First calving performance of beef cattle. 2. A comparison of Shorthorns and dairy crossbreds

Abstract

In each of 4 years, drafts of Shorthorn and Dairy x Shorthorn heifers were run together and fed to grow either slowly or moderately from weaning at 7 months until joining for two months at 15 months of age. Thereafter they grazed together on improved pasture in a 430 mm rainfall Mediterranean environment. Their performance was compared until their second calving and their calves' performances until weaning. Year x breed type interactions were significant for most variables measured. Between their first joining and first calving, the fourth draft of Shorthorn heifers gained 59 kg less liveweight than the crossbreds, but there was little difference in liveweight gain between the breed types in the other three drafts. Survival of the fourth draft of Shorthorn dams and calves was also 32 and 42% lower than of crossbreds. Concurrently, the third draft of Shorthorns lost 21 kg more liveweight than the crossbreds between first calving and their second joining, but performed similarly or better in the other 3 years. The third draft of Shorthorns also had a 63% lower second calving rate than the crossbreds, but the previous drafts had a similar rate of second calving. The average weaning weights of the second and third drafts of Shorthorn calves were 37 and 34 kg lower, respectively, than the crossbred calves, but only 8 and 16 kg lower in the first and fourth drafts, respectively. The third draft of Shorthorn dams were 90 kg lighter at weaning than the crossbreds but the other Shorthorn drafts were only 20 to 29 kg lighter. The intercalving interval of the fourth draft of Shorthorns was 28 days longer than that of the crossbreds, but was similar to or 23 to 30 days shorter for the previous drafts. Superior performance of the crossbreds was most apparent in the year of lowest rainfall and pasture availability, during which the third draft suckled their first calves and were joined for the second time and the fourth draft calved for the first time. First calving dates of dairy crossbreds were 14 days later than those of Shorthorns if grown slowly before joining, but were similar if grown moderately. Crossbred dams suffered 11 and 25% more dystokia at first calving of the first and third drafts and 14% more if grown slowly, but not if grown moderately before their first joining. Birth weights of calves out of crossbred dams were consistently 2 kg higher than those out of Shorthorn dams. First calving rates of the two types of cattle were similar and high (about 90%).