Effect Of Energy Level Of Concentrate On The Growth Performance And Nutrient Apparent Digestibility In Barn-feeding Early-weaned Yak Calf

This experiment was conducted to investigate the effect of energy level of concentrate on the growth performance, blood biochemical parameters and nutrient digestibility in barn-feeding early-weaned yak calf through two trials, determined suitable energy level to promote growth and development of barn-feeding early-weaned yak calf, and to provide basis data for the scientific breeding of early-weaned yak calf.In experiment1, effect of energy level of concentrate on the growth performance and blood biochemical parameters in barn-feeding early-weaned yak calf.The nutrient level of diets were formulated to meet the recommendation in accordance with Nutrient Requirement of Dairy Cattle calf of National Research Council (2001). The treatments were organized in three levels of net energy for gain(NEg):5.60%6.50and7.40MJ/kg NEg with consistent nitrogen concentration, to investigate energy level of concentrate on the growth performance and blood biochemical parameters in yak calves. Eighteen healthy three-month yak calves with average body weight of56.27±4.7kg were randomly allocated to3groups with3replicates per group and2calves per replicate. The yak calves were randomly subjected to one of the following3treatments:5.60,6.50and7.40MJ/kg NEg. Pre-feeding7days and formal28days. Calves were fed with prairie grass which main ingredient were fescue and chinensis. The results showed that:1. Throughout the feeding period, total dry matter intake of yak calf in6.50and7.40MJ/kg groups were significantly higher than that in5.60MJ/kg group (P<0.05). Crude protein, organic matter, neutral detergent fiber, acid detergent fiber, gross energy, calcium and phosphorus intake in6.50,7.40MJ/kg groups were significantly higher than that in5.60MJ/kg group (P<0.05). There were no significant on ether extract intake among different energy level (P>0.05).2. Average daily gain in6.50MJ/kg group increased by108.00%compared with5.60MJ/kg group (P<0.05), and by25.00%compared with7.40MJ/kg group (P>0.05).Dry grass intake of yak calf in6.50,7.40MJ/kg groups were significantly higher than that in5.60MJ/kg group (P<0.05). Feed/gain in6.50,7.40MJ/kg groups were significantly lower than that in5.60MJ/kg group (P<0.05).3. In trial period, the amount of body length, body height, bust and chest deep on barn-feeding yak calf in6.50MJ/kg group were increased2.83,3.00,2.41,2.50cm respectively, were increased by61.70%,71.42%,60.67%,77.31%compared with5.60MJ/kg group (P<0.05), and were no significant than that in7.40MJ/kg group(P>0.05). There were no significant in pipe circumference among different energy level (P>0.05).4. There were no significant on concentration of serum total protein, albumin and blood urea nitrogen among three groups at the28th day of trial (P>0.05), yak calf in5.60MJ/kg group appeared to have the lowest albumin/globulin, were significantly lower than that in7.40MJ/kg group (P<0.05).Concentration of serum glucose, triglyceride in6.50MJ/kg group were significantly higher than that in5.60MJ/kg group (P<0.05), and were no significant than that in7.40MJ/kg group (P>0.05). All calves had similar content of lactate dehydrogenase and alkaline phosphatase (P>0.05). At the28th day of experiment, the yak calves on concentration of albumin^blood urea nitrogen and non-esterified fatty acids were decreased compared with the1st day of the experiment(P>0.05), and the concentration of serum glucose was increased(P>0.05).5. Although the concentration of serum endocrine hormones, such as insulin, leptin and insulin-like growth factor-1level, was decreased at the final of trial (P>0.05), there were no significant on concentration of serum endocrine hormones among different energy level (P>0.05).6. Considering the growth performance, the suitable energy level for concentration was NEg=6.50MJ/kg. In experiment2, effect of energy level of concentrate on nutrient apparent digestibility in barn-feeding early-weaned yak calf.The selection and feeding of test animal were the same as experiment1. Four yak calves with similar body weight in each group were selected to carry out digestion experiments by collected all calves total feces. The results showed that:1. Dry matter, acid detergent fiber and neutral detergent fiber apparent digestibility of yak calf in6.50MJ/kg were significantly higher than that in5.60and7.40MJ/kg groups (P<0.01). Among three groups, yak calf in6.50MJ/kg group appeared to have the highest organic matter apparent digestibility, increased by5.29%compared with5.60MJ/kg groupt(P<0.01), and by2.25%compared with7.40MJ/kg group(P>0.05). There were no significant on crude protein apparent digestibility with the elevated of energy level (P>0.05).2. Yak calf in6.50MJ/kg group appeared to have the highest gross energy apparent digestibility among three groups, were significantly higher than that in5.60MJ/kg group (P<0.05), and were no significant than that in7.40MJ/kg group (P>0.05).3. Calcium and Phosphorus apparent digestibility tended to decrease with the elevated of energy level(Ca:P=0.06, P:P=0.10).In conclusion, yak could be weaned at3-month-old for stabling breeding. Increase of energy level of concentration could improve dry grass and nutrients intake, dry matter, organic matter and energy digestibility, as well as the glucose and lipid metabolism of barn-feeding yak calf, and finally significantly improved the growth performance and body development. The suitable energy level for concentration was NEg=6.50MJ/kg.