Effect of feeding level on milk production, body weight change, feed conversion and postpartum oestrus of crossbred lactating cows in tropical conditions

Abstract

Responses to high (H), medium (M) and low (L) feeding levels on milk yield, reproduction and body weight (BW) were evaluated on 30 multiparous crossbred F1 cows (Holstein Friesian×Vietnamese Local Yellow) in lactation week 9–24, divided into two periods of 8 weeks each. The cows were blocked and randomly divided into five groups with feeding levels of H–H, H–L, L–H, L–L and M–M. The medium level was based on the NRC standard (Nutrient Requirements of Dairy Cattle, National Academy Press Washington, DC, 1988), the high level being 10% above and the low 10% under the standard. The cows were fed a constant amount of grass forage, brewer’s grains and varying amounts of concentrates depending on feeding level, body weight and milk yield of each cow at the start of the experiment. The amount of concentrates to each cow was constant during each 8-week period. Mean daily milk yield was 10.43, 9.81, 9.38, 8.74 and 9.88 kg and body weight changes 29, 12, 14, −3 and 19 kg for H–H, H–L, L–H, L–L and M–M cows, respectively. The milk yield and body weight changes were significantly different between feeding levels ( P<0.05) but no significant effects of feeding level on milk composition were found. A strong tendency ( P=0.09) to prolonged interval to first postpartum oestrus was observed on the low feeding level.