seventeendairy - Dairy Cattle Genetics ANS 3384...

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Dairy Cattle Genetics ANS 3384
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Heritabilities of Traits of Dairy Cattle Trait Heritability, % Milk Yield 25 Fat % 45 Protein % 60 Udder Traits 30 35 Feet and Leg Traits 10 35 Other Structural Traits 20 50
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Heritabilities of Additional Traits Trait Heritability, % Longevity < 10 Milking Speed 20 - 25 Temperament 10 - 15 Calving Ease 5 – 15 Fertility 0 - 10
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Dairy Genetic Jargon PTA - Predicted Transmitting Ability A measure of additive genetic value relative to a base year of birth Useful to rank sires for milk, fat, protein yield Example: The daughters of a bull that has 2500 lb PTA-Milk will be expected, on average, to milk 1000 lb more than daughters of a bull with 1500 PTA-Milk
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Dairy Genetics Jargon Reliability Measure of the Accuracy of the PTA Reported as a %, 0 – 99 Based on the number of daughters a bull has with production records Low Reliability values indicate that the PTA of the bull will likely change as more daughters are evaluated
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Calculation of PTA-Milk PTA-Milk = w 1 (PTA S + PTA D )/2) + w 2 (Yield Deviation/2) +w 3 (2PTA progeny - PTA mates ) Where: w 1 = 1 for calves of both sexes and 0 for bulls with many progeny w 2 is dependent upon the number of days milked and is always 0 for bulls w 3 is dependent on the number of progeny
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w 1 ((PTAS + PTAD)/2) This is simply the pedigree info It represents all we have available in both bulls and heifers as calves w 1 starts as 1 in calves and can be nearly 0 in bulls with many progeny
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w 2 (Yield Deviation/2) This second part of the formula is based on milk production in cows, w 2 is always 0 in bulls and becomes larger as a cow milks for longer periods of time
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+w 3 (2PTA progeny - PTA mates ) This is the progeny part of the equation—the mates’ part is included to adjust for the fact that some bulls are bred to better cows than others w 3 approaches 1 when bulls have many progeny
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Recommendations for the Use of Young Bulls with Low (65 - 80%) Reliabilities Use only bulls with very high PTA values Use a relatively large number of young bulls and use each bull sparingly (perhaps <30 units per bull) The PTA values of some of these bulls will rise
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This note was uploaded on 07/16/2011 for the course ANS 3384 taught by Professor Olson during the Spring '09 term at University of Florida.

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seventeendairy - Dairy Cattle Genetics ANS 3384...

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