Development of the Ruminant
Digestive Tract
Readings:
Quigley and Drewry 1998. Nutrient and Immunity Transfer from Cow to Calf Pre- and
Post-Calving. J Dairy Sci 81:2779-2790
http://jds.fass.org/cgi/reprint/81/10/2779.pdf
Quigley et al. 2001 Formulation of Colostrum Supplements, Colostrum Replacers and
Acquisition of Passive Immunity in Neonatal Calves J. Dairy Sci 84:2059-2065
http://jds.fass.org/cgi/reprint/84/9/2059.pdf
Beharka et al. 1998. Effects of Form of the Diet on Anatomical, Microbial, and
Fermentative Development of the Rumen in Neonatal Calves. J.Dairy Sci 81:19461955.
http://jds.fass.org/cgi/reprint/84/9/2059.pdf
Longenbach and Heinrichs. 1998. A Review of the Importance and Physiological Role
of Curd Formation in the Abomasum of Young Calves. Anim. Feed Sci Tech 73:8597.
Blum, J.W. 2006. Nutritional physiology on neonatal calves. J. Anim. Phys and Anim. Nut. 90:111.
Transition from birth to functional ruminant
• Phases
– Birth to 3 weeks
• True nonruminant
– 3 weeks to approximately 8 weeks
• Transition
• Length is diet dependent
– Beyond 8 weeks
• Ruminant
• Changes
–
–
–
–
–
Absorption
Function of the reticular groove
Enzyme activity of saliva and lower GI tract
Development of rumen volume and papillae
Development of rumen microflora
Changes in absorption
• Calves born with no maternal gamma-globulins, and,
therefore, must receive them from colostrum
• Composition
Colostrum
Milk
Fat, g/kg
36
35
Non-fat solids, g/kg
185
86
Protein, g/kg
143
32
Immunoglobulins
55-68
.9
Lactose
31
46
Ash, g/kg
9.7
7.5
Ca, g/kg
2.6
1.3
P, g/kg
2.4
1.1
Mg, g/kg
.4
.1
Carotenoids, ug/g fat
25-45
7
Vitamin A, ug/g fat
42-48
8
Vitamin D, ug/g fat
23-45
15
Vitamin E, ug/g fat
100-150
20
Non-nutritive biogenic substances (Insulin, IGFs, Growth
hormone, thyroxine, glucagon, prolactin, cytokines)
Factors affecting the concentration of
immunoglobulins in colostrum
•
•
•
•
Number of milkings
Colostrum volume
Increased ambient temperatures
Dietary crude protein content during gestation
– No effect on concentration of immunoglobulins in
colostrum
– Reduces absorption of immunoglobulins by calf.
Serum Immunoglobulin concentrations
• 10 g/l serum in calves is recommended
– A 1996 NAHMS study found that 40% of dairy heifers
had less than the recommended level.
• Reasons for inadequate levels of IgG
– Inadequate colostrum consumption
• Recommended that calf receive a minimum of 3 to 3.8 L of
good quality colostrum within 1 hour after birth.
– Supply 100 g IgG
– Reduced IgG absorption
Factors affecting IgG absorption
• Age at first colostrum feeding
– The ability to absorb whole immunoglobulins
decreases rapidly after birth
• Reasons
– Maturation of the epithelium
» Epithelium is totally replaced in first 24 hours after birth
» Result of gene activation and vascularization
» Modulation
Ingested nutrients
Regulatory substances produced and acting within GIT
– Development of GI tract proteolytic activity
• Should feed enough colostrum to supply 100 g IgG as early
as possible
• Sex of calves
– Heifers have higher IgG than bulls
• Cattle breed
– Holsteins have more efficient Antibody Absorption Efficiency
(AEA) than Ayrshires
• Method of feeding
– Feeding with nipple pail results in higher serum antibodies
than nursing because:
• Nursing calves consume colostrum later than nipple-fed calves
• Nursing calves consume less colostrum than nipple-fed calves
– Esophageal feeding of colostrum reduces AEA because
• Colostrum is retained in the rumen for 2 to 4 hours
– AEA is greater in calves fed colostrum in 2 feedings than 1
feeding
Factors affecting IgG absorption (Cont.)
