热应激对奶山羊生产性能及瘤胃上皮细胞形态结构的影响

Effect of Heat Stress on Dairy Goat Performance and Rumen Epithelial Cell Morphology

【目的】研究热应激对奶山羊生产性能及瘤胃上皮细胞形态结构的影响,为动物在炎热环境中能够维持正常生理机能以及探索促进动物抗热应激的方法提供理论基础和试验依据。【方法】本项目以泌乳中后期奶山羊为动物模型,采用逐渐加热的方式使奶山羊产生热应激,用温湿指数计算当连续1周早、中、晚THI>72时,动物模型建立;采用动物营养学方法,研究热应激对瘤胃内发酵指标、营养物质消化率、生产性能、瘤胃上皮细胞形态结构和超微结构的影响。【结果】①试验期间试验羊THI主要在72和87之间,处于轻度和高度热应激;②热应激极显著地提高了奶山羊直肠温度和呼吸频率(P<0.01),显著地降低了DM、CP、OM、NDF和ADF消化率(P<0.01),干物质采食量和奶产量(P<0.01),以及乳中乳蛋白和乳脂含量(P<0.05),但对乳糖含量影响不显著(P>0.05);③热应激显著降低了一天中各时间点的pH(P<0.05)、NH3-N浓度(P<0.05)、TVFA浓度(P<0.05);④与对照组相比,在热应激30 d时,发现瘤胃液呈稀粥状,酸臭味较浓,且奶山羊瘤胃黏膜乳头呈现大面积的坏死、脱落;当在热应激45 d时,黏膜乳头坏死、脱落情况更为严重;⑤在热应激30和45 d时,瘤胃背囊和腹囊绒毛长度和宽度分别要短于对照组(P<0.05),且随着热应激时间的延长,瘤胃背囊和腹囊的绒毛长度和宽度缩短的也越短(P<0.05)。【结论】①热应激通过显著提高奶山羊的直肠温度和呼吸频率,显著降低日粮各营养物质消化率、瘤胃液发酵参数等,进而显著降低日粮干物质采食量、乳品质及其生产性能;②热应激通过破坏瘤胃上皮组织结构,致使瘤胃黏膜绒毛大面积萎缩、脱落、甚至坏死,进而导致瘤胃黏膜屏障通透性增加。

[ Objective ] Effect of heat stress on dairy goat production performance and rumen epithelial cell morphology were studied in order to provide a rational and experimental basis for animals in hot environments to maintain normal physiological function and to explore methods of resistance to heat stress. [Method] The animal modes were estabished when temperature and humidity index 〉 72 （THI 〉 72） of early, medium and evening for a week. The effect of heat stress on rumen fermentation pattern, digestion and metabolism of nutritive materials, performance, morphology and structure of rumen epithelial cell were studied with mid- and late-lactation dairy goats by animal nutrition methods in this project. [Result] The results showed that THI of test sheep was between 72 and 87 during the tests, and in the mild and high heat stress, which showed dairy goat in continuous heat stress state during the whole experiment period. Heat stress significantly increased rectal temperature and respiration rate （P〈0.01）, significantly reduced DM, CP, OM, NDF and ADF digestibility （P〈0.01）, dry matter intake and milk yield of dairy goats （P〈0.01）, and significantly reduced dairy goat milk protein and milk fat content （P〈0.05）, but the effect on lactose content was not significant （P〉0.05）. Heat stress significantly decreased pH value, NH3-N concentration and TVFAs concentration （P〈0.05） at each time pointin a day. Compared with the control group, rumen fluid of dairy goat was found gruel shape and strongly sour flavor, and the mmen mucosa nipples showed a wide range of necrotic and fall off when in heat stress for 30 days, and the situations of mucosa papillary necrosis and fall offwere more serious when in heat stress for 45 days. This showed that heat stress caused a certain degree injury to the animal rumen mucosa. In the heat stress for 30 days and 45 days, the length and width of rumen dorsal sac and ventral sacs villus were shorter than that of control group （P〈0.05）, and with the prolonged heat stress, the length and width of rumen dorsal sac and ventral sac villus were shortened more short （P〈0.05）. [Conclusion] Heat stress can significantly improve rectal temperature and respiration rate, significantly reduce dietary nutrient digestibility, mmen fermentation parameters, dry matter intake, milk quality and performance of the dairy goat. Heat stress can damage morphology ofrumen epithelial cell, make the mucosal villi atrophy, shed and even necrosis, which increase permeability of the rumen epithelial cell.