pre-feedyard management strategies (health status, stocker/backgrounding,
nutrient supplementation, etc.) can influence marbling development (Anderson and Gleghorn,
2007). Therefore, changes in management practices during early phases of the production cycle
that increase intramuscular fat deposition and decrease fat deposition in other depots could
enhance the efficiency of beef production and enhance carcass quality. Due to the current price
of grains and harvested forages, cattle are entering the feedlot at heavier weights indicating that
post-weaning management programs are being used to decrease the number of days cattle spend
in the feedyard. Understanding how these post-weaning nutrition and management programs
impact carcass growth and development is becoming increasingly important.
Depending on biological type of cattle, calves are often grazed or placed on a growing
diet after weaning to achieve adequate frame size and carcass weight before entering the feedlot
for finishing. Across the Southern Great Plains and the Southeastern U.S., grazing systems are
commonly used for growing programs during the winter. Cool season forages, including wheat
pasture, are utilized to grow cattle to desirable weights for feedlot entry (Byers, 1982). In
addition, each year in the Southern Great Plains fall-weaned calves are wintered on dormant
native range. Cattle that are wintered on dormant native range are typically fed a protein
supplement to gain 0.25 to 0.50 kg/day through the winter months until spring forage growth
occurs. These calves then graze summer pasture in either intensive-early stocking or season-long
grazing programs prior to entering the finishing phase. In the Northern Great Plains, cattle are
usually either grown on crop residues, dormant grass pastures, or placed in confinement and
program fed for a moderate rate of gain on harvested and ensiled crops such as corn silage.
Albeit stocker programs are increasing due to costs of gain in the feedyard, some larger-framed
calves may go directly on to a high-concentrate diet immediately following weaning. High-
2
concentrate diets may be fed at restricted levels in the growing phase to provide a desired rate of
gain while allowing for lean tissue growth (Sip and Pritchard, 1991). Because of the variability
in growing programs among different regions of the country and in diets that may consist of
grazed or harvested forage and/or grain-based diets, performance and weight gain of cattle before
and after feedlot entry may be vastly different (McCurdy et al., 2010). In addition, development
of fat depots in relation to BW and maturity of the animal could be impacted to alter carcass
quality. Because economic value of carcasses is dependent primarily on carcass weight and
carcass quality, cattle producers have a strong interest in factors associated with maximizing
these two variables. This review will focus on stocker cattle nutrition and management strategies
that have the potential to impact marbling score and carcass quality.
MARBLING DEPOSITION DURING THE STOCKER PHASE
Adipose (fat) tissue development is of major importance to beef production because it
influences production efficiency, product quality and consumer acceptance, and, therefore,
product value (Smith et al., 1987). Growth of the intramuscular fat depot (i.e., marbling) is
especially desirable due to consumer preference for well-marbled beef, whereas growth of other
fat depots results in excess fat and production inefficiencies (Hausman et al., 2009). In addition,
the amount of fat deposited in the intramuscular depot is the basis for carcass price premiums
(marbling; USDA Quality Grade) and fat deposited in other depots can result in carcass
discounts (subcutaneous fat; USDA Yield Grade). Anderson and Gleghorn (2007) suggested
that marbling deposition is a lifetime event and that pre-feedlot nutrition has a significant impact
on marbling deposition. Peel (2003) estimated that 76% of the yearly calf crop enters a
backgrounding or stocker program prior to finishing; therefore, there is tremendous opportunity
to improve carcass quality attributes by influencing adipose tissue development during the
3
stocker/backgrounding phase of production. During the stocker/backgrounding phase of
production, significant muscle growth occurs and the primary structures of marbling deposits are
developed. Although increasing intramuscular fat deposition relative to other fat depots would
be beneficial, little is known about the association between muscle growth, metabolism and
marbling development.
Fat Cell Differentiation and Development
Understanding the molecular mechanisms responsible for fat cell development may
provide insight into how fat deposition can be influenced during the stocker phase of production,
whether from nutrition, management, or genetics. Growth of intramuscular fat appears to occur
due to adipocyte (fat cell) acquisition by differentiation of preadipocytes (adipogenesis;
Minoshima et al., 2001). Adipocytes represent between 1/3 and 2/3 of the cells in adipose tissue.
The remaining 1/3 to 2/3 consists of blood cells, endothelial cells, pericytes, preadipocytes, and
fibroblasts (Ailhaud et a1., 1992). Late in embryonic life the first preadipocytes appear.
However, expansion of white adipocytes does not occur until shortly after birth (Slavin, 1979;
Cook and Kozak, 1982). The expansion of white adipocytes that occurs shortly after birth
includes both an increase in the size (hypertrophy) and number (hyperplasia) of adipose cells.
Interestingly, even in adult animals, the potential to increase the number of adipose cells exists
(Gregoire et al., 1998). Lineage of adipose is derived from multipotent stem cells of mesodermal
origin. These multipotent stem cells can differentiate into muscle, cartilage, as well as fat
(Cornelius et al., 1994). Adipogenic cells, as well as osteogenic and chondrogenic cells, may
arise from sclerotomal cells (Gregoire et al., 1998). Adipoblasts formed from multipotent stem
cells undergo commitment to form preadipocytes. Preadipocytes are characterized as possessing
early genetic markers of adipocytes, but they have not at this point accumulated triacylglycerol
4
(lipid) stores (Ailhaud et al., 1992). The process of adipose differentiation corresponds to
phenotypic changes beginning with the adipoblast, progressing to the preadipocyte, becoming an
immature fat cell, and finally, terminally differentiating into the mature fat cell (Ailhaud et al.,
1992).
In order to induce the differentiation of preadipocytes to mature adipocytes, external
inducers are required. Inducers considered to be required for adipocyte differentiation to occur
include insulin-like growth factor-1 (IGF-1), glucocorticoid, cyclic adenosine monophosphate
(cAMP), and long chain fatty acids. Considerable numbers of IGF-1 receptors are found on
preadipocytes. In addition, insulin and growth hormone, driven by nutrition and management
(e.g., anabolic implants), are able to induce adipocyte differentiation via the IGF-l receptor.
Glucocorticoid is an adipogenic agent required for preadipocytes to undergo clonal expansion
and terminal differentiation (MacDougald and Lane, 1995). In addition, increased levels of
cAMP are required for preadipocyte cells to undergo differentiation into mature adipocytes
(Vassaux et al., 1992). It has also been shown that long chain fatty acids can induce
differentiation of preadipocytes. For example, palmitic acid (C16:0) can induce growth arrested
cells to undergo post-confluence mitosis (clonal expansion), to accumulate triacylglycerol, and to
express several adipocyte markers (Amri et al., 1995).
Intramuscular fat cells develop within the perimysium of muscle bundles in close
association with the skeletal muscle satellite cells responsible for postnatal muscle growth.
Therefore, skeletal muscle growth and metabolism might influence marbling development.
Intramuscular fat content is positively correlated (r = 0.46 to 0.49) with fiber area of oxidative
muscle fiber types (Melton et al., 1974; May et al., 1977) and number of capillaries per muscle
fiber (r = 0.63; Melton et al., 1975). In addition, Kim et al. (2009) reported that gene expression
5
of NADH dehydrogenase and cytochrome c oxidase, both involved in oxidative phosphorylation
within mitochondria, were greater in muscle from the loin, which had greater intramuscular fat
content, compared with muscle from the top round. Gene expression of NADH dehydrogenase
and cytochrome c oxidase explained 84 and 97% of the variation in intramuscular fat content of
loin muscle, respectively, in Korean cattle (Kim et al., 2009). These data suggest that muscle
metabolism influences marbling development.
Possible mechanisms by which muscle influences marbling development could include
increased angiogenesis (growth of blood vessels) within muscle providing greater blood flow to
sustain new adipocytes and changes in intercellular signaling mechanisms such as growth factors
that stimulate adipocyte differentiation. Angiogenesis is an important aspect of adipose tissue
development, and adipocyte differentiation may be regulated by factors that stimulate
angiogenesis (Hausman and Richardson, 2004). Under the microscope, it can be seen that
intramuscular adipocytes develop in close proximity to a capillary network (Harper and Pethick,
2004), and an important player in angiogenesis, the plasminogen activator-plasmin system, is
involved in the migration of endothelial cells and preadipocytes (Hausman and Richardson,
2004). Thus, enhancing vascular development of muscle tissue could stimulate recruitment of
preadipocytes to new locations within the muscle forming new intramuscular fat deposits.
As compared to other adipose tissues, intramuscular adipose tissue is more likely to be
influenced by the environment within the muscle tissue. Intramuscular adipose tissue has
smaller mature adipocytes (Smith and Crouse, 1984; Cianzio et al., 1985; May et al., 1994) and
preadipocytes from intramuscular adipose tissue have reduced capacity to differentiate (Grant et
al., 2008; Ortiz-Colon et al., 2009) compared to other adipose tissue depots. This may be due to
effects of the intramuscular environment or differences in the genetically determined growth
6
potential. Postnatal growth of bovine adipose tissue occurs by hypertrophy (cell size) through fat
synthesis, and hyperplasia (cell number) due to differentiation of preadipocytes (Gerrard and
Grant, 2003). As mentioned, several studies (Smith and Crouse, 1984; Cianzio et al., 1985;
Schoonmaker et al., 2004) have reported that intramuscular adipose tissue has a greater number
of smaller adipocytes compared to subcutaneous and perirenal adipose tissue. In addition,
perirenal adipose tissue has greater mean adipocyte diameter than subcutaneous adipose tissue
(Prior, 1983; Cianzio et al., 1985). These differences in hypertrophy may be related to rate and
substrate utilized for triacylglycerol synthesis. Smith and Crouse (1984) reported that
intramuscular adipose tissue had greater rates of fatty acid synthesis from glucose compared to
subcutaneous adipose tissue, whereas, subcutaneous adipose tissue had greater rates when
acetate or lactate were provided in vitro. However, rates of glycerol synthesis were greater for
subcutaneous adipose tissue irrespective of carbon source suggesting that subcutaneous adipose
tissue has greater rates of triacylglycerol synthesis and lipid storage than intramuscular adipose
tissue. Results of Rhoades et al. (2007) also indicated that rates of glycerol synthesis were
greater in subcutaneous than intramuscular adipose tissue. In addition, glucose incorporation
into lipids in intramuscular adipose tissue responded to insulin, whereas insulin had no effect in
subcutaneous adipose tissue (Rhoades et al., 2007). The response of intramuscular adipose tissue
was also modulated by diet, such that a corn-based high-glucose diet resulted in an insulin
response, whereas, a hay-based low-glucose diet did not. Differences in insulin response related
to diet may also exist between subcutaneous and internal fat depots.