• Metabolic or respiratory acidosis reduces AEA
– Causes of metabolic acidosis
• Dystocia
• Low Cation:Anion balance in diet of dam during pregnancy
• Extremely cold ambient temperatures reduce AEA
• Increased plasma glucocorticoids will increase AEA
• Increased serum colostrum IgG concentrations will
increase AEA
– AEA can be improved in low to medium quality colostrum by
adding bovine serum protein
• Reasons
– Overcome competition with other proteins
– There may be factors in colostrum that stimulate closure of the
epithelium to antibody absorption
Change in the function of the reticular groove
• Reticular groove is composed of two lips of
tissue that run from the cardiac sphincter to the
reticulo-omasal orifice
• Purpose
– Transport milk directly from the esophagus to the
abomasum
• Reflex
– Action occurs in two movements
• Contraction of longitudinal muscles that shorten the
groove
• Inversion of the right lip
– Neural pathway
• Afferent stimulation by the superior laryngeal nerves
• Efferent pathway by the dorsal abdominal vagus nerve
Stimuli for contraction of the reticular groove
•
•
•
•
Suckling
Consumption of milk proteins
Consumption of glucose solutions
Consumption of sodium salts
– NaHCO3
– Effective in cattle, but not sheep
• Presence of copper sulfate
– Effective in lambs
Effects of age on reticular groove reflex
• Reflex normally equal in bucket-fed and nipplefed calves until 12 weeks of age
– Reflex normally lost in bucket-fed calves by 12 weeks
– Reflex normally lost in nipple-fed calves by 16 weeks of
age, but effectiveness decreases
• Considerable variation
• Advantages of nipple-feeding compared to
bucket-feeding
– Positioning of calf
• Arched neck
– Rate and pattern of consumption of milk
• Slower and smaller amounts consumed
– Increased saliva flow
Nutritional implications of the reticular groove
• More efficient use of energy and protein
– No losses of methane, heat of fermentation or ammonia
– Efficiency
DE-ME
ME-NEm ME-NEg
Preruminant
96
86
69
Ruminant (fed starter grain)
88
75
57
• Require B vitamins
• Unable to utilize nonprotein nitrogen
Changes in digestive enzymes
• Proteases
– Pepsin
• May or may not be secreted as pepsinogen by
newborn calf
• HCl secretion is inadequate in newborn calf to lower
abomasal pH enough for pepsin activity
• Calf born with few parietal cells
– Number of parietal cells increase 10-fold in 72 hr
– Number of parietal cells reach mature level in 31 days
– Pancreatic proteases
• Activity is low at birth
• Activity increases rapidly in first days after birth
• Mature levels of pancreatic proteases reached at 8 to
9 weeks after birth
Effect of age on the volume and composition of
gastric and pancreatic secretion
Age (days)
7-10
Estimated apparent secretion
(Saliva, gastric, and bile)
Volume (l/12 hr)
Cl- minus Na+ (mmol/l)
Pancreatic
Secretion (ml/l diet)
Trypsin activity (mg/l diet)
Total protease (g/l diet)
24-31
63-72
2.2
95
2.2
140
2.7
122
88
42
.3
107
42
.7
122
45
1.0
– Rennin
• A protease secreted by the abomasum
– Activity low at birth, but increases rapidly
• Actions
Proteolytic activity
Curd formation
pH optima
Rennin
Pepsin
3.5
2.1
6.5
5.3
• Curd formation
–
–
–
–
Forms within 3 to 4 minutes
Slows rate of passage to increase digestion
Specific for the protein, casein
Implies that use of proteins other than casein in milk
replacers may result in digestive upset and reduced
growth
» Necessity somewhat controversial beyond 3 weeks of
age
– Low temperature ultrafiltration processing has produced
acceptable whey protein concentrates
Effects of feeding non-milk proteins in milk
replacers
•
•
•
•
•
•
Less gastric secretion
Less gastric and pancreatic proteolytic activity
Less coagulation
Increased rate of gastric emptying
Reduced protein digestibility
Putrefactive scours
– Undigested protein
– Development of Coliform bacteria
– Results
• Damage to intestinal mucosa
• Increased osmotic pressure in digesta from amines
– Diarrhea
– Alkaline pH
• Particularly a problem before 3 weeks of age
Use of non-milk protein sources in milk replacers
• In 1995, only 11% of milk replacers contained only casein
because of cost of casein containing ingredients
