日粮阴阳离子平衡(DCAB)对热应激肉牛生产性能的影响

摘要

为了研究日粮中不同DCAB对热应激肉牛生产性能、各种生理指标以及外周血淋巴细胞凋亡的影响,选择30头体质量(450±10)kg的西门塔尔牛杂交牛,随机分为3组,每组10头,各组试验日粮分别为I组对照组(DCAB为108 meq· kg 1 DM)、Ⅱ组(228 meq· kg-1 DM)、Ⅲ组(347 meq·kg-1 DM).试验结果表明,日粮中DCAB对热应激肉牛的直肠温度无显著影响,随DCAB的增加线性降低肉牛的呼吸频率(P＜0.05).肉牛日增体质量随DCAB的增加而逐渐增加,其中Ⅱ和Ⅲ组分别比对照组提高29％ (P＜0.05)和25％ (P＜0.05),料重比分别降低了17.34％ (P＜0.05)和11.46％(P＞0.05),日粮NDF和ADF的表观消化率有增加的趋势,Ca、灰分表观消化率呈现二次变化,蛋白质和脂肪的表观消化率无显著变化.与对照组相比,Ⅱ和Ⅲ组血清T4水平分别增加58.1％ (P＜0.05)和31.9％ (P＞0.05),SOD水平分别增加18.98％ (P＞0.05)和48.18％(P＞0.05).日粮中增加DCAB值对血清中血糖、尿素氮、白蛋白等无显著影响.增加DCAB可以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),降低淋巴细胞的比例(P＜0.05),提高肉牛抵抗热应激的能力.综合各项指标,在热应激条件下,日粮中适宜的DCAB值为228 meq·kg-1DM.%The objective of this trial was to study the effects of different DCAB on the production performance, blood chemistry and lymphocyte apoptosis of heat-stressed beef cattle. 30 Simmen-tal cattle with similar weight ( (450±10) kg) were randomly divided into three groups, every group contains ten cattle. The diets of three experimental groups was group I (control group, , DCAB, 108 meq o kg-1 DM) , group Ⅱ (228 meq o kg-1 DM ), group Ⅲ (347 meq o kg-1 DM). The results showed that, under the condition of heat stress, different DCAB value in diet didn't influence rectal temperature, while the respiratory rate decreased linearly with increasing DCAB (P＜0. 05) . Compared with control group, daily weight gain of beef cattle in group Ⅱ and Ⅲ increased 29% (P＜0. 05＝ and 25% (P＜0. 05＝, respectively, feed conversion(feed/gain)decreased by 17. 34% (P＜0. 05＝ and 11.46% (P＞0. 05), respectively. With the increasing DCAB, dietary NDF and ADF apparent digestibility improved (P＞0. 05), Ca, ash apparent digestibility showed quadratic change, crude protein and crude fat apparent digestibility had no significant difference. Compared with the control group, serum T4 levels of group Ⅱ and group Ⅲ were increased 58. 1% (P＜0. 05＝ and 31. 9% (P＞0. 05), respectively, SOD levels increased 18. 98% (P＞0. 05) and 48. 18% (P＞0. 05 ), respectively. Increasing DCAB had no significant effect on serum glucose and urea nitrogen, albumin. Increased DCAB could significantly reduce lymphocytes early apoptosis (P＜0. 01＝ , late apoptosis (P＜0. 01＝ and total apoptosis rate (P＜0. 01＝ , reduce the proportion of lymphocytes (P＜0. 05＝ in peripheral blood of beef cattle, and improve the ability to resist heat stress. In conclusion, the suitable level of DCAB was 228 meq o kg-1 DM in diet of heat-stressed beef cattle.