VARIANCE IN HOLSTEIN - FRIESIAN COW LONGEVITY

Tatyana Ivanova

Abstract: The purpose of the current study was to determine the sources of specific variance of cow longevity. The study comprised 1440 cows from the Agricultural Institute farm originated from 119 sires belonging to five lines during the period from 1981 to 2006. Lactations are fixed from Ist to VIIst as if the next lactations are excluded from the analysis because of their small number. The calving seasons for order of lactation in cows are: winter (December - February), spring (March - May), summer (June - August) and autumn (September - November). Cow longevity /from the first calving to the date of culling/ is measured by days. A linear statistical model was used to determine the analysis of variance (Harvey, 1990). The birth year, the order of lactation and the line exercise significant influence on the phenotypic variety of cow longevity (P< 0.001). Best results are obtained in daughters from the bull line P.F.A.Chiff. It is established high significant influence of the regression effects of milk butter, milk protein, age of first calving and milk- yield life with cow longevity (P< 0.001).

Keywords: cow longevity; cows; factors; milk yield

Date published: 2023-02-28