日粮中添加金银花黄酮对热应激肉牛肌肉嫩度变化的调控机制

High temperature stress decreased the fleshcolor and the water holding capacity of beef, and dropped meat tenderness. Tenderness is the most important quality indicator of beef meat, and it is closely related with skeletal muscle fible morphosis. It is a key problem that how to regulate meat tenderness and improve meat quality of beef production in summer. Honeysuckle flavones play a role in antioxidation and against oxidative damage on animals.In this project, a heat stress model of beef cattle will be established induced by man-made hot environment,some trials will be conducted to study the change of muscle fible morphology and meat tenderness under heat stress, and discuss the intervene effect of Honeysuckle flavones on muscle tenderness in beef cattle. There are four details. .① A heat stress model of beef cattle was established.② Effect of honeysuckle flavones on muscle tenderization, pH value, the water holding capacity and flesh color in beef cattle under heat stress..③ Effect of honeysuckle flavones on the beef skeletal muscle fible oxidative damage and Ca2+ concentration of beef under heat stress..④ Effect of honeysuckle flavones on beef tenderness and calpain system gene expression under heat stress..This study was investigated with the aim to select the appropriate concentration of honeysuckle flavones and clarity its effect on meat tenderness, and provide scientific basis for future study on regulating the meat tenderization of ruminant.

热应激影响牛肉品质，表现为肉色变白、系水力下降、嫩度差。嫩度是衡量肉品质的重要指标，与肌纤维性质有关。如何调控肌肉嫩度以缓解热应激对肉品质的影响是夏季肉牛生产面临的关键问题。金银花黄酮有抗氧化功能，对应激引起的组织损伤有保护作用。.本项目拟通过人工控温控湿模拟夏季热应激条件，研究日粮中添加不同水平金银花黄酮对由热应激引起的牛肉嫩度变化的调控作用及机制。项目包括以下内容：.①肉牛热应激模型条件的确立及金银花黄酮抗热应激作用；.②金银花黄酮对热应激肉牛背最长肌的嫩度、pH值、系水力等肉质的影响；.③金银花黄酮对由热应激引起的肉牛骨骼肌氧化损伤、肌浆中钙离子浓度异常的干预作用；.④金银花黄酮对热应激肉牛嫩度相关的钙蛋白酶系统表达量及肌原蛋白降解的影响；.通过以上研究，可得到金银花黄酮在肉牛热应激防治中的适宜添加量，阐明其对热应激肉牛嫩度的调控机制，为今后反刍动物肌肉嫩度的营养调控提供理论依据。

南方夏季高温高湿环境可诱发肉牛热应激反应，热应激影响肉牛的产肉性能及肉品质，使牛肉系水力下降，嫩度变差。为了改善夏季热应激条件下肉牛的肌肉嫩度等品质，本项目选用江西省本地黄牛——锦江黄牛为研究对象，研究了在日粮中添加金银花提取物后对热应激肉牛肌肉嫩度的影响及机制。主要内容如下：（1）采取人工控温控湿设置牛舍常温条件，并以夏季高温高湿环境为热应激条件，根据高温条件下牛舍温湿指数、肉牛的生理表现及内分泌激素水平的变化，综合确定热应激模型条件（T:28~33℃,THI>79）；并得出，热应激使宰后牛肉pH值和滴水损失升高，嫩度下降，肉品质变差。（2）在热应激条件确立的基础上，开展了不同水平（0.2%、0.4%和0.6%）的金银花提取物对肉牛的抗热应激作用研究，根据肉牛体温、呼吸频率、皮质醇水平及抗氧化指标的变化，得到在肉牛精料中添加0.2%的金银花提取物对肉牛抗热应激效果最好的结果；而且，0.2%的金银花提取物可使肉牛肌肉嫩度改善，肉色红润，且可提高单不饱和脂肪酸和风味氨基酸水平，改善牛的风味。（3）进一步的研究发现，金银花提取物添加后可提高热应激肉牛的抗氧化功能，并有助于肉牛骨骼肌纤维应激损伤的修复，提高肌肉Ca2+-ATP酶活性。（4）但是，金银花提取物添加后对钙蛋白酶基因mRNA表达及钙蛋白酶的含量无显著影响。通过本项目的研究，本项目得到的结论是：夏季高温高湿环境诱导肉牛出现了热应激反应，在肉牛精料中添加0.2%的金银花提取物可缓解肉牛热应激反应，修复肌纤维的应激损伤，改善牛肉的嫩度及风味；且金银花提取物对热应激肉牛肌肉嫩度的调控机制与其抗氧化功能及对骨骼肌纤维应激损伤的修复有关。该结果对改善牛肉品质，促进南方夏季肉牛养殖业健康稳定发展具有重要意义。