Developmental differences between intramuscular and other fat depots have lead to an
interest in nutrition and management strategies to enhance marbling deposition while decreasing
fat deposition in other depots. Because intramuscular fat deposition is a lifetime event and
7
potentially associated with muscle growth and development, stocker programs that vary in
nutrient quantity and quality and cattle growth rates likely have a significant impact on marbling
deposition.
FACTORS THAT IMPACT MARBLING IN STOCKER CATTLE
Several factors have been shown to alter carcass quality in stocker cattle including animal
health, nutrition, management and genetics.
Animal Health
Bovine Respiratory Disease. Verification of health or preconditioning programs for
feeder calves before they begin the finishing phase of production is becoming more common in
the beef cattle industry. With the demand for higher quality products, the increase in valuebased marketing, and the increase in vertical coordination systems, both cow-calf producers and
feedlot operators have become more in-tune to health management practices that have the
potential to increase overall profitability. The health status of calves upon arrival to the feedyard
has been shown to impact the efficiency of cattle in the feedyard, and also to affect the quality
attributes of the cattle at slaughter. McNeill (1994, 1995, 1996, 1997, 1998) and Montgomery et
al. (1984) documented that morbid cattle during the finishing phase of production had carcasses
with a lower degree of marbling and subsequently lower USDA Quality Grades. Therefore,
although the medical costs attributable to the treatment of bovine respiratory disease (BRD) are
substantial (Martin et al., 1982; Perino, 1992), the economic impact of BRD on animal
performance, carcass merit, and meat quality are likely even more devastating.
Morbidity rates account for approximately eight percent of all production costs without
consideration of losses due to decreased performance (Griffen et al., 1995). McNeill et al.
8
(1996) reported that “healthy” steers had greater daily gains and 12% more USDA Choice
carcasses than cattle identified as “sick” at some point during the finishing period. Gardner et al.
(1999) showed that steers with lung lesions plus active lymph nodes had $73.78 less net return,
of which 21% was due to medicine costs and 79% due to lower carcass weight (8.4% less) and
lower quality grade (24.7% more USDA Standards). This negative impact on carcass traits 200 d
after receiving the cattle illustrates the importance of preventing BRD. Roeber et al. (2001)
documented that although cattle treated more than once in the feedyard had lower marbling score
and hot carcass weight (HCW) than those not treated, within a quality grade class, no differences
for tenderness or palatability traits existed in cattle stratified by number of hospital visits or
preconditioning treatment program.
Garcia et al. (2010) evaluated the effects of BRD on carcass composition and meat
quality traits in two separate herds at the U.S. Meat Animal Research Center, Clay Center, NE.
Cattle showing signs of BRD experienced a 11 lb decrease in HCW, and a 10 to 15% decrease in
12th-rib fat thickness resulting in a 5 to 7% decrease in USDA Yield Grade. These authors also
evaluated the effects of overall pathogenic disease on carcass traits. If an animal experienced
any disease event, 12th-rib fat thickness was decreased 12 to 14%, and USDA Yield Grade was
decreased by 0.2 units. Similarly, Schneider et al. (2009) reported a 2.5% decrease in HCW, a
slight decrease in LM area, a 7.0% decrease in 12th-rib fat thickness, and a 2.5% decrease in
marbling score in treated vs. non-treated cattle. Gardner et al. (1999) examined the effects of the
number of times treated on carcass characteristics. Hot carcass weight was decreased 4.1%,
12th-rib fat thickness was decreased 26.5%, and KPH and USDA Yield Grade were also
decreased in treated vs. non-treated calves. Similarly, HCW was decreased by 4.7%, 12th-rib fat
thickness by 43.4%, and KPH and USDA Yield Grade by 21.1 and 18.2%, respectively, when
9
cattle were treated more than once compared with cattle only treated once (Gardner et al., 1999).
When morbidity was defined by the presence of lung lesions at slaughter, Gardner et al. (1999)
observed morbid steers had HCW that were 94% of HCW of steers with no evidence of prior
disease. Additionally, when active bronchial lymph nodes were present, indicating an ongoing
disease process, HCW were less than HCW of animals with no lesions. In general, evidence of
prior morbidity was associated with decreased dressing percentage, internal fat, external fat,
smaller LM area, and lower marbling scores. Similar results were noticed when carcass
characteristics were examined based on BRD treatment records. Cattle that received more than
one treatment for BRD had an additional 5% decrease in HCW compared with those that were
treated only one time (Gardner et al., 1999).
Roeber et al. (2001) reported a 3% decline in HCW in steers treated more than one time
for BRD compared to those treated one time. However, in their report, no differences in HCW
were observed between cattle never treated and those treated one time, and no differences in
HCW across number of BRD treatments were reported by Waggoner et al. (2007). Although
fewer differences in carcass weights and no differences in LM area were reported by Roeber et
al. (2001), measures of carcass fatness were affected by BRD incidence. While internal fat was
not different among treatment groups, 12th-rib fat thickness, calculated yield grade, and
marbling score were all greatest for cattle never treated, intermediate for those treated once, and
lowest after multiple treatments. As a result of differences in marbling, the distribution of
USDA Quality Grades has been shown to be affected by BRD. Gardner et al. (1999) observed
that treated steers, or steers with lung lesions, had a greater percentage of USDA Standard
carcasses at the expense of Choice and Select compared with healthy animals. Similarly,
McNeill et al. (1996), in an evaluation of over 7,000 cattle, reported 39% of cattle never treated
10
for BRD graded USDA Choice or better, but only 27% that were treated graded USDA Choice
or better. Holland et al. (2010) noted a trend for a linear decrease in marbling score with
increasing number of treatments for BRD when cattle were fed to a targeted 12th-rib fat
thickness of 1.27 cm. There were no differences in proportions of USDA Yield Grades or
Quality Grades; however, meat color score and overall appearance of strip loin steaks decreased
as the number of times treated for BRD increased. There was no effect of number of BRD
treatments on Warner Bratzler Shear Force (WBSF), but there was a trend for an increased
amount of connective tissue determined by trained sensory panelists as the number of treatments
increased.
It is apparent that BRD has negative effects on carcass characteristics. Data show that fat
deposition by cattle is the most directly affected; however, decreased growth and anorexia also
occurs as evidenced by decreased HCW. It may be possible to achieve similar HCW, although
animals would need to be sorted by number of times treated for BRD and fed for additional days
(Holland et al., 2010). Other than in chronically infected cattle, this would indicate that BRD
constraints on growth are relieved with time. However, the trend for decreased marbling score
with increased number of treatments observed by Holland et al. (2010) suggests that quality of
carcasses may not fully recover even with increased days on feed.
Deworming. Internal parasites in cattle have been shown to decrease performance and
impair immune function (Wiggin and Gibbs, 1990; Smith et al., 2000; Reinhardt et al., 2006). In
feedlot cattle, infection of cattle by Ostertagia ostertagi decreased feed intake, average daily
gain (ADG), and efficiency of protein digestion (Fox et al., 1989), and infected cattle treated
with fenbendazole ate more feed than nontreated controls (Fox et al., 1989; Smith et al., 2000).
Reinhardt et al. (2006) reported that the percentage of USDA Prime or Choice carcasses tended
11
to be increased and USDA Standard carcasses decreased when feedlot heifers were treated with
fenbendazole and ivermectin pour-on compared to heifers treated with ivermectin pour-on alone.
Marbling score also tended to be greater for heifers treated with the combination of fenbendazole
and ivermectin pour-on. The increased degree of body fat was consistent with the noted increase
in dry matter intake (DMI). Feedlot deworming of steers not dewormed on pasture increased
carcass weight by 49 lb, while feedlot deworming of steers that were dewormed on pasture
increased carcass weight by 21 lb (Smith et al., 2000). The percentage of Choice carcasses was
lower and the percentage of Select carcasses was greater for steers not dewormed on pasture or
in the feedlot compared to treatments groups that were dewormed. Deworming during grazing
resulted in a net benefit of $33.75 per steer had steers been sold at the end of the grazing phase.
For the complete grazing-finishing system, feedlot deworming of previously non-dewormed
steers with fenbendazole produced a net benefit of $30.61 per steer on a carcass-adjusted basis,
while feedlot deworming of dewormed steers produced a net benefit of $11.07. Therefore, there
are clear performance and economic benefits to deworming grazing steers on pasture, and to
deworming yearling steers entering the feedlot from summer pasture. In general, management
practices that promote improved animal health will have a positive impact on marbling score and
carcass quality.
Nutrition
As previously mentioned, Smith and Crouse (1984) reported that intramuscular
adipocytes preferentially utilize glucose as the primary substrate for fatty acid synthesis; whereas
subcutaneous fat utilizes acetate. This led to studies conducted at the University of Illinois
where researchers showed that suckling calves provided a corn-based creep feed had increased
marbling scores at the end of finishing compared to calves provided a soyhull-based creep feed,
12
suggesting that increased glucose supply from corn supplementation improved marbling
deposition (Faulkner et al., 1994). Similarly, Myers et al. (1999b) and Shike et al. (2007)
reported that early weaned calves placed directly on a finishing diet had greater marbling scores
compared with calves that were normal weaned with and without creep feed. These data suggest
that an increase in starch intake early in an animal’s life may begin to initiate marbling
development and improve final carcass quality.
