Determination of breeding value and genetic trend of holsteins with the aspect of milk yield in the conditions of Afyon

In the study it was aimed to determine the factors affecting first lactation 305-day milk yield, breeding values and genetic trends in Holsteins maintained at two private farm operations in Afyonkarahisar province.Analysis of variance showed that calving year and days open had significant (P<0,05) effects on 305-day milk yield in first lactation. Heritability of this trait was 0,331 ± 0,137. Genetic trend was estimated by regressing of mean breeding values on birth years of cows. The genetic trend was negative and nonsignificant for 305-day milk yield. This value was found to be -4 kg per year. The estimated breeding values ranged from -1,38 ton to 1,053 ton.As a result, corrections for significant environmental factors are needed in a selection program and there was a potential for improvement of milk yield in the Holstein herds of Afyonkarahisar province.