Oocyte quality and heat shock proteins in oocytes from bovine breeds adapted to the tropics under different conditions of environmental thermal stress.

In order to evaluate the influence of thermal stress on physiological parameters, and the oocyte quality of Girolando (n = 12) and adapted Pantaneira (n = 12) cattle, twelve sessions of ultrasound guided follicular aspiration (OPU) were performed, between January and November 2014 (during dry (May-September) and rainy season (October-April) in Brazil). The recovered cumulus-oocyte complexes (COCs) were selected and classified, according to quality, immediately after OPU. The oocytes were then stored in 3% paraformaldehyd before conducting immunofluorescence analysis under confocal microscopy to identify HSP70 and 90 proteins. Before each OPU session, the rectal temperature (RT) and respiratory frequency (RF) of each animal were measured. The black globe humidity index (BGHI) was calculated on the day of the OPUs and 90 days before each OPU session, and related to the thermal stress of the animals. The quality of oocytes from Girolando cattle, but not Pantaneira, showed a negative relationship with BGHI of 90 days before OPU. RT of both breeds did not exceed normal values for cattle below BGHI 95. BGHI variation on the day of OPU did not affect RF of the adapted Pantaneira breed (p = 0.3221). On the other hand, Girolando cattle showed a positive relationship between RF and BGHI (p = 0.0103). With increasing BGHI, the amount of HSP70 increased in Girolando oocytes, however, decreased in the Pantaneira breed. We have not observed a relationship between HSP 90 and BGHI, however Girolando cattle produced a greater amount of this protein in relation to the Pantaneira breed. In conclusion, higher BGHIs, 90 days before OPU session, negatively affect oocyte quality of Girolando cattle and positively affect oocyte quality of the Pantaneira breed. Higher BGHIs on the day of the OPU session negatively affected the respiratory frequency of the Girolando breed, and lead to a higher recruitment of HSP70 to protect oocyte maturation. The opposite pattern was observed for Pantaneira. In addition, Pantaneira cattle produced twice as much as HSP70 as Girolando cattle, suggesting that a natural higher production of this protein could be involved in the mechanisms of adaptation to heat conditions.

Efeito do estresse térmico calórico agudo e crônico sobre a qualidade oocitária de bovinos de raças adaptadas / Effect of acute and chronic caloric heat stress on oocyte quality of adapted breeds cattle

Nos trópicos, o uso de raças adaptadas tem sido uma estratégia para minimizar o efeito do estresse térmico calórico (ETC). No entanto, faltam informações que quantifiquem o estresse e o seu efeito sobre a reprodução dessas raças. O objetivo deste estudo foi avaliar a qualidade do oócito recuperado e alguns parâmetros fisiológicos indicadores de ETC em bovinos de raças adaptadas. Animais Bos taurus x Bos indicus (n=6) e Bos taurus (raça Pantaneira; n=12), localizados na região de transição entre o Cerrado e o Pantanal brasileiro, foram submetidos à aspiração folicular guiada por ultrassonografia (OPU) em diferentes condições climáticas. Foram realizadas oito sessões de OPU, com intervalo mínimo de sete dias e máximo de 54 dias entre as coletas. Para caracterização climática, foi realizado o cálculo do índice de temperatura e umidade (ITU). Foram quantificados os ITUs do dia da OPU, sete dias antes e 60 dias antes de cada sessão. Os parâmetros fisiológicos e a viabilidade oocitária de fêmeas das raças Girolando e Pantaneira não foram afetados negativamente por ITUs entre 72 e 78. O ETC crônico (60 dias) parece afetar a viabilidade oocitária de doadoras na raça Pantaneira quando ITU é superior a 75.(AU)

In tropical regions, the use of adapted breeds has been a strategy to minimize the effect of heat stress (HS) in cattle. However, information quantifying stress and its effect on reproduction of these breeds is lacking. The aim of this study was to evaluate the quality of the recovered oocyte and some physiological parameters that indicate HS in adapted breed. Bos taurus x Bos indicus (n=6) and Pantaneira (n=12) cows, located in the transition region between Cerrado and Brazilian Pantanal, underwent follicular aspiration guided by ultrasound (OPU) in different weather conditions. Eight sessions of OPU were carried out, with a minimum interval of 7 days and maximum 54 days between sessions. For weather characterization, the temperature and humidity index (THI) was calculated. THI of the day of OPU, 7 days before and 60 days before each session were calculated. The physiological parameters and oocyte viability of Girolando and Pantaneira cows were not negatively influenced under ITU between 72 and 78. The chronic HS (60 days)may affect the oocyte viability of Pantaneira donors when ITU is over 75.(AU)