Numerous investigations have also sought to determine the effects of nutrition and
management throughout the production chain on deposition of marbling and subsequent carcass
quality (Berger and Faulkner, 2003). Increases in marbling have been shown by starting cattle
on high-concentrate rations at earlier ages (Myers et al., 1999a; 1999b; Wertz et al., 2001, 2002);
however, these cases dealt with calves that were early weaned and started on feed at very early
ages (70 to 100 days of age). Wertz et al. (2002) evaluated the effect of weaning calves and
growing them on forage compared to early-weaning calves and immediately placing them on a
high-concentrate diet. Early-weaned heifer calves were approximately 20% more efficient at any
ultrasound marbling score compared with older heifers that had grazed and were placed on feed
later in life. In addition, at any given 12th-rib fat thickness, early-weaned calves had higher
ultrasound marbling scores. In a similar study, Angus × Simmental heifer calves that were fed
high-energy diets at 208 days of age or earlier deposited more marbling relative to 12th-rib fat
than heifers of the same genetics that were finished as long yearlings (Wertz et al., 2001).
In normal-weaned calves (approximately 200 days of age), Faulkner et al. (1994) showed
that creep feed energy source could affect carcass quality even when weight gain was similar
during the creep phase. In their experiment, calves which had been fed a corn-based creep had
higher marbling scores than calves which had been creep fed soy hulls. In contrast, no difference
13
in marbling score was observed in normal-weaned calves creep-fed high corn, high fiber, or no
creep (Berger and Faulkner, 2003). Reasons for discrepancies are unclear, although Bruns
(2006) suggested that if calves can sustain their normal growth curve without additional
supplementation then creep feeding won’t increase quality grade. However, if the calves are
growing below their growth potential, due to inadequate nutrition, then creep feeding or early
weaning should help their ability to grade. Even though early weaned calves generally have
lower average daily gains in the finishing phase than yearlings, they are consuming excess
calories early in life above their requirement for normal growth. Therefore, marbling
(intramuscular fat) deposition might be greater compared with normal-weaned calves (Bruns,
2006).
Level of dietary starch during backgrounding. We conducted a meta-analysis to evaluate
the level of dietary starch in growing diets during the stocker/backgrounding phase. A dataset
with a total of 14 studies was compiled comparing growing diets fed to beef cattle in the drylot
that differed in grain content of the diet (i.e., starch content) for 56 to 145 d prior to finishing. To
be included in the dataset, feed intake of the different diets had to be adjusted to provide similar
NEg intake and achieve similar rates of gain during the growing phase. Treatments were
categorized as either low (LS), medium (MS), or high (HS) starch diets based on grain and NEg
content of the diet. Corn was the predominate cereal grain used except in the study by Sainz et al.
(1995), which used rolled wheat in the HS diet. Grain content of the diet was calculated from the
reported ingredient composition of the experimental diets, where corn or sorghum silage was
assumed to contain 50% grain. Seven studies had a comparison of HS versus MS, and 9 studies
had a comparison of HS versus LS. Only 2 studies had a comparison of MS versus LS; therefore
this comparison was not analyzed. The dataset was divided into two sub-datasets of either HS
14
versus MS or HS versus LS. Grain content, NEg concentration, and growing ADG for HS versus
MS, and HS versus LS sub-datasets are presented in Table 1. Each sub-dataset was analyzed
using a linear mixed model (Proc Mixed of SAS, SAS Instit., Cary, NC) that included diet as a
fixed effect and intercept as a random effect with the unstructured option used for the var-(co)var
matrix and trial as the subject. Least squares means were computed using the inverse of the
squared standard error for the dependent variable as a weighting factor (St-Pierre, 2001). Least
squares means were compared using Tukey’s W procedure and were considered different at P <
0.10.
Results of the HS versus MS comparison are presented in Table 2. Finishing performance
was similar between diet types with no differences for ADG, DMI, or gain:feed. In addition,
there were no differences in LM area, rib fat thickness, KPH, yield grade, or marbling score
between steers previously fed HS or MS diets during the growing phase. Of the individual
studies used in the meta-analysis, the results consistently show little to no difference in marbling
score with regard to grain content of the growing diet. In three trials, Loerch (1990) fed Angus
crossbred steers a corn silage-based growing diet ad libitum or high moisture corn-based diet at
restricted intake for 85 d prior to finishing on a common diet. In all three trials, growing diet had
no impact on final marbling score. Similarly, Sip and Pritchard (1991), Coleman et al. (1995)
and McCurdy et al. (2010) found that corn-grain based growing diets did not improve marbling
score compared with corn/sorghum silage-based growing diets. Gunter et al. (1996) and
Vasconcelos et al. (2009) reported that marbling scores were similar between steers fed 90%
concentrate or 50 to 60% concentrate growing diets prior to finishing on a common diet.
When comparing finishing performance of steers fed HS or LS diets during the growing
phase, there were no differences in final BW, DMI, or gain:feed; however, steers previously fed
15
HS diets had greater (P < 0.10) ADG (1.76 vs. 1.67 kg/d, respectively) during the finishing phase
(Table 3). Steers fed HS or LS diets during the growing phase had similar LM area, rib fat
thickness, KPH, yield grade, and marbling score. Wagner (1988) fed growing steers a corn
silage/alfalfa-grass hay diet ad libitum or high moisture corn diet limit-fed to provide similar ME
intake as the corn silage/alfalfa-grass hay diet. Following the finishing phase, marbling score
was similar between growing diets. Similarly, Sainz et al. (1995) and Hill et al. (1996) observed
that final marbling score was similar between steers fed an alfalfa hay/cottonseed hull-based
growing diet or limit fed a grain-based diet. Vasconcelos et al. (2009) reported that steers limit
fed a steam-flaked corn diet had no impact on final marbling score compared with steers fed a
wheat midd/cottonseed hull growing diet ad libitum. McCurdy et al. (2010) compared carcass
characteristics of steers limit fed a grain-based diet with steers that grazed winter wheat pasture
managed such that rate of gain during the growing phase was similar (1.18 vs. 1.15 kg/d,
respectively). After finishing on a common diet, marbling score was similar between steers that
grazed wheat pasture and those that were fed the grain-based growing diet. Collectively, metaanalysis of these studies indicate that dietary starch content of growing diets has little impact on
final marbling score.
Level of starch supplementation during grazing. Supplementation of starch to grazing
cattle during the stocker phase has received less attention due to limited ability to dramatically
change the starch content of the overall diet compared with growing diets fed in drylot.
However, a few studies have evaluated starch-based supplements to grazing stocker cattle on
final carcass quality. Horn et al. (1995) reported that high-starch corn-based supplements fed to
steers grazing winter wheat pasture did not improve marbling score compared with steers fed a
high-fiber soybean hull/wheat midd-based supplements. Similarly, Bumpus (2006) and Sharman
16
et al. (2012) observed that high-starch supplements did not improve marbling score of steers
grazing ryegrass and winter wheat pasture, respectively, compared with high-fiber supplements.
Sharman et al. (2009) fed either corn, soybean hulls, or distillers grains at 1% of BW to steers
grazing dormant winter native range. Similar to previous studies, these authors observed no
difference in final marbling score between the different supplement types, even though glucose
supply for steers grazing dormant native range would have been very low.
Interestingly, Lake et al. (1974) and Lomas et al. (2009) reported that supplementing
steers grazing cool-season pasture with 1.82 or 1.64 kg/d of grain increased marbling score
compared with no supplementation. However, in a second trial, Lake et al. (1974) observed no
improvement in quality grade when steers were supplemented up to 2.72 kg/d of corn. The
explanation for these differences could be that the starch-based supplement was not matched
with a fiber-based supplement such that the supplement provided additional energy for fat
deposition rather than a starch effect. Similarly, Bumpus (2006) observed that starch- and fiberbased supplements improved marbling score compared with non-supplemented steers, but rate of
gain during the stocker phase was not increased for supplemented steers compared with nonsupplemented steers. In contrast, Horn et al. (1995), Sharman et al. (2009), and Sharman et al.
(2012) observed that starch- or fiber-based supplements did not improve marbling score
compared with non-supplemented steers. Therefore, simply the additional energy does not
appear to explain the improved marbling scores.
Another explanation could be the BW of cattle during the stocker phase relative to mature
weight. Carter et al. (2002) evaluated the relationship between ultrasound intramuscular fat
percentage and BW when steers were grown on pasture and placed on feed at three different
weights (363, 408, or 454 kg initial finishing BW). These authors observed that regardless of
17
placement weight there was breakpoint BW of 378 kg at which intramuscular fat began to
increase. The breakpoint BW of 378 kg was calculated to be 64% of mature weight of the steers
or 66% of final feedlot BW. When applying this concept to previous studies, feedlot placement
BW of steers in Trial 1 of Lake et al. (1974), Bumpus (2006), and Lomas et al. (2009) were 73,
70, and 70% of final feedlot BW indicating that energy supplementation had increased energy
intake after the point at which intramuscular fat deposition increased. In contrast, feedlot
placement BW was only 66, 62, and 54% of final feedlot BW in the studies of Lake et al. (1974;
Trial 2), Horn et al. (1995), and Sharman et al. (2009) where final marbling score was not
influenced by energy supplementation during the stocker phase.
In conclusion, the starch content of growing diets or energy supplements fed to grazing
cattle does not appear to influence final marbling scores. In addition, energy supplementation of
lightweight stocker cattle may not improve final marbling score. However, energy
supplementation of heavyweight yearling stocker cattle could be beneficial for enhancing final
marbling score of cattle. Further research is necessary to validate the concept that providing an
energy supplement to heavyweight yearling stocker cattle could improve marbling scores.
