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Growth, rectal temperature, and health of male Holstein calves exposed to heat stress during pre-weaning.

A. B. Montevecchio

Abstract:

263
Growth, rectal temperature, and health of male Holstein calves exposed to heat stress during pre-weaning.
A. B. Montevecchio*1, W. Frota1, V. R. Merenda1, J. G. Martin III2, R. C. Chebel1. 1Department of Large Animal Clinical Sciences & Department of Animal Sciences, University of Florida Gainesville, FL, 2Dairy Design Engineers Gainesville, FL.

Objectives were to determine the effects of heat stress exposure of pre-weaned male Holstein calves on rectal temperature (RT), growth, and health. At birth, calves were paired according to the dam's parity (1st vs ≥2nd) and were assigned randomly to 1 of 3 treatments: 50% of the hutch covered with plywood and outside of the barn (HS = 20), hutch in a barn with no cooling (SH = 21), and hutch in a barn with cooling through forced air (SHF = 19). At birth, calves were weighed and, within 48 h, total protein in serum and failure of passive transfer (<5.5 vs. ≥ 5.5 g/dL) were determined. All calves were weighed (BW) and had the rump (RH) and wither (WH) heights measured at 12, 19, 26, 34, 47, 54, 61, and 71 d of age (weaning). Health was scored in the AM, including RT, every 3.5 � 1.1 d from 2 to 68 d of age. A set of hutches (HS = 16, SH = 8, SHF = 15) was evaluated for air speed and temperature at 1000 and 1600 h and calves in these hutches had RT and respiratory frequency (RF) measured at the same time. Data were analyzed by ANOVA for repeated measures. At birth, treatments did not differ (P > 0.10) regarding BW, RH, WH, failure of passive transfer. The SHF treatment had (P < 0.01) the greatest air velocity (AM: HS = 0.60 � 0.07, SH = 0.41 � 0.09, SHF = 1.41 � 0.09 m/sec; PM: HS = 0.66 � 0.07, SH = 0.50 � 0.10, SHF = 1.38 � 0.10 m/sec) and HS treatment had (P < 0.01) the greatest air temperature (AM: HS = 33.40 � 0.12, SH = 30.17 � 0.19, SHF = 30.25 � 0.16�C; PM: HS = 33.91 � 0.18, SH = 32.74 � 0.27, SHF = 32.61 � 0.24�C). In the AM, SH calves had the greatest RT (HS = 38.66 � 0.04, SH = 38.79 � 0.04, SHF = 38.60 � 0.04�C) but, in the PM, HS calves had the greatest RT (HS = 40.07 � 0.07, SH = 39.05 � 0.10, SHF = 38.97 � 0.09�C). Calves in the HS treatment had the greatest RF (AM: HS = 73.63 � 3.65, SH = 38.44 � 3.05, SHF = 36.66 � 2.58 mov/min; PM: HS = 92.27 � 3.44, SH = 42.22 � 2.56, SHF = 37.29 � 1.95 mov/min). Treatment did not affect BW and average daily gain from 12 d of age to weaning, but HS calves had reduced RH (HS = 94.58 � 0.70, SH = 96.29 � 0.70, SHF = 97.10 � 0.76 cm) and WH (HS = 88.52 � 0.76, SH = 89.88 � 0.76, SHF = 91.39 � 0.83 cm) at weaning. Exposure to HS reduces body measurements of male Holstein calves.

Keywords: heat stress, Holstein, growth.

Biography: Ana Beatriz Montevecchio Bernardino was born in Sao Paulo, Brazil. She got her�degree in Veterinary Medicine at�State University of S�o Paulo, in Botucatu on 2018.�In the beginning of 2019, Ana Beatriz came to USA to do an externship with Dr. Chebel and, currently is pursuing a Master of Science in University of Florida.