Effects Of Different Feeding Methods On Growth Performance,Serum Biochemical Indices And Rumen Microflora Of Yak Calves

This experiment was conducted to investigate the effects of different feeding methods on growth performance,serum biochemical indices and rumen microflora of 6-monthold weaned yak calves.Thirty healthy yak calves with similar body weight were randomly divided into two groups: feeding group and grazing group,feeding concentrate to forage ratio(65:35).The experiment lasted for 7 months and a 10 d prefeeding period.On the first and last day of the normal feeding period,before morning feeding,fasting weight and soft tape measure body size of yak calves in the two groups were weighed,and total weight gain(TWG)and average daily gain(ADG)were calculated.Three days before the end of the experiment,5 yaks were randomly selected from each of the two treatment groups,and fresh feces of each yak calf were collected and cryopreserved at-20℃ every day.Before morning feeding on the last day of the experiment,fasting venous blood was collected for yak calves,and the upper serum was collected after centrifugation and stored at-20℃.Rumen fluid 150 m L was collected,and p H was measured immediately after filtration with 4 layers of gauze.Fresh feces samples were about 30 g.Rumen fluid and feces samples were loaded into a 15 m L centrifuge tube and stored at-20℃,respectively,to facilitate the determination of ammonia nitrogen(NH3-N),microbial protein(MCP)and volatile fatty acid(VFA)contents.The other part was used to determine rumen fluid,faecal fermentation parameters and microbial diversity.The test results show that:1)Concentrate supplements with high nutrition level and good palatability can accelerate the growth and development of yak calves.The daily nutrients needed by yak calves in grazing group were obtained from herbage,but the required nutrients could not be satisfied,and the growth and development of yak calves in grazing group were significantly slower than that in house feeding group.2)The apparent digestibility of CP,OM,DM and EE in house feeding group was significantly higher than that in grazing group,while the digestibility of NDF and ADF was significantly lower than that in grazing group.House feeding can improve the nutrient digestion and absorption of yak calves3)The contents of TP,ALB and BUN in serum were significantly higher than those in grazing group,indicating that feeding concentrate diet can effectively promote protein synthesis in yak calves;The contents of TG and CHOL were higher than those in grazing group,which might be caused by fat deposition accelerated by concentrate.4)The fattening method can effectively promote rumen and intestinal microbial fermentation,but reduce the diversity and richness of gastrointestinal microflora to a certain extent.In conclusion,for yak calves weaned at the age of 6 months,the fattening method of house feeding can significantly improve the weight gain effect of yak calves.Apparent digestibility,serum and other biochemical indexes in the house feeding group were significantly better than those in the grazing group.The fattening method can effectively promote the fermentation of rumen and intestinal microflora,but reduce the diversity and richness of gastrointestinal microflora to some extent.Therefore,the gastrointestinal microflora of yak calves can be improved by adjusting the composition of diet in further studies.