Rate of gain during the stocker phase and placement weight. A second dataset consisting
of 29 trials was compiled to evaluate the relationships of rate of gain during the
stocker/backgrounding phase and initial BW at start of finishing with carcass characteristics. To
be included in the dataset, normal-weaned steers/heifers must have entered the stocker phase
shortly after weaning, and stocker treatments must have differed in rate of gain by > 0.10 kg/d
during the stocker phase. In this dataset, steers/heifers either grazed different forage types, were
fed with different levels of supplement while grazing pasture, or were fed high-roughage
growing diets in drylot to achieve different rates of gain during the stocker/backgrounding phase
18
prior to being fed a common finishing diet. In some trials, treatments were fed for similar days
on feed during the finishing phase, whereas in other trials treatments were fed to a common fat
endpoint with different days on feed. Mixed model regression analysis following random
coefficient methodology (St-Pierre, 2001) was used to evaluate the relationships of rate of gain
during the stocker/backgrounding phase and initial finishing BW with carcass characteristics and
rib fat-adjusted carcass characteristics. A general linear model (Proc GLM of SAS) that included
the covariate (i.e., stocker ADG or initial BW), trial, and trial x covariate interaction terms was
used to test the hypothesis that the slope between the covariate and carcass characteristics was
similar among trials. Regression analyses were conducted using a mixed model (Proc Mixed of
SAS) that included the covariate(s) as fixed effects, and intercept and covariate(s), when slopes
differed among trials, as random effects with the unstructured option used for the var-(co)var
matrix and trial as the subject. Regression coefficients were computed using the inverse of the
squared standard error for the dependent variable as a weighting factor (St-Pierre, 2001), and
were considered different from zero at P < 0.10. Quadratic regression coefficients were tested
and were not significant. Summary statistics for stocker performance and carcass characteristics
of the 29 trials are presented in Table 4.
Stocker phase ADG and initial finishing BW were positively related with HCW, LM
area, and KPH, but not rib fat thickness or yield grade (Table 5). Hot carcass weight was
positively related to LM area, rib fat thickness, and yield grade, but not KPH. These results
indicate that as cattle grew faster during the stocker phase and were heavier entering the feedyard
they produced heavier carcasses with larger longissimus muscle area, but had no influence on
carcass fat composition as evidenced by the lack of relationship with fat thickness and yield
grade.
19
Marbling score was not related to stocker phase ADG (Figure 1) or initial finishing BW
(Figure 2), but was positively related to HCW (Figure 3) suggesting that growth during the
stocker phase has little influence on marbling score and it is the weight of the animal at slaughter
that has the largest influence. Additionally, marbling score was positively related to rib fat
thickness [y = 291.82 ± 29.2048 + 92.5465 ± 22.2935 * rib fat thickness (cm)].
Given the relationship between marbling score and rib fat thickness and to evaluate
relationships with rib fat-adjusted carcass characteristics, rib fat thickness was included in the
regression of stocker phase ADG, initial finishing BW, and HCW with marbling score. When
adjusted for rib fat thickness, marbling score was positively related with stocker phase ADG,
initial finishing BW, and HCW suggesting that all three factors may play a role in influencing
marbling score when cattle are fed to a similar rib fat thickness. To determine the relative
importance of stocker phase ADG, initial finishing BW, and HCW with rib fat-adjusted marbling
score, these traits were included in the regression model to predict rib fat-adjusted marbling
score. When stocker ADG, initial finishing BW, and HCW were included in the model along
with rib fat thickness, HCW continued to be positively related to marbling score, but stocker
phase ADG and initial finishing BW were no longer related to marbling score (Figures 1, 2, and
3, respectively). Thus, it appears that increasing HCW will increase rib-fat adjusted marbling
score regardless of previous management. Our regression analysis indicates that greater stocker
phase ADG (Figure 4) or initial finishing BW (Figure 5) can increase HCW, which can be
accomplished through the use of higher quality forage, energy supplements, or longer grazing
periods. However, to increase rib fat-adjusted HCW, regression analysis indicates that lower
rates of gain (Figure 4) and longer grazing periods to achieve greater initial finishing BW (Figure
5) are needed.
20
These results may explain the lack of differences in marbling score in cattle from
different stocker and backgrounding studies (Coleman et al., 1995; Sainz et al., 1995; Hersom et
al., 2004; McCurdy et al., 2010), because even though cattle in these studies underwent widely
different growing programs the end result was similar HCW when fed to similar rib fat thickness.
Our results are also contrary to the idea that cattle should be grown at moderate to high rates of
gain and finished at young ages to achieve high quality grades. In agreement with our results,
Klopfenstein et al. (2000) reported that long-yearling production systems resulted in greater
initial finishing BW and HCW, and increased the percentage of cattle grading choice when
adjusted to similar rib fat thickness compared with calf-fed production systems. Similarly, Gill et
al. (1993) and Sharman et al. (2012) observed that steers wintered on dormant native range
followed by season-long grazing of native pasture prior to finishing increased initial finishing
BW and tended to increase marbling scores but lower rib fat thickness compared with steers
grazing winter wheat pasture prior to finishing.
In conclusion, marbling score and rib fat thickness-adjusted marbling score can be
manipulated using nutrition and management during the stocker phase. Marbling scores can be
improved by ‘making cattle bigger’ through increasing rate of gain during the stocker phase,
initial finishing BW, and HCW. However, this will also increase rib fat thickness and yield
grade resulting in little improvement in marbling to rib fat ratio. In contrast, rib fat-adjusted
marbling score (i.e., improved ratio of marbling to rib fat) can be improved by using low to
moderate rates of gain for longer grazing periods during the stocker phase to increase initial
finishing BW and rib fat-adjusted HCW.
Management
21
Growth Promoting Implants. Anabolic implants increase weight gains of beef cattle by
10 to 20% and are one of the most profitable management tools available to beef producers.
However, use of anabolic implants has been shown to have a negative impact on quality grade.
Duckett et al. (1997) reported that estrogenic implants administered to steers during finishing
decreased marbling score from 26 to 44 points; however, androgen alone had less effect,
decreasing marbling score 22 points and being statistically similar to controls. Morgan (1997)
reported that implants containing estrogen alone reduced marbling score 12 to 47 points,
androgen alone reduced marbling score 0 to 9 points, and combination implants reduced
marbling score 12 to 29 points in feedlot steers and heifers. In a meta-analysis of published
studies, McPhee et al. (2006) reported that estrogenic or combination implants reduced
intramuscular fat percent by 0.32 percentage units. Reinhardt (2010) reported that a metaanalysis of feedlot implant trials showed a reduction in marbling score of 49 points (548 vs. 499)
when using a very aggressive implant strategy of multiple strong combination implants.
Reinhardt (2010) also reported that as the implant program became more aggressive the decrease
in marbling score compared to non-implanted cattle became greater.
The reason for decreased marbling scores of implanted cattle could be attributed to a shift
in energy use for muscle growth rather than fat deposition or changes in the intramuscular
environment directing progenitor cells toward myogenesis rather than adipogenesis. Anabolic
implants alter body composition by decreasing fat composition and increasing lean. The decrease
in marbling score could be due to reduction in total fat deposition, but many studies (Simms et
al., 1988; Mader et al., 1994; Platter et al., 2003; Scheffler et al., 2003) have reported reduced
marbling scores even though cattle are fed to similar rib fat endpoints. Thus, the impact of
implants on marbling score appears to be due to a specific effect on intramuscular fat. In a
22
review, Chung and Johnson (2007) described a plausible mechanism whereby anabolic implants
could be stimulating progenitor cells within skeletal muscle to follow a myogenic lineage rather
than an adipogenic lineage. Thus, intramuscular fat development is influenced to a greater degree
than other fat depots.
There is concern that implanting cattle earlier in the production cycle (suckling or stocker
phase) has further negative impacts on quality grades. Platter et al. (2003) reported that
backgrounding implant tended (P =0.09) to decrease marbling score by 25 points. These authors
also reported that steers receiving 4 or 5 implants during their lifetime had significantly reduced
marbling scores (38 points) compared to steers only implanted twice in the feedlot. McMurphy et
al. (unpublished data) observed that fall-born steers implanted with Component TE-G after
weaning tended (P = 0.09) to have marbling scores 32 points lower than those not implanted
during the stocker phase. In contrast, Sharman et al. (2011) observed that fall-weaned steers
implanted with Component TE-G during the stocker phase had similar marbling scores compared
to steers not implanted during the stocker phase. The different responses observed in these
studies may be due to forage quality which would change energy available for fat deposition. In
the study by McMurphy and others, steers grazed summer native range, whereas steers grazed
winter wheat pasture in the study by Sharman et al. (2011). However, Paisley et al. (1999)
reported that steers implanted with Synovex-C, Synovex-S, or Revalor-G while grazing lowquality dormant winter native range had similar marbling scores compared with non-implanted
steers suggesting that forage quality does not influence the effect of stocker phase implants on
quality grades. Several studies (McCann et al., 1991; Brandt et al., 1995; Fankhauser et al.,
1997) have reported no effect of implants during the stocker phase on carcass quality grades. In
addition, Mader et al. (1985) and Simms et al. (1988) reported that steers implanted during the
23
growing phase while fed a corn silage-based diet in drylot had similar marbling scores compared
to steers implanted only during the finishing phase. Mader et al. (1994) observed that implanting
steers with Synovex-C during the suckling phase and Synovex-S during the stocker and finishing
phase did not negatively impact marbling score compared with steers only implanted during the
stocker and finishing phases.
Few studies have evaluated the effect of type of implant in stocker cattle on carcass
characteristics. Kuhl et al. (1997) evaluated the use of Ralgro, Revalor-G and Synovex-S for
grazing steers and reported no differences in carcass quality traits or yield grade among implants.
Frankhauser et al. (1997) evaluated Ralgro and Synovex-S in steers grazing native pastures under
intensive early stocking management prior to finishing. Type of grazing implant did not
influence marbling score or yield grade. Paisley et al. (1999) administered Synovex-C, SynovexS, or Revalor-G to steers grazing dormant winter native range prior to being implanted with
Ralgro while grazing summer pasture until mid-July. Following the subsequent finishing phase,
steers implanted with Synovex-C tended (P = 0.06) to have greater marbling scores than steers
implanted with Synovex-S or Revalor-G. Possibly the lower potency of Synovex-C did not
negatively affect intramuscular fat development; however, the non-implanted steers had
marbling scores intermediate to Synovex-C and Synovex-S/Revalor-G steers making it difficult
to discern the cause of the greater marbling score of Synovex-C steers.
