Özet:

In this study, non-genetic factors affecting on the birth weight of Holstein Friesian and Brown Swiss calves raised in the Farm of Agricultural College at Atatürk University were investigated, estimates of phenotypic and genetic parameters were made. Birth weights of male and female calves were determined as 38.8 ± 0.32 kg and 36.5 ± 0.34 kg for Brown Swiss, 37.6 ± 0.37 kg and 36.3 ± 0.40 for Holstein Friesian respectively. Effects of sex, year of calving, month of calving and age of dam on the birth weight were found highly significant (P<0.01). It was found that both of breeds demonstrated different reactions to the conditions originated from the year and month of calving. In the other words, it was observed an interaction between genotype and environment regarding with the two factors. Heritability estimates belonging birth weight were found as 0.36 ± 0.131 for Brown Swiss breed and 0.24 ± 0.177 for Holstein Friesian

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