饲粮添加脂肪酸钙对热应激肉牛生长性能和外周血淋巴细胞凋亡的影响

Dietary Fatty Acid Calcium Affects Growth Performance and Apoptosis of Peripheral Blood Lymphocytes of Heat-Stressed Beef Cattle

本试验旨在研究饲粮添加不同水平脂肪酸钙对热应激肉牛生长性能、生理指标及外周血淋巴细胞凋亡的影响。试验选择30头体重相近[(450±10)kg]的西门塔尔杂交牛随机分为3组,每组10头,对照组(Ⅰ组)饲喂基础饲粮,Ⅱ组和Ⅲ组分别在每头牛每天的基础饲粮中添加100和200 g脂肪酸钙,试验期39 d。结果表明,饲粮中添加脂肪酸钙对热应激肉牛的直肠温度和呼吸频率无显著影响(P>0.05)。与对照组相比,Ⅱ组和Ⅲ组的平均日增重分别提高了37.5%(P<0.05)和20.8%(P>0.05),料重比分别降低了24.38%(P<0.05)和15.79%(P>0.05)。肉牛饲粮中中性洗涤纤维、酸性洗涤纤维和钙的表观消化率随脂肪酸钙添加量的增加而增加(P>0.05),磷的表观消化率随脂肪酸钙添加量的增加呈现先升高后降低的趋势(P>0.05),饲粮中添加脂肪酸钙对粗蛋白质、粗脂肪的表观消化率无显著影响(P>0.05)。肉牛血清中三碘甲腺原氨酸(T3)和甲状腺素(T4)的浓度随着脂肪酸钙添加量的增加呈现为先升高后降低的趋势(P>0.05),其中Ⅱ组血清T3浓度与对照组相比提高了27.73%(P>0.05),Ⅲ组血清T3浓度与对照组相比降低了4.5%(P>0.05)。肉牛血清中皮质醇的浓度随着脂肪酸钙添加量的增加而极显著升高(P<0.01)。饲粮中添加脂肪酸钙对肉牛血清中葡萄糖、尿素氮、总蛋白含量以及超氧化物歧化酶活性无显著影响(P>0.05),Ⅲ组丙二醛含量极显著高于对照组(P<0.01)。200 g脂肪酸钙添加量可以极显著降低热应激肉牛外周血淋巴细胞早期凋亡率(P<0.01)、晚期凋亡率(P<0.01)和总凋亡率(P<0.01),但对外周血淋巴细胞周期和淋巴细胞比例(P>0.05)无明显影响。综合各项指标,在热应激条件下,肉牛饲粮中适宜的脂肪酸钙的添加水平为每天每头100 g。

The objective of this trial was to study the effects of different dietary fatty acid calcium levels on the growth performance,physiological indicators and apoptosis of peripheral blood lymphocytes of heat-stressed beef cattle.Thirty Simmental crossbred cattle with similar body weight of(450±10) kg were randomly divided into three groups,and every group contains ten cattle.The three experimental groups were group Ⅰ(control group,fed basal diet),group Ⅱ [fed basal diet + 100 g fatty acid calcium(a cattle per day)],and group Ⅲ[fed basal diet + 200 g fatty acid calcium(a cattle per day)],respectively.The experiment lasted for 39 d.The results showed that in the condition of heat stress,dietary fatty acid calcium did not significantly influence rectal temperature and respiratory rate(P<0.05).Compared with the control group,average daily gain of beef cattle in groups Ⅱ and Ⅲ were increased by 37.5%(P<0.05) and 20.8%(P>0.05),and feed/gain were decreased by 24.38 %(P<0.05) and 15.79%(P>0.05),respectively.With the increasing dose of fatty acid calcium in diet,the apparent digestibilities of dietary neutral detergent fiber,acid detergent fiber and calcium were improved(P>0.05),phosphorus apparent digestibility was firstly increased and then decreased with the dietary fatty acid calcium increasing(P<0.05),and the apparent digestibilities of crude protein and crude fat were not significantly affected(P>0.05).With the dietary fatty acid calcium increasing,the serum concentrations of T3 and T4 of beef cattle were firstly increased and then decreased(P>0.05).Compared with the control group,serum T3 concentration of beef cattle in group Ⅱ was increased by 27.73%(P>0.05) and in group Ⅲ was decreased by 4.5%(P>0.05).Serum cortisol concentration was increased linearly with the increasing of dietary fatty acid calcium level(P<0.01).Dietary fatty acid calcium had no significant effects on contents of serum glucose,urea nitrogen,total protein and superoxide dismutase activity(P>0.05),but malondialdehyde content in group Ⅱ was significantly higher than that in control group(P<0.01).Dietary fatty acid calcium(200 g) could significantly reduce the early apoptosis rate(P<0.01),late apoptosis rate(P<0.01) and total apoptosis rate(P<0.01) of peripheral blood lymphocytes of beef cattle,but neither proportion of lymphocytes(P>0.05) nor cycle of peripheral blood lymphocytes was affected by supplemental fatty acid calcium.In conclusion,the optimal level of fatty acid calcium is 100 g per head per day for heat-stressed beef cattle.