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Journal of Dairy Science Vol. 50 No. 9 1448-1457
© 1967 by American Dairy Science Association ®
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Estimation of Genetic Trends in Dairy Cattle Populations1

E. B. Burnside2 and J. E. Legates

Department of Animal Science, North Carolina State University at Raleigh

ABSTRACT

Usefulness of full sisters and paternal half-sisters to estimate genetic trends was investigated, with 34,380 first lactation Holstein Herd Improvement Registry (HHIR) records reported in 335 herds from 1953 to 1961. Paternal half-sister families comprised one-third and full-sister families one-seventh of the data. All records were analyzed to obtain least-squares constants for year of calving. A weighted regression of these constants on years provided an estimate of the annual trend, genetic plus environmental, (63 ± 11 kg for milk and 0.007 ± 0.001 for per cent fat). Full sisters were analyzed to obtain least-squares year constants adjusted for sire and dam effects and corrected for selection. Weighted regression of these constants on years indicated the environmental trend in the population, and comparison with the genetic plus the environmental trend provided an estimate of annual genetic trend (45 ± 16 kg for milk and 0.018 ± 0.003 for per cent fat). A second estimate of the annual genetic trend (55 ± 26 kg for milk and 0.016 ± 0.005 for per cent fat) was obtained by comparing the over-all trend with one-half the genetic, plus the environmental trend estimated from records of paternal half-sisters adjusted for sire effects.

FOOTNOTES

1 Contribution from North Carolina Agricultural Experiment Station, Raleigh. Published with the approval of the Director as Paper no. 2353 of the Journal Series.

2 Present address: Department of Animal Science, University of Guelph, Guelph, Ontario, Canada.






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Copyright © 1967 by the American Dairy Science Association ®.