| Various stressors, such as environmental temperature, nutritional changes, pandemics, etc., will affect cattle and breeding bull's productivity. Nowadays, the global climate grows warm, and the temperature increases greatly, especially in summer. These changes decrease the semen quality, so that the frozen-thawed sperm cannot meet the national standards. Many Breeding centers are forced to stop the production for 2-3 months. That is a direct negative impact on the economy of bull's husbandry. A lot of scientific research personnel have already paid attention to the restriction of frozen-thawed sperm production in summer. However, the recent studies are focused on the endocrine system. Due to hormonal changes in the body with a transient, the use of hormone concentration as an indicator of heat stress parameters, is obviously unscientific. In recent years, heat stress proteins (HSPs) have been the key point. The expression of HSP family is affected by many external factors (including high-temperature environmental stimuli), playing a role in regulation and protection. The recent study show that:inducible HSPs have played a very important role in dairy heat stress regulation. HSP70 can be used as an indicator of the thermal stress. Therefore, whether the HSPs have a similar effect comes to the view.In this study, according to the temperature and humidity index (THI), all bulls were classed into four group as the non-heat stress group (spring), mild heat stress group A(early summer), severe heat stress (midsummer) and mild heat stress group B(early autumn) to discuss summer high temperature on semen quality of bulls and the correlation with inducible HSP60, HSP70 and HSP90 expression.Experiment I:The three species of Simmental, Limousin and Yanbian Cattle (each 15) were taken into the experiments. We analyzed the sperm quality and the related acrosome reaction enzyme activity. Statistical software SPSS was used for the data analysis and comparison, including:the difference in the quality of bull semen at different heat stress levels, and the difference in semen quality among different varieties at the same heat stress level. The results show that:1) severe summer heat stress can cause the quality of bull semen decreased significantly. The testing parameters in the non-heat stress and heat stress in all groups have significantly difference (p<0.05). About the sperm acrosome integrity rate, sperm abnormal rate, sperm activity, severe heat stress are the worst group, significantly different from others (p<0.05), the parameters of sperm density in a mild heat stress group is minimum. Among the three species, Yanbian cattles compared to others have the smallest changes.2) Severe heat stress lead bull acrosome reaction enzyme activities disordered, but the data of enzyme activity among different species is also quite different. Three species has the same trends in hyaluronidase (HYD), lactate dehydrogenase (LDH) and acid phosphatase (ACP) of the energy in the lowest value. Acrosin activity of Limousin cattle showed different trends from the other two species.3) Heat stress causes Simmental bull semen quality and acrosome reaction related enzyme activity changes severely. Simmental bull of the three species, the influence of summer heat stress on semen quality is most obvious.Experimentâ…¡:The Simmental bulls were taken to the experiment to study the HSP's effection. Western-blot and RT-PCR was used to detect the expression changes of HSP60, HSP70, HSP90 in their sperm under heat stress. Experimental data were analyzed by SPSS to explore the correlation of expression variety and heat stress sperm quality. The results showed that:1) in all experimental groups, HSP60, HSP70, HSP90 expression could be detested, but different degree of heat stress will lead to their expression on the changes. Among the non-heat stress and all heat stress groups, the expression of HSPs protein and mRNA was significantly different from each other (P <0.05), and still three kinds of HSPs in protein and mRNA expression trends to paralleled, showing the characteristics of their own.These results propose that 1) heat stress led to decreased semen quality and the acrosome reaction-related activity disorder in bulls.2) Heat stress causes Simmental bull semen quality changes greatly not only the decreased sperm quality but also the acrosome reaction-related activity. Among the three species, the semen of Simmental has the most obvious effects of heat stress in summer. The smallest change happened in Yanbian bull, compared with the other two breeds (Simmental and Limousin) and appeared heat resistance significantly. 3)Different levels of heat stimulation (measured with THI)induce HSPs expression differently. HSP70 is a more sensitive indicator. We suggest that the HSP70 could be used as a monitoring indicator of heat stress and the sperm quality decrease in breeding bull. |
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