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E. K. Miller-Cushon, K. C. Horvath, G. E. Dahl, J. Laporta, 0078 In utero exposure to heat stress during late gestation has prolonged negative effects on activity patterns of dairy calves, Journal of Animal Science, Volume 94, Issue suppl_5, October 2016, Page 36, https://doi.org/10.2527/jam2016-0078
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Abstract
Exposure to heat stress (HS) during the dry period not only negatively affects cow performance, but it also exerts carryover effects on postnatal performance of the calf. The objective of this experiment was to evaluate the health, responsiveness, and activity of heifer calves born to cows exposed to HS (provided only shade, n = 13) or cooling (CL, fans, soakers, and shade, n = 9) environmental conditions during the entire dry period (∼56 d). On the day of calving, calves were fed 3.8 L of maternal (HS or CL) colostrum. Within 2.8 ± 2.6 h of birth, we scored suckling reflex (1–3; 1 = no suckling response, 3 = strong suckling response) and movement (1–3; 1 = not able to stand when prompted, 3 = stands promptly). Calves were housed in individual pens and provided pasteurized milk (6 L/d) and ad libitum access to grain and water, until weaning at 49 d. Activity was assessed during the first week of life (week 1), weaning (week 7), and the first week postweaning (week 8) using electronic data loggers (HOBO Pendant G data Logger, Onset computer corp., Pocasset, MA) attached to the left rear leg of the calf. Heifer health was monitored weekly from birth to weaning (heath score 1–5). Data were analyzed by time period in a general linear mixed model, with day as a repeated measure for activity data. All heifers were healthy through the duration of the experiment. At birth, the suckling reflex (1.8 vs. 2.1; SE = 0.24; P = 0.33) and movement score (2.42 vs. 2.33; SE = 0.18; P = 0.69) were similar for CL and HS calves, respectively. However, CL calves spent more time standing in the first week of life (303.6 vs. 254.3 min/d; SE = 9.6; P < 0.001) as a result of longer standing bouts (14.2 vs. 12.2 min/bout; SE = 0.55; P = 0.006). In weeks 7 and 8, CL calves maintained greater total daily standing time (442.6 vs. 406.8 min/d; SE = 10.7; P < 0.019) and spent more time standing/bout (30.7 vs. 24.3 min/bout; SE = 1.2; P < 0.001). However, CL calves had less frequent standing bouts than HS calves (15.4 vs. 17.7 bouts/d; SE = 0.6; P < 0.01). These results suggest that in utero HS during late gestation can have prolonged negative effects on activity patterns of dairy calves.
