Beef Cattle

Selection in Beef Cattle

Overview of Beef Breed Registrations

  • Popular Beef Breeds:
      - Angus
      - Simmental
      - Charolais
      - Hereford
      - Limousin
      - Gelbvieh
      - Shorthorn
      - Speckle Park
      - Other breeds
        - Hays Converter
        - Maine-Anjou
        - Salers
        - Highland
        - Galloway
        - Blonde D’Aquitaine
        - Lowline
        - Dexter
        - Braunvieh
        - Red Poll
        - Tarentaise
        - South Devon
        - Pinzgauer
        - Piedmontese
        - Belgian Blue

Mating Systems

  • Inbreeding:
      - Can result in reduced fertility and calf survival
      - Associated with a relatively high genetic load

  • Crossbreeding:
      - Common practice in commercial cow/calf industry
      - Utilizes complementation and heterosis
      - Benefits include increased fertility and growth

Selection Systems for Beef Cattle

  • Individual Selection:
      - Frequently used in commercial herds
      - Emphasis on selecting replacement heifers
      - Increasing reliance on Estimated Progeny Differences (EPDs)

  • Independent Culling:
      - Most commonly employed for selecting traits related to growth and fertility

  • Index Selection:
      - Particularly useful for selecting breeding bulls

Key Beef Cattle Traits

  • Growth Rate: Includes metrics such as Average Daily Gain (ADG), weaning weight, and yearling weight.

  • Feed Efficiency: Measured using the Dry Matter Intake (DMI), Feed-to-Gain ratio (F:G), and Residual Feed Intake (RFI).

  • Carcass Quality: Evaluated based on marbling, rib-eye area (REA), and yield grade.

  • Meat Quality: Assessed through tenderness and flavor profiles.

  • Reproductive Traits: Includes calving rate, calving interval, and age at first calf.

  • Health Factors: Involves disease resistance and overall health metrics.

  • Structural Soundness: Evaluates conformation and soundness of the cattle.

  • Temperament: Examined through docility and handling characteristics.

Importance of Reproduction

  • A quote by Trenkle and Willham (1977): "Reproduction, or the creation of new wealth, is at least 5 times as important in commercial operations as growth and milk production…"

Female Reproductive Traits

  • Generally exhibit low heritability. Key traits include:
      - Conception Rate: Efficiency of getting pregnant.
      - Calving Interval: Time between calving events.
      - Survivability: Success of calves surviving to weaning.
      - Mothering Ability: Capacity to nurture offspring.
      - Milk Production: Amount of milk produced.
      - Calving Ease: Difficulty of the calving process.
      - Twinning: Incidence of producing twin calves.

  • Correlations:
      - Data from the Canadian Beef Reference Herd (University of Saskatchewan).
      - Negative correlation seen between backfat and superovulation response: $r = -0.66, P = 0.001$.
      - High repeatability observed for number of embryos flushed, exemplified by:
        - Cow 1: 32, 30, 33 embryos
        - Cow 2: 2, 1, 0 embryos

Female Traits - Longevity

  • Production costs decrease with longer cow lifespan.

  • Investments in heifer development are necessary due to higher calving issues in young heifers.

  • Mature cows (between 4-10 years) produce heavier calves.

  • Low heritability values ($h^2 = 0.09 - 0.14$).

Male Reproductive Traits

  • Characteristics Measured:
      - Sperm Count
      - Sperm Morphology
      - Scrotal Circumference:
        - Positively correlated with sperm count, age at puberty, and fertility in offspring.
        - A mature scrotal circumference measurement of > 32 cm at 2 years of age is ideal.
        - Heritability estimates range from $h^2 = 0.4$ to $0.6$ (Söderquist et al., 1991).

Growth Traits in Beef Cattle

  • Heritability Estimates:
      - Birth Weight: $h^2 = 0.30 - 0.40$
      - Weaning Weight: $h^2 = 0.35 – 0.40$
      - Post-weaning Gain (Average Daily Gain - ADG): $h^2 = 0.50 – 0.55$

  • Genetic Correlations:
      - Weaning weight and post-weaning gain: $r = 0.46$.
      - Weaning weight and carcass quality grade: $r = 0.52$.

  • Note:
      - Higher birth weight correlates with increased calving difficulties (dystocia).

Adjusted Weights for Fair Comparison

  • Important factors in correcting weights include:
      - Age: Weaning weights should be adjusted for a standard age of 205 days.
      - Sex Composition: Bulls > steers > heifers in weight.
      - Dam’s Age: Cows under 4 years or over 10 years produce lighter calves.
      - Twins: Twins are approximately 75% the size of single-born calves.

Feedlot Performance Metrics

  • Average Daily Gain (ADG):
      - Heritability estimate: $h^2 = 0.50 – 0.55$.

  • Feed Efficiency:
      - Measured through:
        - Feed-to-Gain Ratio (F:G): The kilograms of feed needed to produce 1 kilogram of gain - lower values are preferred.
        - Gain-to-Feed Ratio (G:F): Opposite of F:G, higher values preferred indicating more gain for the same amount of feed.

Carcass Traits Analysis

  • Quality Grade:
      - Ranges include Prime, AAA, etc.
      - Heritability: $h^2 = 0.40 – 0.45$.

  • Rib-eye Area (REA):
      - Heritability: $h^2 = 0.55 – 0.60$; larger is generally better, within limits.

  • Tenderness:
      - Measured using the Warner-Bratzler shear force indicating the force necessary to cut a section of cooked steak.
      - Heritability: $h^2 = 0.55 – 0.60$.

  • Marbling Score:
      - Heritability: $h^2 = 0.40 – 0.45$ (Bünger et al., 2015).

Quality Grades Overview

  • Carcass Quality Segregation Factors:
      - Age
      - Sex
      - Fat content
      - Muscle distribution
      - Criteria for grading:
        - Canada Prime: Minimum requirements include slightly abundant marbling.
        - Canada AAA: Minimum requirement of small marbling.
        - Canada AA: Requires slight marbling.
        - Canada A: Requires trace marbling; not devoid.

  • Grades Beyond Canada A:
        - D Grade
        - E Grade
        - Additional grading for color and marbling aspects

Yield Grade Definition

  • A measure of the percentage of lean meat in a carcass:
      - Grading System:
        - Canada 1: > 52.3% lean meat.
        - Canada 2: 52.3% to 50.0%.
        - Canada 3: 45.4% to 47.7%.
        - Canada 4: 45.4% to 47.7%.
        - Canada 5: < 45.4%.

  • Notable Trends: The proportion of carcasses grading Canada 1 has decreased, with an increase in AAA and Prime grades.

Testing for Carcass Traits

  • GeneSTAR Marbling Test:
      - Gene involved: thyroglobulin.
      - Patent held by CSIRO (Australia).

  • GeneSTAR Tenderness Test:
      - Evaluates 4 SNPs total associated with tenderness:
        - Calpain
        - Calpastatin

Branded Beef Products

  • Defined by specific criteria:
      - Breed Programs:
        - Example: Certified Angus Beef (CAB)
          - Requirements include an influence of Angus breed and a black coat color.
          - Must meet minimum marbling and REA requirements.
          - Maximum carcass weight set at 1100 lbs.
      - Production Practices:
        - Includes grass-fed beef and organic options.

Vertical Alliances Explanation

  • Cooperation across different sectors of the beef production chain:
      - Example: Cow-calf producers linking to feedlots then to packers.
      - Benefits include price premiums and increased consistency of products.
      - Utilizes grid marketing strategies.