genetic relationship of milk yield for different parities between bulls and their sons
DESCRIPTION
Genetic relationship of milk yield for different parities between bulls and their sons. Objectives. Determine whether bulls differ in maturity rate of their daughters Confirm that those differences are transmitted across generations. Data. - PowerPoint PPT PresentationTRANSCRIPT
2004
2004
2004
H.D. NORMAN,* R.L. POWELL, J.R. WRIGHT, and P.M. VanRADEN
Animal Improvement Programs LaboratoryAgricultural Research Service, USDA, Beltsville, MD
Genetic relationship of milk yield for different
parities between bulls and their sons
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Objectives
Determine whether bulls differ in maturity rate of their daughters
Confirm that those differences are transmitted across generations
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Data
Standardized lactation milk records for Holstein parities 1 through 3
Cows first calving between 1960 and 1998
No missed parities before cow exited herd
Only records from first herd included
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Methods
Three PTA calculated for each bull using current USDA-DHIA animal model
PTA1 based on records from parity 1 of daughters and their contemporaries
PTA1,2 based on records from parities 1 and 2 of daughters and their contemporaries
PTA1,2,3 based on records from parities 1, 2, and 3 of daughters and their contemporaries
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Methods (cont.)
Number of records
n1 = number of bull’s daughters with first parity records
n2 = number of bull’s daughters with second parity records
n3 = number of bull’s daughters with third parity records
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Methods (cont.)
Solutions for biological contributions of parities 2 (PTA2) and 3 (PTA3) derived from 1 1 2 2
1,21 2
nPTA n PTAPTA
n n
+=
+
+ +=
+ +1 1 2 2 3 3
1,2,31 2 3
n PTA n PTA n PTAPTA
n n n
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Results
2864 bulls with genetic evaluations based on 500 daughters
Difference between PTA1 and PTA1,2,3
ranged from 290 to 295 kg of milk; SD of 85 kg
Difference between PTA1 and PTA3
ranged from 610 to 555 kg of milk; SD of 179 kg
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Results (cont.)
PTA1,2 intermediate to PTA1 and PTA1,2,3
(PTA1,2 PTA1) regressed on (PTA1,2,3 PTA1)
b = 0.725, R = 0.971
(PTA2 PTA1) regressed on (PTA3 PTA1)
b = 0.725, R = 0.852
Primarily same genetic control for parities 2 and 3
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Impact of daughter maturity rate
PTA1,2,3 PTA1 (kg)
Number of bulls with PTA1,2 as:
Lowest1
Intermediate1
Highest1
110 0 227 460 to 10
90 314 35
20 to 59 11 274 11210 to 19 106 82 20940 to 11 122 238 6980 to 41 47 402 5
130 to 81 12 369 1130 1 224 0
1Relative to PTA1 and PTA1,2,3
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Correlation between parity PTA for milk
(1996 vs 1999)
Trait r SD of
difference (kg)
PTA1 0.992 27PTA1,2 0.994 31PTA1,2,3 0.994 32PTA2 0.989 45PTA3 0.983 63PTAPublished 0.948 88
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Results (cont.)
16,643 sons with genetic evaluations based on 40 daughters
Expected regressions of son PTA on sire PTA (calculated within sire and son birth year) between 0.44 and 0.50
Actual regressions near expectations
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Regression of son PTA on sire PTA for milk
yield
TraitRegressi
onSE
PTA1 0.440.01
PTA1,2 0.430.01
PTA1,2,3 0.430.01
PTA1,2 PTA1 0.430.01
PTA1,2,3 PTA1 0.430.01
PTA1,2,3 PTA1,2 0.420.02
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Regression of son PTA on sire PTA for milk
yield (cont.)
TraitRegressi
onSE
PTA1 0.440.01
PTA2 0.420.01
PTA3 0.440.01
PTA2 PTA1 0.440.01
PTA3 PTA1 0.450.01
PTA3 PTA2 0.430.03
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Conclusions
Differences in daughter maturity rate are large enough to impact evaluation accuracy, if genetic.
Differences are transmitted from sires to sons (genetic confirmation).
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Conclusions
Modeling separate PTA for each parity should:
Increase accuracy of genetic evaluations
Reduce oscillation in bull evaluations when records per daughter change considerably
Most noticeable in high reliability bulls