1. Growth, Composition and Meat Quality ANSC 590 ANIMAL GROWTH AND DEVELOPMENT

2. 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)

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

4. Conversion of Muscle to Meat Ante-mortem versus post-mortem conditions of the animal Steps:  Stunning  Exsanguination  Aerobic to anaerobic condition  Glycogenolysis

5. 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.

6. 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

7. 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

8. 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

9. Absence of Fat Cold shortening possibility Age  Negative relationship with increased age  Except with feedlot cattle

10. 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

11. 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

12. 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

13. Double Muscling Muscular hypertrophy- increase fiber size Increase yield and gains Decreased quality and reprod effic. Less connective tissue Increased cold shortening effect

14. 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

15. Repartitioning Agents and Hormone Implants 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