EFFECTS OF HEAT STRESS ON PHYSIOLOGICAL PARAMETERS AND SERUM CONCENTRATION OF HSP70 IN INDIGENOUS BREEDS OF SHEEP IN NIGERIA

Heat stress is one of the most challenging environmental conditions affecting livestock production especially in the tropical regions of the world. The present study was conducted to examine the physiological response and HSP70 secretion in four extensively managed indigenous sheep breeds with little access to shade. Rectal temperature (RT), Skin temperature (ST), Respiration rate (RR) and Heart rate (HR) were taken from 565 adult rams comprising 139 Uda, 88 Yankassa, 221 Balami and 117 West African Dwarf sheep in early morning and midafternoon at the peak of the dry season in Ibadan, South West Nigeria. Extracellular heat shock protein 70 (HSP70) concentration was determined by ELISA. At Temperature Humidity Index (THI) > 82 significant differences were observed between the early morning and midafternoon readings in ST in all the breeds, in RT for WAD and Yankassa and RR in Uda and WAD. In the pooled readings there was a significant difference (p < 0.05) between Yankassa and other breeds studied in RR. The concentration of HSP70 ranged from 69.17 to 210.71 ng.mL-1 with the highest value recorded for Uda. The investigated breeds differ in their response to heat stress.