Download
1 / 26
260 likes | 278 Views
Performance Recordin g Guidelines. Chapter 25. Choosing Selection Criteria. Genetics: Heritable variation passed to the next generation. Environment: Management decisions or temporary effects. Phenotype: What the animal looks like. Creep Feeding Maternal environment Drought
E N D
Performance Recording Guidelines Chapter 25
Choosing Selection Criteria Genetics: Heritable variation passed to the next generation Environment: Management decisions or temporary effects Phenotype: What the animal looks like Creep Feeding Maternal environment Drought Forage Type Actual weights Ratios EPDs Indexes Genotype
Selection Criteria • Actual Weights (Just P) • We want to buy good genetics, not good management! • Weight Ratios (P controlled for E within group) • EPDs (Just G) • What we pass on to the next generation, which is then enhanced by the environment we provide that calf
Heritability Heritability informs how we manage cattle! High: REA MARB HCW Low: Milk Heifer Pregnancy Highly heritable-intense selection Lowly heritable-select, but focus on management
Genetic Correlations • Positive • WW and YW • Negative • YW and CED • Favorable • REA and YG (- favorable) • Unfavorable • BW and WW (+ unfavorable)
Genetic Correlations in Action Across-Breed Genetic Trend in BW (top) vs WW (bottom)
Response to Selection • Genetic change per year is a function of: • Selection intensity (i) • Accuracy of selection (r) • Genetic standard deviation ()= • Generation interval (L)
Genetic Change Example = 1 lb./year • Genetic Variance = 230 • Accuracy of 0.3 • Selection Intensity of 1.14 • Generation Interval 5 years
Performance Ratios Individual 205 day adj. WW Contemporary Group Avg. 600 lbs. 500 lbs. Calf was 20% heavier at weaning than the average of his/her contemporaries… X 100 X 100 = 120 Ratio: 120
Central Test Stations • Evaluate bulls from different herds for post-weaning performance with uniform conditions • Test stations assist in: • Locating and evaluating breeding stock belonging to individual producers. • Demonstrating effective testing of post-weaning performance • Providing a source of performance-tested bulls for both commercial and purebred breeders • Assisting in the improvement of economically important traits for beef cattle • Providing access to advanced technology, such as ultrasound (ribeye area, backfat thickness and intramuscular fat percentage), especially for smaller producers that would otherwise not have groups large enough to effectively scan cattle • Providing an educational forum for producers to receive updates on current issues related to the beef cattle industry. Central test stations should be considered as a supplement to good on-farm programs, not as a replacement for them.
Pregnancy Status • Between 50 days and 150 days following breeding, pregnancy status should be determined using rectal palpation or ultrasound • Culling of open cows after this determination is an excellent way to improve herd efficiency
Calving Difficulty • The following scoring system is recommended: • 1 = No difficulty, no assistance. • 2 = Minor difficulty, some assistance. • 3 = Major difficulty, usually mechanical assistance. • 4 = Caesarean section or other surgery. • 5 = Abnormal presentation. These calves are not included when herd averages are calculated because abnormal presentations are not heritable, but should still be reported to the association.
Calving Interval • Calculate yearling calving interval as the number of days between the second-to-last and last calving dates for a particular animal • Cows with consistently long calving intervals may eventually fail to rebreed with fixed breeding season management • Using a lifetime calving interval (the number of days between the first and last calving divided by the total number of calves) is a useful indicator of overall herd reproductive performance
Cow Weight • Record mature cow weight at least once a year • A practical time to record cow weights is at weaning, and it is important that all weights are taken consistently at the same time in the cow’s stage of production • A producer can use cow weight information and other indicator traits, such as body condition to monitor individual or whole herd nutrient requirements.
Udder Suspension and Teat Size • Poor udder and teat confirmation is a major reason why cows are culled from the herd • Udder suspension ranges from 9 (very tight) to 1 (very pendulous) • Teat size scores reflect teat length and circumference from 9 (very small) to 1 (very large) • These scores should be recorded within 24 hours of calving on the weakest quarter and preferably by the same person each time
Breeding Soundness Examination • Classification of bulls – A bull is categorized into one of three classes based on the results of their breeding soundness exam • Satisfactory – meets or surpasses the minimum requirements for scrotal circumference, semen evaluation and physical exam. • Unsatisfactory – fails to meet the minimum requirements for scrotal circumference, semen evaluation and physical exam. • Deferred – does not fit into either the satisfactory or unsatisfactory categories. This bull requires additional maturity or a recovery period to address temporary problems.