Interestingly, Scheffler et al. (2003) and Simms et al. (1988) observed that the terminal
implant administered late in the finishing phase had the greatest negative impact on marbling
score. Scheffler et al. (2003) implanted long-fed Holstein steers 1 time on d 224, 2 times on d
112 and 224, 3 times on d 0, 112, and 224, or non-implanted control during a 291-d finishing
period. These authors reported that the single implant on d 224 decreased marbling score by 52
24
points compared to non-implanted controls, whereas implanting steers 2 or 3 times throughout
the finishing period only reduced marbling score by 31 and 34 points, respectively. Simms et al.
(1988) evaluated different combinations of four implant timings during the suckling, growing,
and finishing (early and late) phases compared with non-implanted steers. These authors reported
that any combination of implanting steers during the production cycle that included the latefinishing implant at 75 d prior to harvest decreased quality grade compared to non-implanted
controls. However, a combination of implants that eliminated the late-finishing implant did not
significantly decrease quality grade compared to non-implanted steers even though this
combination of implants included suckling, growing, and early-finishing implants. Therefore, it
appears that administration of implants closer to the end of the finishing phase have a greater
negative impact on quality grades, whereas administration of implants early in the production
cycle have little influence on quality grades if cattle are to be implanted during the finishing
phase.
Genetics
Bertrand et al. (2001) reported heritability estimates for several carcass traits adjusted to
an age constant or time-on-feed constant basis. The average heritability estimates for all traits
were in the moderate-to-high range, although there was a higher frequency of low (≤ 0.12)
estimates observed for Warner-Bratzler shear force and tenderness score. Large genetic
differences across breeds and small genetic differences within the breeds have been reported for
shear force and taste panel tenderness scores from reciprocal backcross and single-cross steers of
several breeds (Van Vleck et al., 1992). Van Vleck et al. (1992) also reported that large acrossbreed and within-breed genetic variation existed for marbling score. Adequate within-breed
genetic variation for shear force might warrant its inclusion in within-breed genetic evaluation
25
programs for breeds of cattle (Bertrand et al., 2001). In the review by Bertrand et al. (2001),
heritability estimates for carcass weight, ribeye area, shear force, marbling score, and calpastatin
activity averaged across studies evaluating carcasses at a fat constant endpoint were also shown
to be moderate to high. The authors concluded that on average, heritability estimates shown in
the literature indicate that carcass traits will respond well to selection, and that it may be possible
to select for increased growth within a breed without negatively impacting marbling score or
percentage retail product.
Quantitative trait loci (QTLs) are stretches of DNA that are closely linked to the genes
that underlie any given trait, such as characteristics of carcass quality and yield. Quantitative trait
loci can be molecularly identified to help “map” regions of the bovine genome that contain genes
involved in specifying a given quantitative trait. Bertrand et al. (2001) suggested that the QTL
that are identified through searches of the bovine gene map are likely to be most beneficial for
those traits that are difficult and/or expensive to measure, such as disease resistance and
immunocompetence, carcass quality and palatability attributes, fertility and reproductive
efficiency, maintenance requirements (i.e., energetic efficiency), carcass quantity and yield, milk
production and maternal ability, and growth performance (ranked from greatest benefit to least
benefit). Because hard-to-measure traits such as immunocompetence have a significant effect on
carcass quality, DNA-based tools for carcass trait selection will become increasingly useful.
CONCLUSIONS
No one factor solely contributes to carcass quality, but numerous factors interact to have
an effect. Calf health, nutrition, and management (e.g., implant strategy) prior to and during
feedlot finishing can have an impact on carcass quality. It is important to maintain the genetic
potential of calves to express growth performance and carcass quality through health
26
management programs and implant strategies during the stocker phase. Adequate caloric intake
at critical times to support both muscle and marbling development appears to improve the
percentage of cattle that will grade USDA Choice. Marbling scores can be improved by ‘making
cattle bigger’ through increasing rate of gain during the stocker phase, initial finishing BW, and
HCW. However, this will also increase rib fat thickness and yield grade resulting in little
improvement in marbling to rib fat ratio. In contrast, rib fat-adjusted marbling score (i.e.,
improved ratio of marbling to rib fat) can be improved by using low to moderate rates of gain for
longer grazing periods during the stocker phase to increase initial finishing BW and rib fatadjusted HCW. Finally, the potential exists for DNA-assisted selection to maintain or increase
muscle growth (ribeye area), while at the same time improving carcass quality (marbling score).
27
LITERATURE CITED
Aahaud, G., P. Grimaldi, and R Negrel. 1992. Cellular and molecular aspects of adipose tissue
development. Annu. Rev. Nutr. 12:207-233.
Amri, E. Z., F. Bonini, G. Ailhaud, N. A. Abumrad, and P. A. Grimaldi. 1995. Cloning of a
protein that mediates transcriptional effects of fatty acids in preadipocytes. Homology to
peroxisome proliferator-activated receptors. J. Biol. Chem. 270:2367-2371.
Anderson, P. and J. Gleghorn. 2007. Non-genetic factors that affect quality grade of fed cattle.
Pages 31-43 in Proc. Beef Improvement Federation 39th Annual Research Symposium
and Annual Meeting, Fort Collins, CO.
Berger, L. L. and D. B. Faulkner. 2003. Lifetime nutritional effects on feedlot performance and
carcass merit. Pages 63-78 in Plains Nutrition Council Spring Conference Proceedings.
Publication No. AREC 03-13. Texas A&M Research and Extension Center, Amarillo.
Bertrand, J. K., R. D. Green, W. O. Herring, and D. W. Moser. 2001. Genetic evaluation for
beef carcass traits. J. Anim. Sci. 79(E. Suppl.):E190–E200.
Brandt, R. T., Jr., C. E. Owenby, and C. T. Milton. 1995. Effects of grazing system and use of a
pasture-phase implant on grazing and finishing performance of steers. Kans. State
Cattlemen’s Day Rep. Prog. SRP-727:15-18.
Bruns, K. 2006. New insights in the development of marbling in beef cattle. Accessed at:
http://www.sdstate.edu/ars/species/beef/publications/index.cfm.
Bruns, K. W., R. H. Pritchard, and D. L. Boggs. 2004. The relationships among body weight,
body composition, and intramuscular fat content in steers. J. Anim. Sci. 82:1315-1322.
28
Bumpus, E. K. 2006. Influence of acetogenic versus propiogenic supplements on adipose tissue
accretion in stocker steers grazing ryegrass pasture. M.S. Thesis, Texas A&M Univ.,
College Station.
Byers, F. M. 1982. Nutritional factors affecting growth of muscle and adipose tissue in
ruminants. Fed. Proc. 41:2562-2565.
Carter, J. N., P. A. Ludden, M. S. Kerley, M. Ellersieck, W. O. Herring, and E. Berg. 2002.
Intramuscular fat deposition in steers is accelerated at a set body weight. Prof. Anim.
Sci. 18:135-140.
Chung, K. Y., and B. J. Johnson. 2007. Cellular aspects of intramuscular adipogenesis:
Competition for cells between muscle and marbling. Pages 9-25 in Plains Nutrition
Council Spring Conference Proceedings. Publication No. AREC 07-20. Texas A&M
Research and Extension Center, Amarillo.
Cianzio, D. S., D. G. Topel, G. B. Whitehurst, D. C. Beitz, and H. L. Self. 1985. Adipose tissue
growth and cellularity: Changes in bovine adipocyte size and number. J. Anim. Sci. 60:
970-976.
Coleman, S. W., R. H. Gallavan, C. B. Williams, W. A. Phillips, J. D. Volesky, S. Rodriguez,
and G. L. Bennett. 1995. Silage or limit-fed grain growing diets for steers: I. Growth
and carcass quality. J. Anim. Sci. 73:2609-2620.
Cook, J. R. and L. P. Kozak. 1982. Glycerol-3-phosphate dehydrogenase gene expression during
mouse adipocyte development in vivo. Dev. Biol. 92:440-448.
Cornelius, P., O. A. MacDougald, and M. D. Lane. 1994. Regulation of adipocyte development.
Annu. Rev. Nutr. 14:99-129.
29
Duckett, S. K., F. N. Owens, and J. G. Andrae. 1997. Effects of implants on performance and
carcass traits of feedlot steers and heifers. Proc. Impact of Implants on Performance and
Carcass Value of Beef Cattle, Okla. Exp. Stn., Stillwater. P-957:63–82.
Faulkner, D. B., D. F. Hummel, D. D. Buskirk, L. L. Berger, D. F. Parrett, and G. F. Cmarik.
1994. Performance and nutrient metabolism by nursing calves supplemented with limited
or unlimited corn or soyhulls. J. Anim. Sci. 72:470-477.
Fox, M. T., D. Gerrelli, S. R. Pitt, D. E. Jacobs, E. M. Gill, and D. L. Gale. 1989a. Ostertagia
ostertagi infection in the calf: Effects of a trickle challenge on appetite, digestibility, rate
of passage of digesta and live BW gain. Res. Vet. Sci. 47:294–298.
Frankhouser, T. R., G. L. Kuhl, J. S. Drouillard, D. D. Simms, G. L. Stokka, and D. A. Blasi.
1997. Influence of implanting grazing steers with Ralgro or Synovex-S followed by
Synovex Plus or a Ralgro/Synovex Plus reimplant program in the feedlot on
pasture/finishing performance and carcass merit. Kans. State Cattlemen’s Day Rep. Prog.
783:39-43.
Garcia, M. D., R. M. Thallman, T. L. Wheeler, S. D. Shackelford, and E. Casas. 2010. Effect of
bovine respiratory disease and overall pathogenic disease incidence on carcass traits. J.
Anim Sci. 88:491-496.
Gardner, B. A., H. G. Dolezal, L. K. Bryant, F. N. Owens, and R. A. Smith. 1999. Health of
finishing steers: Effects on performance, carcass traits, and meat tenderness. J. Anim. Sci.
77:3168-3175.
