Dado-Senn Bethany, Gingerich Katie N, Horvath Kelsey C, Field Sena L, Marrero Marcela G, Maunsell Fiona, Miller-Cushon Emily K, Laporta Jimena
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison 53706.
Department of Animal Sciences, University of Florida, Gainesville 32608.
JDS Commun. 2021 Nov 25;3(1):38-43. doi: 10.3168/jdsc.2021-0110. eCollection 2022 Jan.
Heat stress has well-known influences on dairy calf physiology, but less is understood about calf behavioral responses to heat stress. Herein, we evaluated milk replacer intake, standing activity, and lying behaviors of calves exposed to prenatal or postnatal heat stress or both. Holstein calves were born to dams experiencing heat stress (HT; shade of a freestall barn) or cooling (CL; shade, fans, and soakers) during late gestation [~44 d before calving, prenatal; mean daily temperature-humidity index (THI) = 78]. They were then subsequently exposed to postnatal heat stress (shade and natural ventilation of an open-sided barn) or cooling (shade of the barn and forced ventilation by fans) from birth to weaning (56 d; mean daily THI = 77; n = 12 per prenatal × postnatal treatment). Heat stress was confirmed by elevated respiration rate and rectal temperature of the prenatal dam and the postnatal calf. Calves were group-housed with automatic milk feeders, from which milk replacer (MR) intake was assessed. Calf behavior was monitored using loggers and video. Postnatal-HT calves tended to consume less MR per hour in the late morning and drank less MR per visit relative to postnatal-CL calves. Postnatal-HT calves spent more time lying laterally and less time lying sternally in a tucked position during overnight hours. Prenatal-HT calves stood longer across the day, particularly overnight, compared with prenatal-CL calves. This study characterized behavioral responses of preweaning dairy calves exposed to chronic heat stress or active cooling during early-life developmental windows.
热应激对犊牛生理机能有着众所周知的影响，但人们对犊牛对热应激的行为反应了解较少。在此，我们评估了暴露于产前或产后热应激或两者兼有的犊牛的代乳粉摄入量、站立活动和躺卧行为。荷斯坦犊牛出生于妊娠后期（产犊前约44天，产前；平均每日温湿度指数（THI）=78）经历热应激（HT；散栏牛舍的阴凉处）或凉爽环境（CL；阴凉处、风扇和喷水器）的母牛。然后，从出生到断奶（56天；平均每日THI=77；每个产前×产后处理组n=12头），它们随后暴露于产后热应激（开放式牛舍的阴凉处和自然通风）或凉爽环境（牛舍的阴凉处和风扇强制通风）中。通过产前母牛和产后犊牛呼吸频率和直肠温度的升高来确认热应激。犊牛成群饲养，配备自动喂奶器，据此评估代乳粉（MR）摄入量。使用记录仪和视频监测犊牛行为。与产后CL组犊牛相比，产后HT组犊牛在上午晚些时候每小时摄入的MR往往较少，每次采食的MR也较少。产后HT组犊牛在夜间侧卧的时间更多，以蜷缩姿势仰卧的时间更少。与产前CL组犊牛相比，产前HT组犊牛全天站立时间更长，尤其是在夜间。本研究描述了在生命早期发育阶段暴露于慢性热应激或主动降温环境下的断奶前犊牛的行为反应。
