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Impact of pre- and postnatal heat stress on dairy calf behavior.

B. Dado-Senn




Impact of pre- and postnatal heat stress on dairy calf behavior.
B. Dado-Senn*, K. N. Gingerich, K. C. Horvath, S. L. Field, E. K. Miller-Cushon, J. Laporta. University of Florida Gainesville, FL.

Pre- and post-natal heat stress alters dairy calf thermoregulation and growth, but less is known about behavior. Herein, we characterized feed intake, activity patterns and cognitive function in dairy calves exposed to prenatal and/or postnatal heat stress. Holstein calves (n = 48) born to late-gestation heat-stressed or cooled dams (prenatal HT vs. CL; shade of barn vs. shade, fans, and soakers; ~46 d; THI >78) were exposed to heat stress or cooling postnatally (postnatal HT vs. CL; shade of barn vs. shade and fans; 56 d; THI >68), resulting in 4 treatments: HTHT, HTCL, CLHT, and CLCL; n = 12/treatment. At 2 d of age, calves were allotted 10 L/d of milk replacer (MR) ad libitum via automatic feeders (8 pens, n = 6 calves/pen where n = 3 calves/prenatal treatment/pen). A 1-d stepdown weaning started at 42 d. Intake was analyzed in daily intervals [0000—0700 (INT1), 0700—1300 (INT2), 1300—1900 (INT3), and 1900—2400 h (INT4)], and intake speed and feeder visits were averaged weekly. Calf activity was recorded (d2—56) via electronic leg-based accelerometers. At 35 d, a procedural learning task in a T-maze was used to assess initial and reversal learning (i.e., participation, number of sessions to pass task). Data were analyzed by PROC MIXED in SAS where calf was experimental unit. Postnatal HT calves consumed less MR relative to postnatal CL calves during INT2, and HTHT calves consumed less MR than CLCL calves during INT3 (P < 0.01). Prenatal HT drank MR slower relative to prenatal CL calves at 14 d (P < 0.01). Postnatal HT calves had fewer unrewarded visits (P < 0.01). Prenatal HT calves spent more time standing relative to prenatal CL calves (421 vs 389 � 4 min; P < 0.01). There was a prenatal x postnatal interaction (P ≤ 0.05) whereby CLHT calves had more standing bouts and decreased standing duration relative to other groups. More prenatal HT calves refused to drink MR in the T-maze task compared with prenatal CL calves (71 vs 100% participation; P = 0.04). Of calves that participated, the number of sessions to pass each learning stage did not differ (P ≥ 0.15). Heat stress either pre- or postnatally impacts calf activity and feeding behavior with potential negative implications on welfare.

Keywords: activity, intake.