Gerrard, D. E., and A. L. Grant. 2003. Principles of animal growth and development.
Kendall/Hunt Publishing Co., Dubuque, IA.
30
Gill, D. R., F. N. Owens, M. C. King, and H. G. Dolezal. 1993. Body composition of feedlot
steers differing in age and background. Oklahoma Agricultural Experiment Station
Anim. Sci. Res. Rep. P-933:185-190.
Grant, A. C., G. Ortiz-Colon, M. E. Doumit, R. J. Tempelman, and D. D. Buskirk. 2008.
Differentiation of bovine intramuscular and subcutaneous stromal-vascular cells exposed
to dexamethasone and troglitazone. J. Anim. Sci. 86: 2531-2538.
Gregoire, F. M., C. M. Smas, and H. S. SuI. 1998. Understanding adipocyte differentiation.
Physio!. Rev. 78:783-809.
Griffin, D., L. Perino, and T. Whittum. 1995. Feedlot respiratory disease: Cost, value of
preventives and intervention. Proceedings, Annual Convention – Am. Assoc. of Bovine
Prac., vol. 27, San Antonio, TX. Am. Assoc. Bovine Prac., Rome, GA.
Gunter, S. A., M. L. Galyean, and K. J. Malcom-Callis. 1996. Factors influencing the
performance of feedlot steers limit-fed high-concentrate diets. Prof. Anim. Sci. 12:167175.
Harper, G. S., and D. W. Pethick. 2004. How might marbling begin? Aust. J. Exp. Agric. 44:653662.
Hausman, G. J., M. V. Dodson, K. Ajuwon, M. Azain, K. M. Barnes, L. L. Guan, Z. Jiang, S. P.
Poulos, R. D. Sainz, S. Smith, M. Spurlock, J. Novakofski, M. E. Fernyhough, and W. G.
Bergen. 2009. The biology and regulation of preadipocytes and adipocytes in meat
animals. J. Anim. Sci. 87:1218-1246.
Hausman, G. J., and R. L. Richardson. 2004. Adipose tissue angiogenesis. J. Anim. Sci. 82:925934.
31
Hersom, M. J., G. W. Horn, C. R. Krehbiel, and W. A. Phillips. 2004. Effect of live weight gain
of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body
composition of beef steers. J. Anim. Sci. 82:262-272.
Hill, W. J., D. S. Secrist, F. N. Owens, and D. R. Gill. 1996. Effects of limit feeding on fedlot
performance and carcass characteristics. Oklahoma Agricultural Experiment Station
Anim. Sci. Res. Rep. P-951:137-143.
Holland, B. P., L. O. Burciaga-Robles, D. L. VanOverbeke, J. N. Shook, D. L. Step, C. J.
Richards, and C. R. Krehbiel. 2010. Effect of bovine respiratory disease during
preconditioning on subsequent feedlot performance, carcass characteristics, and beef
attributes. J. Anim Sci. 88:2486-2499.
Horn, G. W., M. D. Cravey, F. T. McCollum, C. A. Strasia, E. G. Krenzer, Jr., and P. L.
Claypool. 1995. Influence of high-starch vs high-fiber energy supplements on
performance of stocker cattle grazing wheat pasture and subsequent feedlot performance.
J. Anim. Sci. 73:45-54.
Igo, J.L., D.L. VanOverbeke, G.G. Mafi, D.L. Pendell, D.S. Hale, J.W. Savell, D.R. Woerner,
J.D. Tatum, and K.E. Belk. 2012. 2011 National Beef Quality Audit Phase I: Face-toFace Interviews. Submitted to the National Cattlemen’s Beef Association, Centennial,
CO.
Kim, N. K., Y. M. Cho, Y. S. Jung, G. S. Kim, K. N. Heo, S. H. Lee, D. Lim, S. Cho, E. W.
Park, and D. Yoon. 2009. Gene expression profiling of metabolism-related genes
between top round and loin muscle of Korean cattle (Hanwoo). J. Agric. Food Chem.
57:10898-10903.
32
Klopfenstein, T., R. Cooper, D. J. Jordon, D. Shain, T. Milton, C. Calkins, and C. Rossi. 1999.
Effects of backgrounding and growing programs on beef carcass quality and yield.
Accessed at: http://www.asas.org/JAS/symposia/proceedings/0942.pdf. J. Anim. Sci.
79(E-Suppl.).
Kuhl, G. L. 1997. Stocker cattle responses to implants. Symposium: Impact of implants on
performance and carcass value of beef cattle. Oklahoma Agric. Exp. Sta. Stillwater. P957:51–62.
Lake, R. P., R. L. Hildebrand, D. C. Clanton, and L. E. Jones. 1974. Limited energy
supplementation of yearling steers grazing irrigated pasture and subsequent feedlot
performance. J. Anim. Sci. 39:827-833.
Loerch, S. C. 1990. Effects of feeding growing cattle high-concentrate diets at a restricted
intake on feedlot performance. J. Anim. Sci. 68:3086-3095.
Lomas, L. W., J. L. Moyer, and G. A. Milliken. 2009. Effect of energy supplementation of
stocker cattle grazing smooth bromegrass pastures on grazing and subsequent finishing
performance and carcass traits. Prof. Anim. Sci. 25:65-73.
MacDougald, O. A. and M. D. Lane. 1995. Transcriptional regulation of gene expression during
adipocyte differentiation. Annu. Rev. Biochem. 64:34.5-373.
Mader, T. L., D. C. Clanton, J. K. Ward, D. E. Pankaskie, and G. H. Deutscher. 1985. Effect of preand postweaning zeranol implant on steer calf performance. J. Anim. Sci. 61:546–551.
Mader, T. L., J. M. Dahlquist, M. H. Sindt, R. A. Stock, and T. J. Klopfenstein. 1994. Effect of
sequential implanting with Synovex on steer and heifer performance. J. Anim. Sci.
72:1095–1100.
33
Martin, S. W., A. H. Meek, D. G. Davis, J. A. Johnson, and R. A. Curtis. 1982. Factors
associated with mortality and treatment costs in feedlot calves: The Bruce County beef
project, years 1978, 1979, 1980. Can. J. Comp. Med. 46:341–349.
May, M. L., M. E. Dikeman, and R. Schalles. 1977. Longissimus muscle histological
characteristics of Simmental x Angus, Hereford x Angus and Limousin x Angus
crossbred steers as related to carcass composition and meat palatability traits. J. Anim.
Sci. 44:571-580.
May, S. G., J. W. Savell, D. K. Lunt, J. J. Wilson, J. C. Laurenz, and S. B. Smith. 1994.
Evidence for preadipocyte proliferation during culture of subcutaneous and intramuscular
adipose tissues from Angus and Wagyu crossbred steers. J. Anim. Sci. 72: 3110-3117.
McCann, M. A., R. S. Donaldson, H. E. Amos, and C. S. Hoveland. 1991. Ruminal escape
protein supplementation and zeranol implantation effects on performance of steers
grazing winter annuals. J. Anim. Sci. 69:3112-3117.
McCurdy, M. P., G. W. Horn, J. J. Wagner, P. A. Lancaster, and C. R. Krehbiel. 2010. Effects
of winter growing programs on subsequent feedlot performance, carcass characteristics,
body composition, and energy requirements of beef steers. J. Anim. Sci. 88:1564-1576.
McCurdy, M. P. 2006. Effect of winter growing program on subsequent feedlot performance,
body composition, carcass merit, organ mass and oxygen consumption in beef steers.
Ph.D. Dissertation. Oklahoma State University, Stillwater.
McNeill, J. W. 1994. 1993-94 Texas A & M Ranch to Rail North/South Summary Report.
Texas Agricultural Extension Service, Texas A & M University. College Station, TX.
McNeill, J. W. 1995. 1994-95 Texas A & M Ranch to Rail North/South Summary Report.
Texas Agricultural Extension Service, Texas A & M University. College Station, TX.
34
McNeill, J. W. 1996. 1995-96 Texas A & M Ranch to Rail North/South Summary Report.
Texas Agricultural Extension Service, Texas A & M University. College Station, TX.
McNeill, J. W., J. C. Paschal, M. S. McNeill, and W. W. Morgan. 1996. Effect of morbidity on
performance and profitability of feedlot steers. J. Anim. Sci. 74(Suppl. 1):135.
McNeill, J. W. 1997. 1996-97 Texas A & M Ranch to Rail North/South Summary Report.
Texas Agricultural Extension Service, Texas A & M University. College Station, TX.
McNeill, J. W. 1998. 1997-98 Texas A & M Ranch to Rail North/South Summary Report.
Texas Agricultural Extension Service, Texas A & M University. College Station, TX.
McPhee, M. J., J. W. Oltjen, T. R. Famula and R. D. Sainz. 2006. Meta-analysis of factors
affecting carcass characteristics of feedlot steers. J. Anim. Sci. 84:3143-3154.
Melton, C., M. Dikeman, H. J. Tuma, and R. R. Schalles. 1974. Histological relationships of
muscle biopsies to bovine meat quality and carcass composition. J. Anim. Sci. 38:24-31.
Melton, C. C., M. E. Dikeman, H. J. Tuma, and D. H. Kropf. 1975. Histochemical relationships
of muscle biopsies with bovine muscle quality and composition. J. Anim. Sci. 40:451456.
Minoshima, Y, Y Taniguchi, K. Tanaka, T. Yamada, and Y. Sasaki. 2001. Molecular cloning,
expression analysis, promoter characterization, and chromosomal localization of the
bovine PREFI gene. Animal Genetics. 32:333-339.
Montgomery, T. H., R. Adams, M. A. Cole, D. P. Hutcheson, and J. B. McLaren. 1984.
Influence of feeder calf management and bovine respiratory disease on carcass traits of
beef steers. Proceedings: Western Section, J. Anim. Sci. 35:319-327.
35
Morgan, J. B. 1997. Implant program effects on USDA beef carcass quality grade traits and meat
tenderness. Pages 147–154 in Proc. OSU Symp.: Impact of Implants on Performance and
Carcass Value of Beef Cattle, Oklahoma Agric. Exp. Stn., Stillwater, OK.
