Study Notes on Livestock Evaluation and Meat Production

Appraisal of Market Animals

Objectives

• Determine how age, weight, sex, fatness, and muscling affect the value of livestock.
• Show why some breeds of livestock differ in their ability to deposit fat.
• Relate present-day market conditions to the relative merit of livestock.

Knowledge Necessary to Evaluate Market Animals

1. Relative Merit
2. Market Situation

Relative Merit Defined

Relative Merit is determined by:

• Age
• Weight
• Sex
• Fatness
• Muscling

Factors Affecting Relative Merit

Age

As animals increase in age, they tend to become:

• Less tender
• More flavorful
• Darker in lean color
• Yellow in fat color
• More likely to be diseased
• Fatter
  Note: Not all species are affected equally.

Comparative Effects of Age on Market Value by Species

• Old:Young ratio

ext{Old:Young Value} = rac{ ext{Young Animal Value} imes 100}{ ext{Old Animal Value}}

Old:Young Ratios for Beef, Swine, and Sheep

• Species and Age Impact:
  • Beef: Less tender, more intense flavor, darker lean color, yellow fat color.
  • Swine: Increased fatness.
  • Sheep: Undesirable flavor, higher condemnation rate due to disease.

Summary: Swine are least impacted, while sheep are most impacted with age on market value.

Weight

As animals increase in weight:

• Carcasses become fatter, larger retail cuts.
• Consumer Concerns: Excess fatness and size of cuts may be objectionable.

Sex

Differences in:

• Dressing Percentages
• Carcass Proportions
• Cutability
• Palatability
• Acceptability

Market and Puberty Ages by Species:

• Beef: Market: 18 months; Puberty: 12 months.
• Swine: Market: 7 months; Puberty: 7 months.
• Sheep: Market: 8 months (Spring lamb) or 14 months (old crop lamb); Puberty: 8 months.

Trait Comparison by Species

Key Point: Intact males and females are often priced lower than castrated males, with exceptions in swine.

Fatness

Effects of Fatness:

• Contributes firmness and appearance to cuts.
• Retards cooler shrink and cooking shrink.
• Increases palatability.

Fat Deposition Sequence:

1. Mesenteric
2. Kidney
3. Intermuscular
4. Subcutaneous
5. Intramuscular
   Contribution to Quality: Subcutaneous and intramuscular fat are key for palatability.

Correlation of Subcutaneous Fat to Marbling

• Correlation coefficient: 0.24 (explains about 5.8% of variation)

Source: Boykin et al. (2017); J. Anim. Sci. 95: 3003-3011; doi: 10.2527/jas2017.1544

Muscling

Growth Gradients:

• Starts at extremities (forelimbs and hindlimbs), moves upward and forward, meeting at rib-loin juncture.
• Theories of Selection and Muscling:
  1. Long-bodied, tall stretchy animals are more muscular.
  2. Selecting for heavy muscling in certain areas affects overall muscle growth in correlated areas.
  3. Muscle always present in a constant ratio to bone; disproves the theory of selection affecting muscle ratios.

Muscle:Bone Ratios by Type:

• Thinly muscled: 2.5:1
• Normally muscled: 3.5:1
• Thickly muscled: 4.5:1
• Double muscled: 5.5-8.5:1

Interactions between Fatness and Muscling on Cutability

USDA Slaughter Animal and Carcass Grades

Objectives

• Translate evaluations of age, weight, sex, fatness, and muscling into market descriptions.
• Determine importance of grades to animal agriculture.
• Demonstrate factors in quality and quantity evaluations of animals and carcasses.

Grades Defined

Groups of livestock with similar market desirability related to carcass predictions.

Factors Influencing Carcass Value

Carcass value is contingent upon:

• Age
• Weight
• Sex
• Fatness
• Muscling

Ease of Description: Weight and sex are simply described; age, fatness, and muscling have complex combinations.

Historical Context

In the early 1920s, common terminology was developed for:

• Market news reporting
• Transactions sight unseen

Estimated Palatability Grades

• Beef: Prime, Choice, Select, Standard, Commercial, Utility, Cutter, Canner.
• Pork: U.S. and U.S. Utility.
• Lamb: Prime, Choice, Good, Utility, Cull.

Estimated Cutability Grades

• Beef: 1, 2, 3, 4, 5.
• Pork: 1, 2, 3, 4.
• Lamb: 1, 2, 3, 4, 5.

Grading Concepts

• Once the purpose is determined, specific traits are used to categorize carcasses into homogeneous groupings (A, B, etc.).
• Grading Schemes:
  • Dichotomous: Acceptable and Unacceptable.
  • Hierarchical: Superior, Good, Average, Inferior.

Original Concepts of Beef Carcass Grading

• Developed for elite consumers (taste-focused) and retail consumers (taste and leanness).
• Prime for elites, Choice, Select, and Standard for retail;
• Commercial, Utility, Cutter, and Canner for processing needs.

Cutability Grades Development

• Established in the 1960s to accurately segment carcasses based on yield of closely trimmed retail cuts.
• Factors include:
  • Size: Carcass weight.
  • Muscling: Ribeye area and score.
  • Trimmable Fat: Adjusted fat thickness at ribs.

