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Growth, Composition and Meat Quality

Growth, Composition and Meat Quality

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Growth, Composition and Meat Quality

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  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