LONGEVITY AND LIFETIME PRODUCTIVITY OF COWS IN A PUREBRED HEREFORD AND 2 MULTIBREED SYNTHETIC GROUPS UNDER RANGE CONDITIONS

Records on 983 cows born during a period of 10 yr (1966 to 1975) were used to estimate longevity and lifetime productivity of cows raised under range conditions. The cows were from a purebred Hereford and two multibreed synthetic groups, one composed of beef breeds (Beef Synthetic # 1) and the other composed of two-thirds dairy breeds and one-third beef breeds (Dairy Synthetic). The cows were raised under a stringent culling system in which all heifers were exposed to bulls as yearlings and were expected to wean a calf each year thereafter or they were culled. Cows were also culled for other reasons, such as severe calving problems, bad udders, and leg and feet problems. The mean longevity was 4.2 yr; cows from the synthetic breed groups produced longer (P < .01) than Hereford cows, due to a relatively faster rate of removal at all ages in the purebred Hereford group. The mean values per cow for lifetime productivity traits were 2.7 and 2.5 for number of calves born and weaned and 101.9 kg and 482.9 kg for weight of calf born and weaned, respectively. Male calves were not castrated, and weights of female calves were adjusted to a male basis. Over their lifetimes, Dairy Synthetic cows were more productive, in terms of number and weight of calves born and weaned, than Beef Synthetic #1 cows, which in turn were more productive than purebred Hereford cows (P < .01).