Reproductive Performance of Friesian-Holstein Cows at Sebele Research Station in South Eastern Botswana

Retrospective data from Sebele Dairy Farm were analysed for reproductive performance of Friesian/Holstein cows. Three hundred records from 1989 to 1995 were used. The herd was zero grazed and the data was analysed for age at first calving (AFC), calf birth weights (BW), calving interval (CI), days open (DO), calving rate (CR), reproductive wastage (RW) and calving difficulty (CD); dystocia, after-birth retention and misrepresentation of foetus) and calving weights (CW). The effects of year of calving (YOC) and year of birth (YOB) were tested. The year of calving affected age at first calving (P 70 months) tended (P=0.062) to influence the birth weights of calves. As cows’ age increased, birth weights of their calves decreased. However, age category did not affect (P>0.05) calving interval or days open. Male calves were heavier (P<0.05) at birth than females (38.7±1.3 kg vs. 36.8±0.7 kg). CW was lower for heifers than for cows and represented 84% of the cows’ weights. Heifers had higher (P<0.01) CR than cows (100 vs. 64.9%), however RW was higher (P<0.01) for heifers than cows (25.0 vs. 11.0%). RW was significantly correlated with birth difficulty (r=0.50; P<0.001). It seems that a low temperature-humidity index in the month of conception resulted in higher CR nine months later. It is recommended that when cows are zero grazed, feed quality should be assured by nutrient balancing and should not affect performance between years.