Resumen de Estudio de indicadores fisiológicos como predictores de estrés térmico de vacas lecheras en norte de Portugal
J.O.L. Cerqueira, J.P. Araújo, I. Blanco Penedo, Jesús Cantalapiedra, M. Silvestre, S.R. Silva
We studied the physiological indicators (rectal temperature and respiratory rate) on four farms in Northern Portugal, on 53 animals during the year 2011. There were 48 days with temperatures above 25ºC and THI was over 72 on 51 days of the year. In Summer the animals showed a further 1ºC and 40 movements/minute than the observed in Winter. The correlations between physiological and environmental variables were high (r>0.77). And there was a very important and positive correlation between respiratory rate and rectal temperature (r=0.9), which allows measuring just one of those indicators to evaluate heat stress of the animals. When the THI>78 individual cows showed a milk production less than 1.8 kg/cow/day. Rectal temperature and respiratory rate experienced an increase of 1.3ºC and 37.3 movements/minute respectively, when the THI class goes below 72 to over 78.