Myers, S. E., D. B, Faulkner, F. A. Ireland, L. L. Berger, and D. F. Parrett. 1999a. Production
systems comparing early weaning to normal weaning with or without creep feeding for
beef steers. J. Anim. Sci. 77:300-310.
Myers, S. E., D. B. Faulkner, F. A. Ireland, D. F. Parrett, and F. K. McKeith. 1999b.
Performance and carcass traits of early-weaned steers receiving either a pasture growing
period or a finishing diet at weaning. J. Anim. Sci. 77:311-322.
Myers, S. E., D. B. Faulkner, F. A. Ireland, and D. F. Parrett. 1999c. Comparison of three
weaning ages on cow-calf performance and steer carcass traits. J. Anim. Sci. 77:323-329.
Ortiz-Colon, G., A. C. Grant, M. E. Doumit, and D. D. Buskirk. 2009. Bovine intramuscular,
subcutaneous, and perirenal stromal-vascular cells express similar glucocorticoid receptor
isoforms, but exhibit different adipogenic capacity. J. Anim. Sci. 87:1913-1920.
Owens, F. N. and B. A. Gardner. 2000. A review of the impact of feedlot management and
nutrition on carcass measurements of feedlot cattle. J. Anim. Sci. 77:1-18.
Paisley, S. I., G. W. Horn, C. J. Ackerman, B. A. Gardner, and D. S. Secrist. 1999. Effects of
implants on daily gains of steers wintered on dormant native tallgrass prairie, subsequent
performance, and carcass characteristics. J. Anim. Sci. 77:291-299.
Peel, D. S. 2003. Beef cattle growing and backgrounding programs. Vet. Clin. North Am. Food
Anim. Prac. 19:365-385.
Perino, L. J. 1992. Overview of the bovine respiratory disease complex. Compend. Cont. Educ.
Pract. Vet. 14(Suppl.):3.
36
Platter, W. J., J. D. Tatum, K. E. Belk, J. A. Scanga, and G. C. Smith. 2003. Effects of repetitive
use of hormonal implants on beef carcass quality, tenderness, and consumer ratings of
beef palatability. J. Anim. Sci. 81:984–996.
Prior, R. L. 1983. Lipogenesis and adipose tissue cellularity in steers switched from alfafa hay to
high concentrate diets. J. Anim. Sci. 56: 483-492.
Reinhardt, C. D. 2010. Implant programs affect performance and quality grade. Pages 6-10 in
Kansas State University Cattlemen's Day Report of Progress 1029
http://www.ksre.ksu.edu/library/lvstk2/srp1029.pdf.
Reinhardt, C. D., J. P. Hutcheson and W. T. Nichols. 2006. A fenbendazole oral drench in
addition to an ivermectin pour-on reduces parasite burden and improves feedlot and
carcass performance of finishing heifers compared with endectocides alone. J. Anim.
Sci. 84:2243-2250.
Rhoades, R. D., J. E. Sawyer, K. Y. Chung, M. L. Schell, D. K. Lunt, and S. B. Smith. 2007.
Effect of dietary energy source on in vitro substrate utilization and insulin sensitivity of
muscle and adipose tissues of angus and wagyu steers. J. Anim. Sci. 85: 1719-1726.
Ritchie, H. D. 2002. Connecting the cow herd to the carcass: balancing the production
environment and the marketplace. Michigan State University Beef Cattle, Sheep, and
Forage Systems Research and Demonstration Report. #581:71-78.
Roeber, D. L., N. C. Speer, J. G. Gentry, J. D. Tatum, C. D. Smith, J. C. Whittier, G. F. Jones, K.
E. Belk, and G. C. Smith. 2001. Feeder cattle health management: Effects on morbidity
rates, feedlot performance, carcass characteristics, and beef palatability. Prof. Anim. Sci.
17:39-44.
37
Sainz, R. D., F. De la Torre, and J. W. Oltjen. 1995. Compensatory growth and carcass quality in
growth-restricted and refed beef steers. J. Anim. Sci. 73:2971-2979.
Scheffler, J. M., D. D. Buskirk, S. R. Rust, J. D. Cowley, and M. E. Doumit. 2003. Effect of
repeated administration of combination trenbolone acetate and estradiol implants on
growth, carcass traits, and beef quality of long-fed holstein steers. J. Anim. Sci. 81:23952400.
Schneider, M. J., R. G. Tait, Jr., W. D. Busby, and J. M. Reecy. 2009. An evaluation of bovine
respiratory disease complex in feedlot cattle: Impact on performance and carcass traits
using treatment records and lung lesion scores. J. Anim Sci. 87: 1821-1827.
Schoonmaker, J. P., F. L. Fluharty, and S. C. Loerch. 2004. Effect of source and amount of
energy and rate of growth in the growing phase on adipocyte cellularity and lipogenic
enzyme activity in the intramuscular and subcutaneous fat depots of holstein steers. J.
Anim. Sci. 82:137-148.
Sharman, E. D., P. A. Lancaster, J. T. Edwards, C. L. Goad, G. W. Horn, and G. D. Hufstedler.
2012. Use of dried distillers grains as a supplemental feedstuff and a combination grazing
implant on grazing/finishing performance and carcass merit of wheat pasture stocker
cattle. Prof. Anim. Sci. In Press.
Sharman, E. D., P. A. Lancaster, G. G. Hilton, C. R. Krehbiel, and G. W. Horn. 2009. Effects of
starch- versus fiber-based supplements during winter grazing on growth rate of stocker
cattle and final carcass characteristics. http://www.ansi.okstate.edu/research/researchreports-1/2009/Sharman _Research%20Report%202009%20.pdf.
Sharman, E. D., P. A. Lancaster, G. W. Horn, and G. D. Hufstedler. 2011. Effects of energy
supplementation and a combination grazing implant on grazing/finishing performance
38
and carcass merit of wheat pasture stocker cattle. Plains Nutr. Council Spring Conf.
Publ. p. 114. Texas A&M Research and Extension Center, Amarillo.
Shike, D. W., D. B. Faulkner, M. J. Cecava, D. F. Parrett, and F. A. Ireland. 2007. Effects of
weaning age, creep feeding, and type of creep on steer performance, carcass traits, and
economics. Prof. Anim. Sci. 23:325-332.
Simms, D. D., T. B. Goehring, R. T. Brandt, G. L. Kuhl, J. J. Higgins, S. B. Laudert, and R. W.
Lee. 1988. Effect of sequential implanting with zeranol on steer lifetime performance. J.
Anim. Sci. 66:2736-2741.
Sip, M. L., and R. H. Pritchard. 1991. Nitrogen utilization by ruminants during restricted intake
of high-concentrate diets. J. Anim. Sci. 69:2655-2662.
Slavin, B. G. 1979. Fine structural studies on white adipocyte differentiation. Anal. Res. 195:6372.
Smith, G. C., J. W. Savell, H. R. Cross, Z. L. Carpenter, C. E. Murphey, G. W. Davis, H. C.
Abraham, F. C. Parrish, Jr., and B. W. Berry. 1987. Relationship of USDA Quality
Grades to Palatability of Cooked Beef. J. Food. Qual. 10:269-286.
Smith, G. C., J. W. Savell, J. B. Morgan, and T. E. Lawrence. 2006. Report of the JuneSeptember, 2005 National Beef Quality Audit: A new benchmark for the U.S. beef
industry. Pages 6-11 in Proc. Beef Improvement Federation 38th Annual Research
Symposium and Annual Meeting, Choctaw, MS.
Smith, R. A., K. C. Rogers, S. Husae, M. I. Wray, R. T. Brandt, J. P. Hutcheson, W. T. Nichols,
R. F. Taylor, J. R. Rains, and C. T. McCauley. 2000. Pasture deworming and (or)
subsequent feedlot deworming with fenbendazole. I. Effects on grazing performance,
feedlot performance and carcass traits in yearling steers. Bovine Pract. 34:104–114.
39
Smith, S. B. and J. D. Crouse. 1984. Relative contributions of acetate, lactate and glucose to
lipogenesis in bovine intramuscular and subcutaneous adipose tissue. J. Nutr. 114:792800.
St-Pierre, N. R. 2001. Invited review: Integrating quantitative findings from multiple studies
using mixed methodology. J. Dairy Sci. 84:741-755.
Van Vleck, L. D., A. F. Hakim, L. V. Cundiff, R. M. Koch, J. D. Crouse, and K. G. Boldman.
1992. Estimated breeding values for meat characteristics of crossbred cattle with an
animal model. J. Anim. Sci. 70:363–371.
Vasconcelos, J. T., J. E. Sawyer, L. O. Tedeschi, F. T. McCollum, and L. W. Greene. 2009.
Effects of different growing diets on performance, carcass characteristics, insulin
sensitivity, and accretion of intramuscular and subcutaneous adipose tissue of feedlot
cattle. J. Anim. Sci. 87:1540-1547.
Vassaux, G., D. Gaillard, G. Ailhaud, and R. Negrel. 1992. Prostacyclin is a specific effector of
adipose cell differentiation. Its dual role as a cAMP- and Ca2+-elevating agent. J. Biol.
Chem. 267: 11092-11097.
Waggoner, J. W., C. P. Mathis, C. A. Loest, J. E. Sawyer, F. T. McCollum, and J. P. Banta.
2007. Case study: Impact of morbidity in finishing beef steers on feedlot average daily
gain, carcass characteristics, and carcass value. Prof. Anim. Sci. 23:174-178.
Wagner, J. J. 1988. Effect of previous growing program on the benefits of restricting feed intake
during the finishing phase. Pages 13-15 in South Dakota State University South Dakota
Beef Report http://www.sdstate.edu/ars/species/beef/beef-reports/upload/Cattle_885_Wagner.pdf Accessed August 15, 2011.
40
Wertz, A. E., L. L. Berger, P. M. Walker, D. B. Faulkner, F. K. McKeith, and S. Rodriguez-Zas.
