Heat stress affects female Blackbelly ewes during the summer in the tropics

Objective. To determine whether Blackbelly ewes are affected by heat stress (HS) during the summer in a tropical climate. Materials and methods. In this experiment, 21 female ewes were divided into two treatments (T1=7 female lambs and T2=14 multiparous ewes) to evaluate the effect of HS through the temperature and humidity index (THI), physiological, and hematological variables. Results. In the experiment, a THI between 77 and 88 U was found. Likewise, respiratory rate (RR) was higher in T2 in the afternoon (117 bpm) than in the morning (114 bpm) (p<0.05). Also, rectal temperature (RT) was found to be higher in T1 in the afternoon (39.3°C) than in the morning (38.9°C) (p<0.05). Finally, it was found that the heart rate (HR) was higher at T2 during the afternoon (p<0.05). The hematocrit (HCT) and hemoglobin (HB) variables were similar between treatments during the study, but there were differences between samples two to seven (higher concentrations) compared to sample 13 (lowest concentration) (p<0.001). Finally, the potential of the Hydrogen variable (pH) showed variations, being higher in samplings three and six, and lowest values in samples four, five, seven, and twelve (p<0.001). Conclusions. Blackbelly ewes showed severe HS during the summer in the tropics of Guerrero.