Effects of calf management and level of feed supplementation on milk yield and calf growth of Zebu and crossbreed cattle in the semi-arid tropics

Abstract

The study was conducted on 45 Zebu and 37 crossbred cows that calved in two seasons, the wet and dry season. All cows were fed 2 kg of concentrate mixture daily for 40 days pre-partum in addition to grazing. At calving, cows and their calves were randomly assigned to one of four groups: (1) HAR ( n=18) cows were fed a high level of concentrate supplement (4 kg/day) and calves were artificially reared; (2) HRC ( n=24) cows were fed a high level of concentrate supplement (4 kg/day) and restricted suckling of calves was practiced; (3) LAR ( n=23) cows were fed a low level of concentrate supplement (2 kg/day) and calves were artificially reared and (4) LRC ( n=17) cows were fed a low level of concentrate supplement (2 kg/day) and restricted suckling of calves was practiced. Calves in all of the groups were weaned at six months of age. Feeding high or low levels of concentrate supplements to cows was continued for 90 days postpartum. Five animals were excluded from the study for various reasons and the results were derived from 77 cows. Two calves died before weaning. Group LAR had the highest frequency (81.8%) of cows with short lactation lengths (<200 days). Daily milk yield, lactation yield and lactation length were significantly affected by the treatments. Cows in group HAR had a mean lactation yield of 2386±141.77 kg, which was significantly higher than for cows in groups HRS (1539±116.42 kg), LAR (1161±120.84 kg) and LRS (778±131.48 kg). Total milk produced (lactation yield+milk suckled by the calf) by HRS cows averaged 2346.7±101.07 kg, and did not differ ( P<0.05) from that of HAR cows, but was significantly higher than for cows in groups LAR and LRS. The interaction, breed×group significantly influenced the daily milk yield and lactation yield. The lactation length of cows in group HRS, of 290.3±11.51 days, was significantly longer than for cows in the other groups, i.e. HAR, LAR and LRS. Cows calving in the wet and dry seasons did not differ in lactation yields, but the lactation length of cows calving in the dry season was significantly longer than for cows calving in the wet season. Crossbred cows had higher daily milk yields and lactation yields than the Zebu cows ( P<0.05), while lactation lengths of the two breeds did not differ significantly. Calf liveweight and average daily gain to three months of age were significantly affected by group. Calves in group HRS had a significantly higher liveweight, of 49.5±1.14 kg at three months of age, and a higher average daily gain, of 334.8±11.06 g, than calves in the other groups. Calves born in the wet season had higher liveweights at three and six months of age than calves born in the dry season. Crossbred calves had significantly higher liveweights at three and six months of age, and higher mean daily weight gain to three months of age and up to weaning age than the Zebu calves. The performance of the cows in the HRS group in terms of total milk production, longer lactation length and the added advantage of the higher growth rate of calves than of those in the HAR, LAR and LRS groups shows that restricted suckling coupled with a high level of feed supplementation is important for high performance in Zebu and crossbred cattle.