Genetic Components for Milk Production and it is Composition Estimated by Using Sire and Animal Models in A Herd of Friesian Cows

Document Type : Original Article

Authors

1 Animal Production Dept., Fac. of Agriculture, Kafrelsheikh University

2 Animal Production Res. Inst., Ministry of Agric., Dokki, Giza, Egypt

3 Animal Production Dept., Faculty of Agric., Tanta University.

4 Animal Production Dept., Faculty of Agriculture, Mansoura University.

Abstract

A total number of  eighty seventy four Friesian cows which, kept at  Sakha and El–Karda farms, from 1996 to 2002  are used to estimate  heritability (h2) , phenotypic (rp) and genetic correlations (rg) among three months and 305 day milk yield traits by using sire model (SM) and animal model (AM). The SM includes the random effects of bull and cows within bulls and main effects of  herd year season, and lactation number and days open as a regression. The animal model includes the main effects of  herd year season and lactation number and days open as a regression and random effects of animals, permanent and errors.Estimates of h2 of milk   yield traits for sire models  are  moderate and between from  f0.116 to 0.264 as calculated from sire components and from 0.036 to 0.068 from dam components, while the h2  for milk traits from AM ranged from 0.046 to 0.062. Genetic correlations between milk production traits are  positive, high and near similar for  SM and AM and between from 0.88 to 0.99. The high estimates of genetic correlation in the present study offer the possibility to select for yield traits as early ages, .i.e., at 90 days of lactation. Also, this study indicate that, using of SM is useful when a, small number of observations and little pedigree information is available.

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