Variations in Removal Reasons and Culling Rates with Age for Dairy Females

Abstract

Reason for removal was recorded on 8722 females [cows] removed from 12 institutional herds 1933-1972. Most frequent primary reasons for removal prior to 2 yr of age were disease with a rate of 68% for 0-5 mo., type 49% for 6-15 mo., and reproduction 66% for 16-24 mo. The rate for reproduction declined from peak rate at 16-24 mo. to 32% for cows more than 120 mo. of age. Rate due to production reached a peak of 24% during 37-48 mo., then gradually declined to 8%. Mastitis reached a peak rate of 22-24% during interval 73-108 mo. of age, then declined to 12%. Type accounted for 16-19% of all removals after 1st calving. General health accounted for 6-28% after 108 mo. of age. Culling rates among individuals surviving through birth, 5, 15, 24, 36, 48, 60, 72, 84, 96, 108, and 120 mo. of age but removed before or during next age in listed sequence were 4.9, 2.6, 5.9, 15.3, 17.9, 21.5, 23.1, 24.7, 26.2, 29.9 and 34.5%. Variability of bull progeny increased with age for mastitis and type but declined from 6.0-2.4% for total culling rate. Herd-year variations increased from 5.0-9.0% for the total culling rate. Relative variability of means of herd and bull progenies indicated removal due either to mastitis or disease as mostly involuntary compared with general health or production which was mostly voluntary. Culling rates among younger ages indicated larger variability of bull progeny; culling rates at younger ages will be more useful for bull evaluation than culling rates at older ages or length of herdlife.