The effect of a split feeding regimen and breed on body temperature of hair sheep ewes in the tropics1

Lactating St. Croix White and Dorper × St. Croix White ewes were used to evaluate the effect of breed and feeding a split ration on body temperature during the cool (March–April) and warm (July–August) seasons in the U.S. Virgin Islands. Within each season ewes were assigned to treatments (n = 8/treatment) based on breed, age, and number of lambs. Treatments consisted of individually feeding ewes daily 0.9 kg concentrate (16.4% CP and 68% TDN) in the morning (AM) or afternoon (PM), 0.45 kg in the morning and afternoon (AM-PM), or no feed (Control) for 56 d beginning on d 7 (lambing = d 0). Ewes were fitted with intravaginal temperature data loggers, set to record vaginal temperature (VT) at 5-min intervals, for 48 h in wk 2 (d 8–14), 5 (d 29–35), and 8 (d 50–56) postpartum. Repeated measures analysis of VT was conducted using a model including treatment, season, and breed as fixed effects. There was no effect of season so data were pooled across season. The interaction of breed with treatment or season was not significant so breed comparisons were made using data pooled across treatments and season. The mean temperature, relative humidity, and temperature–humidity index during the cool and warm seasons were 25.8°C, 85.9%, and 76.1 and 28.3°C, 86.7%, and 80.6, respectively. There was no effect of season or the breed × treatment × season interaction on VT (P > 0.10) so all data were pooled across season and breed for analysis of the treatment effect. During wk 2 there was no difference (P > 0.10) in VT among treatment groups. During wk 5 the AM-PM ewes had higher (P < 0.01) VT than AM, PM, or Control ewes. During wk 8 the AMPM and PM ewes had higher VT (P < 0.01) than either the AM or Control ewes. To evaluate breed effect, data were pooled across treatments and seasons and analyzed using breed as the single main effect. Dorper × St. Croix White ewes had higher (P < 0.0001) VT than St. Croix White ewes. The results show that body temperature of ewes can be influenced by time of feeding and breed. The local breed of sheep, St. Croix White, had a lower body temperature than Dorper × St. Croix White sheep. Ewes that were fed in the afternoon for an extended time during the postpartum period developed elevated body temperatures, which could make them more susceptible to heat stress.