ABSTRACT
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.
Subject(s)
Body Temperature Regulation , Lactation , Seasons , Animals , Cattle/physiology , Female , Brazil , Heat-Shock Response , Hot Temperature , Body Temperature , Cold Temperature , SweatingABSTRACT
The most used reproduction method in beef cattle in Brazil is natural breeding, which corresponds to 84% of calves born. Breeders adopt the bull:cow ratio of 1:25, which results in a sub utilization of bulls, making natural breeding antieconomic and underestimating the reproductive ability of competent bulls. The bull:cow ratio is determined by several factors, such as climate and nutrition, but the most determining factor is the fertility of the bull, estimated with more precision through breeding soundness examination of bulls. The aim of this study was to develop a simulation model as an aid to choose the best bull:cow ratio according to the combination of the many factors that determine this ratio. It is a conceptual, empiric, static, and determinist model which, through the processing of the input data, simulates the best BCR. Developed on the Vensim PLE 6.1 software, the model describes variables related to bulls and cows. Two equations were generated to predict the mating potential of males. In the same way, according to the reproductive status of females, equations were generated to predict the cyclicity rate of the cows. The sum of these equations originated the one that determines BCR according to the reproductive status of females. This model might serve as a tool to support decisions as to the best BCR and could be used with several combinations of models Ì characteristics.(AU)
O método de reprodução mais utilizado em bovinos de corte no Brasil é a monta natural, que corresponde a 84% dos bezerros nascidos. Os criadores adotam a relação touro:vaca de 1:25, o que resulta em uma subutilização de touros, tornando a reprodução natural antieconômica e subestimando a capacidade reprodutiva de touros competentes. A proporção touro:vaca é determinada por alguns fatores, como clima e nutrição, mas o principal fator determinante é a fertilidade do touro, estimada de forma mais precisa por meio do exame andrológico. O objetivo deste estudo foi construir um modelo de simulação como auxílio para a escolha da melhor relação touro:vaca de acordo com a combinação dos diversos fatores que determinam essa relação. É um modelo conceitual, empírico, estático e determinista que, por meio do processamento dos dados de entrada, simula a melhor relação touro:vaca. O modelo foi desenvolvido no software Vensim PLE 6.1. e descreve variáveis relacionadas a touros e vacas. Duas equações foram geradas para prever o potencial de acasalamento dos machos. Da mesma forma, de acordo com a condição reprodutiva das fêmeas, foram geradas equações para prever a taxa de ciclicidade delas. A soma dessas equações originou o que determina a relação touro:vaca de acordo com a condição reprodutiva das fêmeas. Esse modelo pode servir como um recurso para apoiar a decisão sobre a melhor relação touro:vaca e pode ser usado com várias combinações de características dos modelos.(AU)
Subject(s)
Animals , Male , Female , Cattle , Reproduction , Sexual Behavior, Animal , Breeding , Sex Ratio , Mating Preference, AnimalABSTRACT
Cows experiencing high levels of inflammation and specific metabolic conditions tend to have slower follicular growth and lower serum and follicular concentrations of oestradiol (E2). Paraoxonase1 (PON1) activity decreases during inflammatory processes. Therefore, the aim of this study was to evaluate the association between serum and intrafollicular (FF) PON1 activity and the serum and intrafollicular levels of E2 and progesterone (P4), as well as the mRNA expression of genes related to steroidogenesis, metabolism and inflammation in the first post-partum dominant follicle of Holstein cows. No correlation was found between PON1 activity, the expression of the analysed genes and levels of follicular E2 and P4, except for a negative correlation between serum E2 and follicular PO1 activity. Also, no correlation was found between serum and follicular PON1 during the first post-partum follicular wave.
