Avaliação das características do tegumento e dos índices de tolerância ao calor de ovinos de diferentes grupos genéticos no semiárido brasileiro.

Abstract

The adaptability of Somalis, Morada Nova and ½ Doper + ½ Somalis sheep was evaluated through the study of tegument structures. A total of 30 sheeps were used, 10 Somalis, 10 Morada Nova and 10 ½ Doper + ½ Somalis, being all uncastrated males with 150 days old, average live weight of 21.85 ± 0.80 kg. Submitted to confinement and distributed in individual stalls Of 1m2. Skin samples were collected using a 0.5 mm "punch" in three regions: neck, side and thigh after tricotomy and administration of local anesthetic in the area where they were removed. After the histological processing and preparation of the slides, the epidermis, dermis, hair follicles and sweat glands were analyzed. The heat tolerance index of the animals was estimated by the Baccari Junior and Benezra tests, within three consecutive sunny days, and the physiological parameters were measured: rectal temperature (RT) and respiratory rate (RR). The superficial temperature (ST) was obtained through the thermographic camera fluke ti25, calculating the mean temperature of the trunk, neck and head before and after caloric stress. Black Globe Temperature and Humidity Index (GTUI), heat tolerance index (HTI) and heat tolerance coefficient (HTC) were obtained. There was a significant difference (p <0.05) in the sweat gland size, since the Morada Nova group had a larger size. There was no statistical difference for the number of hair follicles, sweat glands, gland depth, thickness of the epidermis and dermis. There was no difference (P> 0.05) between treatments for HTI and RT. The RR, ST and CTC differed significantly (p <0.05) between environmental conditions. The three genetic groups have characteristics of tegument favorable to the survival and adaptation to the hot climate and the group Morada Nova has larger size of sweat glands. All races are well adapted, but the Morada Nova was more adapted to the environmental conditions of the semiarid.