The influence of age at first fertilization on some reproductive and performance traits of Simmental cows in first three lactations

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, 1989), the model with fixed influence of factors on observed traits was applied. Established results have shown that the age of head of cattle at first fertilization had highly significant effect (P<0,01) on the occurrence of deviation from the general average in the first service period and also on the weight of calves at first calving. At the second and third calving, the deviations from the general average in investigated reproductive traits were within the limits of random. 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 (P>0,05).