Differential expression of HSF1 and HSPA6 genes and physiological responses in Angus and Simmental cattle breeds.

The aim of this study was to identify whether more and less adapted Angus and Simmental cattle differed in physiological responses and expression of the heat shock factor 1 (HSF1) and the heat shock 70 kDa protein 6 (HSPA6), when subjected to heat stress. Thirty bulls (n = 15 ANG; n = 15 SIM), extremes "more adapted" and "less adapted" within each breed were selected to the heat tolerance test. They were selected according to an index based on the average of the respiratory rate obtained on two hot summer days from one hundred bulls. Before the heat tolerance test day, animals were taken to a paddock with water, grass and shade until 7 a.m. of the following day for morning measurements. They were kept in the barn without access to water and shade until 1 p.m. for the afternoon measurements. Respiratory rate in the morning (MRR) and afternoon (ARR), hair coat surface temperature in the morning (MST) and afternoon (AST), rectal temperature in the morning (MRT) and afternoon (ART) were measured and blood samples were collected for expression analysis of the HSF1 and HSPA6 genes. The MIXED procedure of SAS was used for all statistical analysis. The more adapted Simmental group had lesser values of MRR (P = 0.023) and MRT (P = 0.095), but there was no difference within Angus breed. The ARR was greater (P = 0.004) in less adapted animals for both breeds. The ART was lower in the Simmental breed (P < 0.001). Less adapted had greater levels of mRNA of HSF1 (P = 0.06) and HSPA6 (P = 0.09). In conclusion, respiratory rate, rectal temperature and expression of the HSF1 and HSPA6 genes can be indicators of thermotolerance in taurine cattle. Both breeds show physiologically similar responses under heat stress conditions.

Correction: Tournaments between markers as a strategy to enhance genomic predictions.

[This corrects the article DOI: 10.1371/journal.pone.0217283.].

Heat tolerance responses in a Bos taurus cattle herd raised in a Brazilian climate.

Knowledge of thermoregulatory responses in taurine cattle contribute to identification of animals most adapted to heat and productive when raised under Brazilian climate. The objectives were to verify the morphological and physiological responses related to adaptation to heat of taurine breeds raised under in Brazilian meteorological conditions in different seasons of the year and day periods, and to detect differences within and between breeds to know breed is most adapted. Measurements were made of 74 young bulls (n = 31 Angus; n = 43 Simmental) for the morphological traits: hair length (HL), number of hairs (NH), and coat thickness (CT); and for the physiological traits: respiratory rate (RR) and hair coat surface temperature (ST). The temperature-humidity index (THI) was calculated. The data were subjected to analyses of variance, cluster analysis, and principal component analysis (PCA). The THI (<74) indicates thermal comfort. In the winter, the HL and CT higher than in the spring season (P < 0.0001) in both breeds. Angus exhibited higher HL and CT (P < 0.0001). Within each breed, the animals differed from one another for HL (P < 0.0005). In the spring, CT was similar between the breeds, differing only in the winter season. Angus had higher values (P < 0.0005) of RR and lower values (P < 0.0001) of ST. Both breeds had higher (P < 0.0001) RR and ST in the afternoon. PCA showed that NH and HL better explained variation in adaptation. In general, the breeds have similar morphological responses in the hottest months, but have different physiological responses; Simmental proves to be more physiologically resistant. The afternoon was more stressful than the morning, even though the animals were in a thermal comfort zone. Measuring traits related to hair coat is sufficient for effective evaluation of adaptation, and the season affects the morphological and physiological traits of taurine cattle raised.