Heat tolerance of Santa Ines ewes with light and dark colored pelage

Abstract

The heat tolerance index (HTI) of 16 light colored and 15 dark colored pelage of Santa Inês breed was evaluated. This study was carried out on hot days with BGHI greater than 90. In order to calculate HTI (10 – (RT2 - RT1)) rectal temperature (RT) was recorded at 01:00 p.m. (RT1) after two hours of rest in the shade. Later they were exposed to direct sun light for one hour and then they rested one more hour under shade, when the RT2 was recorded at 03:00 p.m. A completely randomized design was used to analyze hair length (HL), coat thickness (CT), skin temperature (TS) and coat temperature (TC). No differences on RT were observed between light colored and dark colored hair coat ewes, but all of them raised their temperatures (P<0.05) after heat stress. No differences on HTI, CT, HL, and TS were observed between groups, but the black colored hair coat ewes had the highest TC (P<0.05). No effect on heat tolerance between dark colored and light colored hair coat Santa Inês breed in heat conditions is observed.