Growth, Composition
and Meat Quality
ANSC 590 ANIMAL GROWTH
AND DEVELOPMENT
USDA GRADING


Quality versus Yield
Definition(s)- provide uniform standards
 Table
12.1
 Factors Affecting Quality Grades



Kind, Class and Grade
Maturity (Figure 12.2)
Marbling relationship to palatability
 Poultry
(Table 12.2)
 Yield/Cutability (Table 12.3)
Yield Grade Relationships

Fat, muscle and bone relationships
 Figure
12.14
Regression models versus short-cut
calculations
 Anatomical measurements for
compositional traits
 Ex. Pork percent muscle, Beef yield grade

Conversion of Muscle to Meat
Ante-mortem versus post-mortem
conditions of the animal
 Steps:

 Stunning
 Exsanguination
 Aerobic
to anaerobic condition
 Glycogenolysis
Conversion of Muscle to Meat
ATP to ADP , thus energy expended
 Pyruvate converted to Lactate and
ultimately lactic acid
 Progressive reduction in pH
 Deviations of normal post-mortem
metabolism

 Dark
cutters, PSE, etc.
Meat Tenderness
Little can be gained by improvement of
animal growth if the resulting quality of the
endproduct is undesirable to the consumer
 Connective Tissue- collagen

 As
animals mature crosslinkages increase
resulting in more stability, yet tougher and
stronger collagen bonds thus decreases
solubility and reduces gelatinization
Meat Tenderness

Myofibrillar Protein Interactions
 Degree
of overlapping structures within
actinomyosin formation resulting in varying
sarcomere length
 Proteolytic activity

Calpain enzyme system are responsible for
destruction of myofibrils
Quality versus Quantity


Figure 12.23
Sex/gender variations within growth and
development-biological maturity
 Intact males have:
 Less fat as well as less firmness of fat
 Increased protein, myoglobin, red color, yields
 Increased off-odors due to increased steroid metabolism
synthesized by the gonads, stored in the salivary glands,
released by the saliva ingested and deposited in the fatty
tissue
 Skatole is a fat-soluble cmpd from tryptophan metabolism in
the hind gut esp. in swine and is correlated to the off-odor
Absence of Fat
Cold shortening possibility
 Age

 Negative
relationship with increased age
 Except with feedlot cattle
PSS in pork

Rendement Napole Gene
 Acid
meat
 Responsible for glycolytic potential index
 AMPK- adenosine monophosphate-activated protein
kinase which is responsible for synthesizing glycogen
 If this ability is lost and glycogen is accumulated at a
higher rate this produces more lactate and ultimately
results in more acid meat upon rigor mortis
completion
PSS pork

Halothane Gene
 Extremely lean pigs
 Incapable of handling stress
 Malignant hypothermia along
with cyanotic (blue),
lethargic, increased respiration, and increased core
body temp
 Characterized by a severe reaction when exposed to
halothane gas
 Positive pigs possess a mutated calcium release
channel located in the SR. This is known as
ryanodine receptor
PSS pork

Halothane cont.
 Increased
metabolism is a result of increased
ctyoplasmic calcium in early postmortem. This
stimulates increases in glycogen phosphorylase
which speeds up glycogen breakdown.
 This increased rate of metabolism then increases the
rate of pH decline when carcass temps are elevated
 This ultimately reduces the water holding capacity
Double Muscling
Muscular hypertrophy- increase fiber size
 Increase yield and gains
 Decreased quality and reprod effic.
 Less connective tissue
 Increased cold shortening effect

NUTRITION



Delayed feedlot gains will decrease tenderness
Shorter periods of feeding high energy will
results in lower quality aspects
Connective Tissue concentration remains
constant with increased growth rates
 Due
to increased proteases
 Lacks excessive cross-linking
 More soluble collagen matrices
 Do not remove high energy too long before slaughter

this may result in Dark Cutters
Repartitioning Agents and
Hormone Implants

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Table 12.7 and 12.8
Somatotropin
Beta-agonists
Hormones- estrogen, progesterone,
testosterone
Effects on tenderness Table 12.9
Effects on sensory perceptions Table 12.10