Effect of sward height during lactation on heifer and calf performance

Abstract

The study compared the performance of Hereford x Friesian heifers and their calves managed on a Low (58±0.5 mm sward height) (L) or High (107±1.4 mm sward height) (H) pasture cover from calf birth up to weaning at about 90 days over spring 1997. Milk production was measured at days 29 and 65 of lactation using the weigh-nurse-weigh technique. At day 29 the heifers on L had dropped by 0.20 condition score units compared with those on H which increased (P<0.001) condition score by 0.32 units; however, by the end of the trial there was no difference in score between the two treatment groups. Sward height significantly affected milk production at day 65 (P<0.05), the High treatment group producing 24% more milk than the Low (8.7 vs 7.0 kg/cow,). There was a corresponding difference (P<0.001) between ADG of the calves on the L (0.95 kg/day) and the H (1.24 kg/day) treatments from day 65 till weaning. Sward height had little effect on heifer and calf during early lactation. This suggests that under adverse conditions farmers could restrict lactating heifers for the first 65 days of lactation, when they are at a condition score of 3.0 or better, without adversely affecting dam or calf performance. This has practical implications for the date of calving and for feed planning on farms where beef breeding cows are usually run in conjunction with a ewe flock. Keywords: beef cattle, body condition score, calf growth, lactation, sward height