酵母培养物对热应激奶牛泌乳性能和营养物质表观消化率的影响

Effects of yeast culture on lactation performance and apparent digestibility of nutrients in heat-stressed dairy cows

文章旨在研究炎热夏季条件下日粮中酵母培养物添加水平对荷斯坦奶牛生产性能和营养物质表观消化率的影响。试验选取60头中国荷斯坦奶牛,按照胎次、泌乳天数和产奶量进行区组设计,随机分为3组,每组有20头奶牛。对照组奶牛饲喂基础日粮,试验1组奶牛和试验2组奶牛分别在基础日粮的基础上补充饲喂100 g/d·头和200 g/d·头的酵母培养物。预试期2周,正试期8周。试验期间每天记录产奶量,每周采集奶样测定乳成分,正试期最后3 d进行消化试验,采用酸不溶灰分法测定营养物质表观消化率。试验期间,每天大部分时间牛舍的平均温湿指数大于72,意味着奶牛试验期间遭受不同程度的热应激影响。酵母培养物显著提高热应激泌乳早期奶牛的干物质采食量,以饲喂200 g/d·头的奶牛具有最大干物质采食量(P <0.05)。酵母培养物显著增加遭受热应激的泌乳早期奶牛的产奶量,本试验条件下呈线性增加(P <0.05)。酵母培养物显著提高遭受热应激的泌乳早期奶牛的乳糖率,本试验条件下呈线性增加(P <0.05)。遭受热应激的泌乳早期奶牛补充饲喂酵母培养物对其他乳成分无显著影响(P> 0.05)。酵母培养物显著提高热应激条件下泌乳早期奶牛的干物质、粗蛋白质和中性洗涤纤维的消化率(P <0.05),而对粗脂肪和酸性洗涤纤维的消化率无显著影响(P> 0.05)。因此,酵母培养物饲喂遭受热应激的泌乳早期奶牛可以显著增加其干物质采食量和提高产奶量,并改善营养物质消化率,本试验中以200 g/d·头的饲喂剂量最佳。

The aim of this study was to investigate the effects of yeast culture supplementation on the milk production performance and apparent digestibility of nutrients in Holstein dairy cows in hot summer.A total of 60 Chinese Holstein dairy cows was selected and randomly divided into three groups with 20 cows in each group balanced by parity,days in milk and milk yield.The control group were fed basal diet and the experimental group one and two were fed basal diet supplemented with the yeast cultures of 100 g/d/head and 200 g/d/head respectively.The pre-trial period was 2 weeks and the trial period were 8 weeks.During the experiment,milk yield was recorded every day,and milk samples were collected every week for determination of milk composition.The digestion test was conducted in the last 3d and the apparent digestibility of nutrients was determined by acid insoluble ash method.During most days of the experiment,the average temperature and humidity index in the barn was greater than 72,indicating that the cows suffered from different degrees of heat stress.Yeast culture supplementation significantly increased the dry matter intake of early-lactation cows in heat stress and the maximum dry matter intake was observed in cows fed 200 g/d/head(P<0.05).Yeast culture supplementation significantly increased the milk yield of early-lactation cows subjected to heat stress,which showed a linear increase in this experiment(P<0.05).Yeast culture supplementation significantly increased the milk lactose content of early-lactation cows suffering from heat stress,which presented a linear increase(P<0.05).Yeast culture supplementation had no significant effect on other milk components of early-lactation cows suffering from heat stress(P>0.05).Yeast culture supplementation significantly improved the digestibility of dry matter,crude protein and NDF of early-lactation cows under heat stress(P<0.05),but had no significant effect on the digestibility of crude fat and ADF(P>0.05).In conclusion,yeast culture supplementation in the diet of early-lactation cows suffering from heat stress could significantly increase dry matter intake and milk yield,and improve the digestibility of nutrients.In this study,the optimal dosage was 200 g/d/head.