• Substitution levels
Digestibility Substitution
Whey
Soy flour
Soy protein concentrate
CP, %
40-90
50
70
(3 wk)
61-67
51
73-89
for casein
Up to 100%
20%
40 to 100%
• Performance of calves fed milk replacers with different protein
sources
Age, wk
0-6
4-15
0-10
0-6
0-9
0-9
0-8
0-6
Casein
13.8 kg
199.1 kg
.42 kg/d
20.6 kg
23.2 kg
.54 kg/d
20.4 kg
.19 kg/d
Daily gain
Soy protein conc
2.8 kg
74.6 kg
.09 kg/d
Whey protein conc
12.5 kg
26.5 kg
.56 kg/d
20.3 kg
.25 kg/d
Rationale for efficacy of utilization of non-milk
proteins in milk replacers
• Factors affecting gastric emptying of digesta
– Coagulation of milk proteins
– Fat content of diet
• Fat in duodenum will stimulate cholecystokinin
– Presence of glucose in duodenum
– Presence of amino acids in duodenum
• Processing and compositional factors affecting milk
replacer protein utilization
– Heating
• Excessive heating inhibits protein coagulation
– Fat content of diet
• Fat (40% of the DM) may improve clotting
• High fat levels may stimulate diarrhea by themselves
– Fat processing of diet
• Low temperature dispersion may result in more effective protein
use than homogenization
MILK REPLACER PROTEIN SOURCES
Preferred
Acceptable as
partial substitute
Marginal
Dried whey protein
concentrate
Soy protein isolate
Soy flour
Dried skimmilk
Protein modified
soy flour
Modified potato
protein
Casein
Soy protein
concentrate
Dried whey
Animal plasma
Dried whey product
Egg protein
Modified wheat
protein
Changes in digestive enzymes
• Carbohydrases
– Intestinal lactase
• Activity high at birth
– Stimulated by feeding IGF-1
• Decrease in activity after birth is diet dependent
– In ruminant calves, activity drops to mature levels by 8 weeks of age
– In pre-ruminant calves, activity at 8 weeks is 10x greater than
ruminant calves
– Pancreatic amylase
• Activity is low at birth
• Activity increases 26x by 8weeks of age
• Mature levels not reached until 5 to 6 months of age
– Intestinal maltase
• Low at birth
• Increases to mature levels by 8 to 14 weeks of age
– Independent of diet
– Intestinal sucrase
• Never any sucrase
• Fructose is not absorbed
Implications of changes in carbohydrases
• Digestibility
Lactose
Maltose
Starch
Sucrose
• Fermentative scours
Digestibility (28 days)
95
90
50-80
25
– Undigested carbohydrates stimulate excessive production of
VFAs and lactic acid which cause diarrhea
– Feces have an acidic pH
– Causes
• Non-lactose carbohydrates in milk replacers
• Overfeeding lactose as milk or milk-based milk replacer
Changes in digestive enzymes
• Lipases
– Pregastric esterase
• Secreted in the saliva until 3 months of age
• Activity is dependent on method of feeding and
composition of feed
– Activity is increased by nipple-feeding
– Activity is greater in calves fed milk than those fed hay
• Hydrolytic activity is adapted to milk fat
– Specifically releases C4 to C8 fatty acids from triglycerides
– Equal activity to pancreatic lipase for C10 to C14 fatty acids
– No activity on longer chain fatty acids
• Although secreted in saliva and the pH optimum of PGE is
4.5 to 6, most PGE activity occurs in the curd in the
abomasum
– 50% of the triglycerides in milk is hydrolyzed within 30
minutes
• Importance of PGE is questionable
– Pancreatic lipase
• Secretion is low at birth
• Increases 3x to mature levels by 8 days
• Hydrolyzes both short and long chain fatty acids
Implications of the lipase activity in
preruminants
• Preruminants can make effective use of a variety
of fats
Digestibility
Butterfat
97
Coconut oil (Can’t be fed alone)
95
Lard
92
Corn oil
88
Tallow
87
Additional considerations with fats in milk
replacers
• Fat must be emulsified to a particle size less than
4 um with lecithin or glycerol monostearate
• Vitamin E and/or antioxidants must be
supplemented if unsaturated fatty acids present
• Fat in replacers may reduce diarrhea
– Fat reduces concentration of lactose and protein
– Fat reduces rate of passage
• Increasing fat concentration in a replacer may
increase calf fat reserves for early weaning
Metabolic changes occurring as a
preruminant develops into a ruminant
• Energy source
Energy source
Glucose
Fat
VFAs
•
Fetus
Calf