Impact of Fatness and Muscling on Retail Cuts

• Fatness increases, retail cut yield decreases.
• Muscling increases, retail cut yield increases.

Growth and Development of Meat Animals

Objectives

• Discuss producing desirable carcasses through full feeding and proper marketing.
• Show nutrient utilization priorities affecting growth and development.
• Demonstrate importance of growth curves in slaughtering optimal livestock.

Strategies for Desirable Carcasses

1. Full Feed
2. Market at readiness
3. Avoid excessive holding before slaughter

Reason for Full Feeding

• Well-bred animals with high growth potential are most efficient on high nutrition diets.

Nutrient Utilization Priorities

Tissues by importance:

Optimal Tissue Proportions

Optimal proportions generally attained at:

• 1,300 pounds for cattle,
• 280 pounds for swine,
• 120 pounds for lamb.

Differences in Slaughter Timing

Differences in optimal weights and ages between sex classes and breeds due to hormonal activity and maturity.

Marbling and Adjusted Fat Thickness

Marbling Classifications:

• Small Frame:
  • Marbling: Small
  • Finished by 900 pounds
  • Adjusted fat thickness: 0.50 inch
• Medium Frame:
  • Marbling: Slight
  • Finished by 1,100 pounds
  • Adjusted fat thickness: 0.40 inch
• Large Frame:
  • Marbling: Traces
  • Finished by 1,300 pounds
  • Adjusted fat thickness: 0.30 inch

Impact of Holding Animals too Long

Consequences of Excessive Weight:

• Decreased rate of gain
• Decreased feed efficiency
• Undesirable carcass composition

Feed Efficiency and Offsetting Undesirable Fat Deposits

Pounds of Feed Required:

• Excess feed for undesirable components leads to inefficiency.

Objective Evaluations of Meat Animals

Objectives

• Discuss necessity for objective evaluations of meat animals.
• Show mechanisms of objective methods determining carcass composition.
• Familiarize with methods for carcass composition assessment.

Issues with Evaluation Accuracy

• Current expert evaluations are only about 60% accurate in assessing market animals and breeding stock.

Live Evaluation Methods

To predict cutability, essential to assess:

• Amount of subcutaneous fat
• Amount of muscle

Predicting Techniques

1. Ultrasonics: High-frequency sound waves used for fat thickness at 12th rib and ribeye area.
2. Optical Probes: Tools like Hennessy Grading Probe and Fat-O-Meater.
3. Antipyrine Distribution: Related to body water and fat.
4. Anesthetic Techniques: Behavior in fat vs. lean tissues.
5. K40 Counter: Gamma radiation measurements for muscle content.
6. Scanning Technologies: CT scans and MRIs.
7. Total Body Electrical Conductivity (ToBEC): Conductivity levels fluctuate based on fat percentage in the body.
8. Video Image Analysis (VIA): Used for overall carcass assessment.

Whole Body Specific Gravity Equation

ext{Specific Gravity} = rac{ ext{Weight in Air}}{ ext{Weight in Air} - ext{Weight in Water}} imes 100

Contribution of Meat in the Diet

Objectives

• Define the role of red meat in dietary guidelines.
• Discuss nutrient composition of red meat.
• Address trials involving lean meats in cholesterol-lowering diets.

Dietary Guidelines for Americans (2015-2020)

• Max 6 ounces cooked lean meat, poultry, fish daily; preferably lean cuts.
• Trim fat from meat; skin off poultry.

Meat Consumption Data

• Daily Average: 2.5 ounces of meat per day.
• Breakdown includes various meat forms and cuts.

Consumer Preferences

• Move toward closer-trimmed beef products due to leaner demands.
• Consumers prefer marbling for flavor but reject waste fats.

The “Window of Acceptability” Concept

Based on findings by Savell and Cross (1988):

• Minimum 3% raw marbling fat needed for acceptable palatability.
• Increased marbling above 3% leads to slight increases in palatability, with further thresholds at 5% and 7%.

Diet Trends Featuring Meat

• Low-Carb Diet
• Keto Diet
• Gluten-Free Diet
• Paleo Diet
• Carnivore Diet

Key Nutrients from Meat

• Iron: Heme iron from meat is more absorbable than nonheme iron from plants.
• Vitamin Influence: Vitamin C helps iron absorption while some items block it (coffee, tea, spinach).

Exam Review - Beef Slaughter

Identifying Concepts & Objects

1. Immobilization Method: Specify used stunner.
2. Identify key objects and their functions.
3. Define abnormal fat appearances, effects of withholding feed before slaughter, and causes of dark cutting in meat.

Calculations to Remember

• Dressing Percentage = rac{ ext{Dressed Carcass Weight}}{ ext{Live Weight}} imes 100
• Carcass Cost Basis = rac{ ext{Live Price Per Cwt}}{ ext{Dressing Percentage}} imes 100

Yield Calculation Knowledge

• Factors for yields, including fat thickness and ribeye area and their effects on pricing and yield of retail cuts.

Identifying Primal Cuts

• Know the breakdown of hindquarter and forequarter, including major and minor cuts, along with practical lab knowledge for beef fabrication.