Reasons for dairy cow removal in New Zealand were studied. The frequencies of removal were analysed by age. The incidences of infertility. disease, and mastitis increased with age. The rate of survival decreased with age. from 0.87 for 2 years to 0.58 for 10 years and older. The rates forinvoluntary and voluntary culling increased with age. from 0.07 and 0.05 for 2 years to 0.17 and 0.24 for 10 years and older respectively. The rate of death was not significantly different across ages. A statistical analysis was used to identify characteristics which were important in predicting the rate of survival. death. and involuntary culling. The results indicated that milkfat production. age, and calving date were the most important characteristics for predicting incidence of survival and involuntary culling. whereas incidence of death is best predicted by a mean value. The herdlife for dairy cows was calculated at 5.20 lactations for 1955#x2013;56 and as 4.77 for 1985#x2013;86. a decrease of 0.43 lactations over 30 years.
展开▼
