Thermoregulatory response of black or red lactating Holstein cows in the hot and cold season in southern Brazil.

Dairy cows in pasture-based systems are more susceptible to heat stress. Holstein cows have the black or red phenotypes, the latter having lower absorbance of solar radiation. Therefore, the study's objective was to evaluate whether cows with red (R) coats are more resistant than black (B) cows to hot weather in a subtropical climate. R and B lactating Holstein cows were evaluated during the cold and hot seasons for internal and surface temperature and sweating rate. In the cold season, body temperature (n = 9/group) did not differ between groups, but the average superficial temperature (n = 13/group) was lower in R cows (B: 30.9 ± 0.3 °C; RW: 29.6 ± 0.3 °C; p = 0.02). In the hot season, under mild to moderate heat stress, mean body temperature (n = 9/group) of R cows was lower (B: 38.75 ± 0.01 °C; R: 38.62 ± 0.1 °C; p=<0.0001), whereas no difference was observed in superficial temperature (n = 17/group). The maximum internal temperature and sweating rate (n = 11/group), measured in the hot season, and the number of evaluations in hyperthermia in both seasons did not differ. Therefore, there were differences in thermoregulation between phenotypes under mild to moderate heat stress conditions. However, considering that only discrete differences were observed, the red and white coat is unlikely to benefit the Holstein cow's welfare under mild to moderate thermal stress.

Local regulation of antral follicle development and ovulation in monovulatory species.

The identification of mutations in the genes encoding bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) associated with phenotypes of sterility or increased ovulation rate in sheep aroused interest in the study of the role of local factors in preantral and antral folliculogenesis in different species. An additive mutation in the BMP15 receptor, BMPR1b, which determines an increase in the ovulatory rate, has been introduced in several sheep breeds to increase the number of lambs born. Although these mutations indicate extremely relevant functions of these factors, the literature data on the regulation of the expression and function of these proteins and their receptors are very controversial, possibly due to differences in experimental models. The present review discusses the published data and preliminary results obtained by our group on the participation of local factors in the selection of the dominant follicle, ovulation, and follicular atresia in cattle, focusing on transforming growth factors beta and their receptors. The study of the expression pattern and the functionality of proteins produced by follicular cells and their receptors will allow increasing the knowledge about this local system, known to be involved in ovarian physiopathology and with the potential to promote contraception or increase the ovulation rate in mammals.