Adjusting Milk Replacer Intake During Heat Stress and Non-heat Stress as a Means of Improving Dairy Calf Performance

The objective of this study was to evaluate the effects of heat stress and varying levels of milk replacer on dairy calf performance. Holstein bull calves ? 2 d of age were randomly assigned housing, outside under a covered area, heat stress (HS), or inside a controlled environment, non-heat stress (NHS), to test for heat stress effects on growth. Calves were also assigned to one of three feeding strategies: increasing amounts of milk replacer from 1.1% body weight (BW) to 1.5% BW (INC), constant at 1.1% BW (CON), or decreasing from 1.6% BW to 1.2% BW (DEC), adjusted weekly, commencing on day 9 of feeding and ending on day 40. Milk replacer amounts were adjusted twice weekly after weighing. Calves had ad libitum access to commercial starter feed and water. Starter intake, water intake, and fecal score (1 to 4) were recorded daily. Respiration rates and rectal temperatures were recorded twice daily at 0600h and 1800h. Average daily gain was greater (P < 0.01) for NHS (0.79 ? 0.03 kg/d) compared to HS (0.66 ? 0.03 kg/d) The NHS calves consumed more starter (P < 0.01) than HS (1.77 vs 1.16 ? 0.06 kg/d. Water consumption averaged 3923 ? 105 mL/d for HS which was greater (P < 0.01) than NHS (2338 ? 105 mL/d). No significant differences were observed among the feeding treatment groups for weight gain (P = 0.73). Milk replacer levels had a significant impact (P < 0.01) on the amount of calf starter consumed with CON consuming the most (1.64 ? 0.07 kg/d), followed by INC (1.44 ? 0.07) and DEC consuming the least (1.34 ? 0.07 kg/d). Water intake was also significantly impacted by milk replacer levels (P < 0.01). Calves in the DEC group consumed the least amount of starter, and consumed more water (3657 ? 129 mL/d) than both INC calves (3119 ? 129 mL/d) and CON calves (2614 ? 129 mL/d). Overall, housing has an impact on growth in neonatal dairy calves; however, milk replacer levels did not impact growth of the calves.