Genetic parameter estimates in the South African Jersey breed

Author: J. duToit, J.B. van Wyk and J. van der Westhuizen
Year: 1998
Issue: 3
Volume: 28
Page: 146 -

Data obtained from the INTERGIS for Jersey breeders participating in the NationalDairy Cattle Performance and Progeny Testing Scheme were analysed. The registered and grade records commenced in test year 1977 through 1992 (incomplete) and consisting of lactations between 240 and 300 days, were considered as normal completed records. Five production traits were evaluated, ie. milk, fat and protein yields and fat and protein percentages for first and second lactation records. Variance components and resulting heritability estimates were obtained by DFREML procedures using 45 240 first and 27 414 second lactation records. The heritability estimates for first lactation milk, fat and protein yields and fat and protein percentages were 0.35, 0.35, 0.34, 0.57 and 0.58 respectively. Corresponding estimates for second lactation traits were 0.29, 0.28, 0.28, 0.53 and 0.56. Repeatability estimates, calculated as interclass correlations when only two records per animal are available, were 0.73, 0.72, 0.74, 0.71 and 0.74, respectively, for the production traits considered. The heritability estimates were in agreement with literature results, indicating that selection for all five traits would be effective. It was suggested that an increase in environmental effects may be partly responsible for lower estimates of heritability of second lactation traits. The results indicate that selection of dairy bulls can be based on first parity records.

Keywords: heritability estimates, Jersey, production traits, variance components
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