The influence of age at first fertilization on performance traits of sim mental cows

Abstract

Certain reproductive and performance traits of Simmental cows, as well as the demonstration of those traits depending on the effect of age at first fertilization, were investigated. The investigation included 606 cows divided according to age at first fertilization, in 10 groups (one month difference among groups). Statistical analysis of data was done by method of Least squares (LSMLMW, Harvey, 1987), the model with fixed influence of factors on observed traits was applied. In regard to the demonstration of performance traits, the effect of age at first fertilization was most expressive in first lactation. The greatest negative deviation from the general average in milk yield and yield of milk fat, were established in first calving cows which were the youngest at fertilization-calving. The increase of age at first fertilization induced the less negative deviations from the general average. In the second and third lactation, deviation from the general average depending on the age at first fertilization, expressed the same trend, but within the limits of random deviations (PX),05).

Ispitivane su proizvodne osobine krava simentalske rase i njihova ispoljenost u zavisnosti od uzrasta pri prvoj oplodnji. Dobijeni rezultati su pokazali da je uzrast grla pri prvoj oplodnji visoko-značajno (P (lt) 0,01) na proizvodnju mleka i mlečne masti u prvoj laktaciji. U drugoj i trećoj laktaciji ispoljenost proizvodnih osobina nije značajno zavisila od uzrasta pri prvoj oplodnji.