Cow
Blood glucose
•
Blood glucose, mg%
Calf
100
Cow
60
Liver enzymes associated with glucose utilization decrease
– Enzymes involved in glycolysis
• Fructose-1,6-diphosphate adolase
• Glucose 3 phosphate dehydrogenase
– Enzymes involved in pentose phosphate shunt
• Glucose-6-phosphate dehydrogenase
• 6 phosphogluconate dehydrogenase
– Enzymes involved in fatty acid synthesis from glucose
• Citrate lyase
•
Liver enzymes associated with gluconeogenisis increase
– Glucose-6-phosphatase
– Fructose diphosphatase
Changes in rumen size and papillae
• As a preruminant animal develops, the relative
size of the reticulorumen and omasum increases
while that of the abomasum decreases
1
Reticulorumen
Omasum
Abomasum
34
10
56
Age, wk
3
5
14
Adult
% of stomach weight
48
65
70
64
16
12
18
25
36
23
12
11
• Factors affecting development of the ruminant
stomach
– Age
– Diet
Effects of diet on development of rumen
• Chemical effect
– Volatile fatty acids produced during carbohydrate fermentation
cause development of rumen epithelium and papillae
– Mechanism
• Volatile fatty acid metabolism in the epithelium
– Metabolism of butyrate to acetoacetate and Beta-OH-butyrate causes
hypoxia which stimulates blood flow and nutrient transport
• Volatile fatty acids stimulates insulin secretion
– Insulin stimulates DNA synthesis
• Moderate levels of volatile fatty acids stimulates mitosis
• Increased volatile fatty acids in the epithelium increases osmotic
pressure in cells
– Effect (20 wk old calves)
Diet
Chopped hay, kg wet
%
Concentrate, kg wet
%
Tissue
Epithelium Muscle
1.2
.8
57.7
42.3
2.5
.9
74.3
25.7
– Implications of the effects of volatile fatty acids on
epithelial development
• For early weaning programs, a starter concentrate should
be offered as early as possible
• Calves should not be weaned until they are consuming 1 lb
starter/day
Effects of diet on development of rumen
• Physical form of diet
– Volume
• Addition of bulk or fiber stimulates the rate of increase in
stomach volume
Newborn
13 weeks
Milk only
Concentrates
Hay
Mixed hay-concentrate
Volume, l
Reticulorumen Omasum Abomasum
1.5
.1
2.1
7.4
30.0
37.1
28.2
.2
.9
1.2
1.8
3.2
2.5
3.8
3.1
• Presence of fiber in the diet does not affect mature volume
– Normal epithelial and papillae structure
• Inadequate long fiber results in:
– Parakeratosis of rumen epithelium
– Branched papillae
Fine
Empty weight, g
Reticulorumen
Omasum
Abomasum
Mucosal layers, um
Keratin
Total epithelium
Muscle layers, um
Inner
Outer
Papillae
Length, um
Width, um
% Branched
Hay
Intermediate Course
994
338
386
904
225
422
931
211
296
16
53
11
79
6
75
933
688
1005
799
2218
311
25
1621
273
16
1062
736
1097
280
12
•Implication
•Adequate long fiber is
necessary in the diet of
the growing calf to
ensure normal epithelial
and papillae growth
Development of rumen microflora
• At birth, rumen contains no microorganisms
• Normal development pattern
Appear
5-8 hours
Peak
4 days
½ week
½ week
½ week
3 weeks
5 weeks
6 weeks
Organisms
E. Coli, Clostridium welchii
Streptococcus bovis
Lactobacilli
Lactic-acid utilizing bacteria
Amylolytic bacteria
B. ruminicola – week 6
1 week
6 to 10 weeks Cellulolytic and Methanogenic
bacteria
Butyrvibrio – week 1
Ruminococcus – week 3
Fibrobacter succinogenes – week 6
1 week
3 weeks
-
12 weeks
Proteolytic bacteria
5 to 9 weeks Protozoa
9 to 13 weeks Normal microbial population
Factors affecting development of rumen
microbial population
• Presence of the organisms
– Normal population of bacteria and protozoa is established by
animal-to-animal contact between ruminant and preruminant
animals
– Bacteria will still establish if calves are kept separate from
mature animals.
• Protozoa will not
• Favorable environment for growth
– Presence of substrates
• Includes intermediate substrates
–
–
–
–
–
CO2
Ammonia
H2
Branched-chain VFA
Aromatic growth factors
» Phenylpropanoic acid
– B vitamins
– Increased ruminal pH
– Digesta turnover
25% alfalfa hay:75% grain
Age, weeks
2
4
6
Rumen pH
Fine
6.25
5.35
5.6
Chopped
6.65
5.70
6.0
Amylolytic bacteria, x 1010 /gm DM
Fine
Chopped
1.05
1.2
1.3
.2
1.1
1.2
Cellulolytic bacteria, x 106/gm DM
Fine
.09
.3
30
Chopped
.18
2.0
100
