Biophysical responses of Santa Inês and crossbred Santa Inês-Dorper (F1) ewes to a hot environment

ABSTRACT

This study aimed to evaluate the biophysical responses of Santa Inês ewes and crossbred Santa Inês-Dorper ewes in a hot environment. Physiological parameters were measured rectal temperature, respiratory rate, coat surface temperature, skin surface temperature, and heart rate. Biophysical parameters were also calculated heat exchanges by cutaneous convection and radiation, as well as heat storage and thermal conduction in fleece. Throughout the collection period, meteorological variables were similarly monitored. The statistical design was completely randomized in a factorial 2 x 2 (two genotypes and two shifts). According to meteorological variables, the afternoon shift introduced itself with greater heat stress compared with the morning shift. The effect of interaction between genotypes and shifts for respiratory rate, rectal temperature, skin surface temperature, and hair coat surface temperature showed that genotypes exhibit different physiological behavior under similar heat stress situations. Heart rate had the effect of two sources of variation. As for the biophysical parameters, radiation and conduction exchanges in fleece presenting with the shift effect. Heat storage was slightly higher in Santa Inês ewes than in their crossbred Santa Inês-Dorper ewes. It was therefore concluded that crossbred ewes use physiological mechanisms more vigorously to perform heat exchanges, similar to Santa Inês ewes, which have become more adapted to a hot environment.