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Journal of Dairy Science Vol. 69 No. 4 1087-1092
© 1986 by American Dairy Science Association ®
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Estimating Genetic Values for Milk Production in the Tropics1

B. Y. Abubakar2, R. E. McDowell, K. E. Wellington3 and L. D. Van Vleck

Department of Animal Science, Cornell University, Ithaca, NY 14853

ABSTRACT

Variance components and predicted sire values were estimated using 305-d projected and unprojected milk records of varying lengths. Original data consisted of 15,512 lactation records of daughters of 138 Jamaica Hope sires that calved between 1969 and 1981 in 38 commercial dairy herds in Jamaica. Classification of records had little effect on components of variance. Herd-year-season variance decreased from 36% using all lactations to 28% with first lactations only. Sire variance was consistently about 10%. Cow component of variance accounted for 17% of the total variation using all lactations and 36% using all lactations of cows with recorded first lactations. Heritabilities for milk by Henderson's method 1 were five to six times larger than estimated from method 3 due to sire by herd confounding. Predicted sire values were between +400 kg and –400 kg. Rankings of sires with at least 5 progeny were considerably influenced by record classification, especially for sires with highest predicted values. There was less influence on rankings when at least 10 progeny per sire were used while the range in predicted sire values was larger using first lactation records only.

FOOTNOTES

1 This work was part of the Southern Regional Dairy Cattle Breeding Project, S-49, Genetic Methods for Improving Dairy Cattle for the South.

2 National Animal Production Research Institute, P.M.B. 1096, Shika-Zaria, Nigeria.

3 Agricultural Director, Alcan Jamaica Company, Mandeville, Jamaica.






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Copyright © 1986 by the American Dairy Science Association ®.