2001. Early weaning and post weaning nutritional management affect feedlot
performance of Angus X Simmental heifers and the relationship of 12th rib fat and
marbling score to feed efficiency. J. Anim. Sci. 79:1660-1669.
Wertz, A. E., L. L. Berger, P. M. Walker, D. B. Faulkner, F. K. McKeith, and S. Rodriguez-Zas.
2002. Early-weaning and postweaning nutritional management affect feedlot
performance, carcass merit, and the relationship of 12th-rib fat, marbling score, and feed
efficiency among Angus and Wagyu heifers. J. Anim. Sci. 80:28-37.
Wiggin, C. J., and H. C. Gibbs. 1990. Adverse immune reactions and the pathogenesis of
Ostertagia ostertagi infections in calves. Am. J. Vet. Res. 51:825–832.
41
Table 1. Mean (Range) for grain content, NEg concentration, and growing phase ADG for steers fed high
versus medium starch, or high versus low starch diets during the growing phase
Dataset 1
Dataset 2
Variable
High Starch
Medium Starch
High Starch
Low Starch
Grain, %
79.4 (70.8 – 89.2) 45.2 (35.0 – 52.0)
72.8 (65.0 – 79.2)
16.4 (0.0 – 35.9)
NEg, Mcal/kg DM
1.42 (1.21 – 1.54) 1.02 (0.62 – 1.22)
1.42 (1.32 – 1.56)
1.03 (0.48 – 1.36)
Growing ADG, kg/d
1.07 (0.76 – 1.51) 1.12 (0.58 – 2.40)
1.30 (0.69 – 1.83)
1.26 (0.77 – 2.07)
Table 2. Meta-analysis of finishing performance and carcass traits from steers fed high- versus
medium-starch growing diets prior to finishing from 9 published studies
Item1
High Starch
Medium Starch
SEM
P-value
Performance
Initial BW, kg
Final BW, kg
ADG, kg/d
DMI, kg/d
Gain:Feed
362.5
527.7
1.50
8.72
0.172
359.2
525.5
1.50
8.80
0.171
Carcass characteristics
HCW, kg
323.9
325.6
2
LM area, cm
82.10
82.28
Rib fat thickness, cm
1.27
1.28
KPH, %
2.70
2.69
Yield Grade
2.94
2.90
2
Marbling Score
426.7
435.7
1
HCW = hot carcass weight, KPH = kidney, pelvic and heart fat.
2
Marbling grid: Slight00=300, Small00=400, Modest00=500.
8.1
16.4
0.10
0.32
0.008
0.21
0.59
0.78
0.62
0.62
10.6
2.39
0.09
0.25
0.18
17.4
0.45
0.78
0.63
0.59
0.50
0.35
42
Table 3. Meta-analysis of finishing performance and carcass traits from steers fed high- versus
low-starch growing diets prior to finishing from 7 published studies
Item1
High Starch
Low Starch
SEM
P-value
Performance
Initial BW, kg
Final BW, kg
ADG, kg/d
DMI, kg/d
Gain:Feed
361.5
532.8
1.76
10.19
0.174
356.5
535.1
1.67
10.29
0.162
Carcass characteristics
HCW, kg
331.8
330.8
2
LM area, cm
77.53
77.95
Rib fat thickness, cm
1.22
1.21
KPH, %
2.42
2.44
Yield Grade
3.02
3.11
Marbling score2
443.1
433.6
1
HCW = hot carcass weight, KPH = kidney, pelvic and heart fat.
2
Marbling grid: Slight00=300, Small00=400, Modest00=500.
13.1
11.4
0.07
0.36
0.010
0.38
0.61
0.09
0.58
0.12
10.2
3.27
0.10
0.27
0.16
19.1
0.77
0.68
0.88
0.75
0.15
0.40
Table 4. Summary statistics of 29 trials used in meta-analysis to evaluate the relationship of
stocker phase ADG and initial finishing BW with carcass characteristics
Variable
N
Mean
Minimum
Maximum
Trial initial BW, kg
79
240.4
186.0
278.0
Stocker ADG, kg/d
85
0.77
0.15
1.68
Initial finishing BW, kg
85
346.7
231.5
450.0
Hot carcass weight, kg
85
326.1
240.2
397.0
LM area, cm2
78
78.80
64.50
96.57
Rib fat thickness, cm
82
1.30
0.51
2.40
Kidney, pelvic and heart fat, %
56
2.16
1.62
3.47
Yield Grade
73
2.99
2.37
4.02
Marbling score1
85
417
266
535
1
Marbling grid: Slight00=300, Small00=400, Modest00=500.
43
Table 5. Regression coefficients (± SE) of carcass characteristics on stocker phase ADG (kg/d), initial finishing BW (kg), or
hot carcass weight (kg) from a meta-analysis of 29 trials
Independent variable
R2
Intercept
HCW1, kg
0.788
0.939
12th rib fat, cm
0.001
0.062
0.734
1.2719 ± 0.0741
1.1751 ± 0.2803
-0.0335 ± 0.2661
0.0106 ± 0.0643*ADG
0.0002 ± 0.0007*initial finishing BW
0.0040 ± 0.0001*HCW
LMA, cm2
0.419
0.695
0.864
75.7086 ± 1.5518
63.5700 ± 3.9409
34.5479 ± 5.1707
4.9965 ± 1.5243*ADG
0.0450 ± 0.0118*initial finishing BW
0.1367 ± 0.0158*HCW
KPH, %
0.341
0.296
0.143
1.9745 ± 0.1144
1.3788 ± 0.2402
1.4338 ± 0.4911
0.2705 ± 0.0977*ADG
0.0023 ± 0.0006*initial finishing BW
0.0023 ± 0.0015*HCW
Yield Grade
0.011
0.075
0.278
2.9268 ± 0.0971
2.6095 ± 0.3618
2.0057 ± 0.4756
0.0073 ± 0.0983*ADG
0.0009 ± 0.0010*initial finishing BW
0.0028 ± 0.0014*HCW
1
310.80 ± 10.95
224.94 ± 23.39
Independent variables
27.4394 ± 9.8434*ADG
0.2931 ± 0.0623*initial finishing BW
HCW = hot carcass weight; LMA = longissimus muscle area; KPH = kidney, pelvic and heart fat.
44
550
Marbling Score
500
450
400
350
300
250
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Stocker ADG, kg/d
Figure 1. Mixed model regression of marbling score (♦) on ADG during the stocker or
backgrounding phase without and with inclusion of other independent variables in the model.
Marbling grid: 300 = Slight00; 400 = Small00; 500 = Modest00. Marbling score (solid line) = 403
± 12.1 + 9.53 ± 9.44*ADG (R2 = 0.048). Marbling score (dashed line) = 311 ± 44.0 + 21.25 ±
7.86*ADG + 69.79 ± 34.35*ribfat (R2 = 0.79). Marbling score (dash/dotted line) = 176.2 ± 55.78
+ 29.36 ± 22.29*ADG – 0.216 ± 0.175*initial finishing BW + 0.604 ± 0.274*HCW + 69.80 ±
28.48*ribfat (R2 = 0.84).
45
550
Marbling Score
500
450
400
350
300
250
200
250
300
350
400
450
500
Initial Finishing BW, kg
Figure 2. Mixed model regression of marbling score (♦) on initial finishing weight without and
with inclusion of other independent variables in the model. Marbling grid: 300 = Slight00; 400 =
Small00; 500 = Modest00. Marbling score (solid line) = 392 ± 23.06 + 0.052 ± 0.060*initial
finishing BW (R2 = 0.034). Marbling score (dashed line) = 282 ± 47.39 + 0.143 ± 0.053*initial
finishing BW + 65.08 ± 34.64*ribfat (R2 = 0.77). Marbling score (dash/dotted line) = 176.2 ±
55.78 + 29.36 ± 22.29*ADG – 0.216 ± 0.175*initial finishing BW + 0.604 ± 0.274*HCW +
69.80 ± 28.48*ribfat (R2 = 0.84).
46
550
Marbling Score
500
450
400
350
300
250
200
250
300
350
400
450
Hot Carcass Weight, kg
Figure 3. Mixed model regression of marbling score (♦) on hot carcass weight without and with
inclusion of other independent variables in the model. Marbling grid: 300 = Slight00; 400 =
Small00; 500 = Modest00. Marbling score (solid line) = 215 ± 93.05 + 0.596 ± 0.290*HCW (R2 =
0.76). Marbling score (dashed line) = 156 ± 51.28 + 0.478 ± 0.160*HCW + 76.29 ± 22.82*ribfat
(R2 = 0.84). Marbling score (dash/dotted line) = 176.2 ± 55.78 + 29.36 ± 22.29*ADG – 0.216 ±
0.175*initial finishing BW + 0.604 ± 0.274*HCW + 69.80 ± 28.48*ribfat (R2 = 0.84).
47
450
Hot Carcass Weight, kg
400
350
300
250
200
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Stocker ADG, kg/d
Figure 4. Mixed model regression of hot carcass weight (♦) on ADG during the stocker or
backgrounding phase with inclusion of initial finishing BW and ribfat in the model. Hot carcass
weight (solid line) = 311 ± 10.95 + 27.44 ± 9.84*ADG (R2 = 0.79). Hot carcass weight (dashed
line) = 154.4 ± 18.83 – 17.60 ± 8.60*ADG + 0.36 ± 0.068*initial finishing BW + 49.91 ±
8.46*ribfat (R2 = 0.94).
48
450
Hot Carcass Weight, kg
400
350
300
250
200
200
250
300
350
400
450
500
Initial Feedlot Placement Weight, kg
Figure 5. Mixed model regression of hot carcass weight (♦) on initial finishing BW with inclusion of ADG
during the stocker or backgrounding phase and ribfat in the model. Hot carcass weight (solid line) = 224.9 ±
23.39 + 0.29 ± 0.062*initial finishing BW (R2 = 0.94). Hot carcass weight (dashed line) = 154.4 ± 18.83 –
17.60 ± 8.60*ADG + 0.36 ± 0.068*initial finishing BW + 49.91 ± 8.46*ribfat (R2 = 0.94).
49