Themoregulatory responses of adapted hair sheep breed in a semiarid environment

Abstract

The aim of this study was to evaluate the thermoregulatory responses of Morada Nova sheep managed in a semiarid region. This study was carried out in four farms, characterized by extensive managed system. Meteorological variables air temperature (Air To, C), relative humidity (RU,%), and black globe temperature (BGT, oC) were recorded. Furthermore, radiant heat load (RHL, W m-2) was calculated. Physiological traits as rectal temperature (RT, oC), respiratory rate (RR, breath/min.) and surface temperature (ST, °C; neck, flank, and croup were recorded at morning (9:00 a.m.) and afternoon (2:00 a.m.) on approximately 160 Morada Nova ewes in the farms at months of March, June, September, and December. The data were analyzed using month effect (March, June, September and December) and time of day (morning and afternoon). It was observed that the RHL, which march and September presented higher average values. The results shows the relation of RR with RHL, there is a direct relationship of these variables over the months in the morning, that is, in the months of higher RHL, higher RR were recorded. In the afternoon RT was higher in all months studied. The same pattern of behavior was observed in these variables in the two periods of the day, but with different intensities. A direct relationship between ST and RHL was not observed, but in the morning ST values were lower when compared to afternoon values this can be explain by effect of heat accumulated in the body, except in June that ST was higher in the morning, coinciding with lower values of RT and RR during the June at the same time. Animals triggered more intense the thermoregulatory mechanisms in the afternoon period, despite higher RHL values are recorded in the morning period, as the effect of heat accumulated in the body of the animal during the day. However, in March, the animals used more effectively the thermoregulation mechanisms, such as RR, RT and ST simultaneous, as a way to maintain homeothermia in the two periods studied. So it is important to provide environmental protection or shade during critical periods of the day, especially in March in this region, even for locally adapted breeds.