Factors affecting the functional length of productive life in Slovak Pinzgau cows

Abstract

A proportional hazard model was used to analyze the impact of the most important factors on the length of productive life in 44 796 Slovak Pinzgau cows. The calculations were carried out with Survival Kit 3.12. The milk production level within a herd was the most important factor. The relation between the milk production level and the culling risk was strongly non-linear. Cows with extremely low milk production (less than 1.5 standard deviations below average) had a 4.8 times higher culling risk than average cows. The culling risk for the highest yielding cows was about one half of the risk of average cows. In the first lactation the culling risk was highest at the beginning and decreased in the course of lactation whereas in subsequent lactations the culling risk was highest at the end of lactation. The risk decreased with parity. The effect of age at first calving did not have a large influence on the length of productive life, although a linear increase in culling risk was observed as the age at first calving increased. Cows from expanding herds were at lower risk to be culled compared to cows in herds of stable and decreasing size.

Keywords

• cattle
• functional traits
• longevity
• survival analysis
• risk ratio