Physiological responses and animal behavior in Bonsmara-Hereford crosses vs. Hereford purebred on environment stress

Abstract

Adaptative traits (rectal temperature-RT, respiratory rate-RR) and grazing behavior (Grazing, Ruminating and Rest time, and Sun or Shade time) of Bonsmara-Hereford crossbred-BH, n = 15, and purebred Hereford-HH, n = 18, yearling heifers, in a grazing system of Uruguay. Environment characterization was made using THI adjusted by radiation and wind speed (no, mild, and severe heat weaves), and the comprehensive climatic index-CCI (no, middle, moderate and severe stress). Adaptative traits were measured twice a day, weekly, in two consecutive days in summer and winter at 08h00 and 16h00. Grazing behavior was observed from 07h00 to 21h00 each 600 s twice in summer. The records were analyzed using a mixed model. Significant effect of genotype was observed in mild heat waves for RR and RT in the afternoon (BH lower than HH). For CCI in a.m., the RR was lower than HH in BH in severe stress, while in p.m., the RR was lower in all of CCI levels. RT in p.m. in moderate and severe was lower in BH than in HH. In winter, no differences were found. In grazing behavior, HH rests longer than BH doe; also, HH spends more time in the shade (34 %) than BH does (22 %). BH genotype showed better thermoregulation and grazing behavior at higher temperatures compared to HH.

Análise de parâmetros fisiológicos e perfil de expressão de genes associados ao estresse térmico e eficiência alimentar em bovinos das raças Nelore e Caracu

“…As diferenças na temperatura interna entre animais taurinos e zebuínos foram relatadas entre animais das raças Sahiwal e Frieswal ; Brahman e Angus (Dikmen et al, 2018); Simmental e Angus e Angus e Nelore (Paim et al, 2018). Enquanto estudos comparando Bosmara e Hereford (Taborda et al, 2018), Tharparkar e Karan Fries (Maibam et al, 2017), Nelore e Angus (Valente et al, 2015) não observaram diferenças na temperatura interna entre os animais. Diante do exposto fica evidente que o estresse térmico é peculiar a cada região, raça e animal estudado.…”