Effects of air temperature, air velocity and feeding level on apparent digestibility, water intake, water loss and growth in calves given a milk substitute diet

Abstract

ABSTRACTSix groups of eight 2-day-old calves were placed successively in a controlled environment chamber. Three groups were exposed to air temperatures of 10° and 25°C. A liquid diet of skimmed-milk substitute and 4 I/day of drinking (free) water was offered to each calf. Within each group, calves were allocated to either a low (<0·2 m/s) or a high (>3 m/s) air velocity and to either a low (30 g dry matter (DM) per kg M0·75per day) or a high (40 g DM per kg M0·75per day) feeding level. At 8 days of age the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·77 (s.e. 0·126) and 0·82 (s.e. 0·126) respectively (P > 0·05). The apparent digestibilities of DM were greater at the low feeding level with low air velocity than for either this feeding level with high air velocity or the high feeding level at both air velocities (P< 0·05) between which there was no significant difference (P > 0·05). At 8 days of age there were significant air temperature × air velocity (P< 001) and air velocity × feeding level interactions in the intake of free water (P< 005). There was a significant air temperature × feeding level interaction for total water intake (P< 0·05). Urinary water loss relative to total water intake was significantly greater at the low air velocity than at the high air velocity (P< 0·05).In a further two groups of eight calves given 30 g DM per kg M 75 per day at 8 days of age, the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·71 (s.e. 0·020) and 0·90 (s.e. 0·013) respectively (P< 0·01). In the same calves given 40 g DM per kg M0·75per day at 20 days of age, the apparent digestibilities of DM at air temperatures of 10° and 25°C were 0·89 (s.e. 0·009) and 0·93 (s.e. 0·011) respectively (P< 0·05). The free and total water intakes, the ratios of (total water intake-faecal water loss): total water intake and the urinary losses of water were significantly greater at the air temperature of 25°C than at 10°C (P< 0·05). Live-weight gains were lower at 10°C than at 25°C (P< 0·01).The results suggested that air temperature, air velocity and feeding level can affect the health and growth of calves less than 4 weeks of age.