Study On Metabolic Rule And Requirements Of Energy And Protein In Chinese Holstein Heifers

The experiment was conducted to study the metabolic rule and requirements of the dietaryenergy and protein of Chinese Holstein Heifer with300kg-350kg and220kg-260kg bodyweight, and quantified the dietary energy and protein requirement of heifers at this stage, by thefeeding test, digestion-metabolism experiment and ruminal digestibility mesurement with nylonbag in vivo.Experiment1: The purpose of this experiment was to studied the effects for requirements ofthe dietary energy and protein metabolism for220-260kg Chinese Holstein Heifer with the dietswith different nutrient levels.(Method)217-month-old healthy heifers with similar initial bodyweight (216.37±2.99kg) were divided into3groups (A, B and C) in a randomized experimentdesign. The heifers in group A, B and C were fed diets with the same ratio of concentrate to forageand different protein levels (DM basis). The crude protein content of experiment`s diet weredividedly13.14%、14.11%and15.02%(DM basis). The result showed that ADG of heifers inexperiment groups were841.43g·d-1、915.71g·d-1and956.67g·d-1, separately. The averageapparent digestibilities of dietary DM and OM were72.93%and72.21%. For heifer at this stage,the average apparent digestibilities of dietary NDF and ADF were61.34%and74.41%. Averagedigestibility for GE was79.60%. Average deposition rate for GE and DE were57.51%and83.34%. The digestibility and deposition rate of dietary CP were70.10%and38.66%. Theaverage rumen degradation rate was44.57%.(Conclusion)The estimated requirement of DER,MER, crude protein(CP), Digestible crude protein (RDCP), rumen degraded protein (RDP) andthe small intestine digestible protein (IRDP) of heifers were:DER（MJ/d）=0.66631W0.75+44.38△W；MER（MJ/d）=0.55794W0.75+36.35△W；CP（g·d-1）=5.81W0.75+673.79△W；DCP（g·d-1）=4.09W0.75+473.79△W；RDP（g·d-1）=2.59W0.75+291.14△W；IDCP（g·d-1）=3.72W0.75+431.82△W；MP（g·d-1）=2.25W0.75+259.14△W。（W is BW of heifers, kg;△W is ADG, kg·d-1）Experiment2: The purpose of this experiment was to studied the effects for requirements ofthe dietary energy and protein and various nutrients metabolism for300-350kg Chinese HolsteinHeifer with differents nutrient levels diaty.(Method)2110-month-old healthy heifers with similarinitial body weight (307.67±2.99kg) were divided into3groups (A, B and C) in a randomizedexperiment design. The heifers in group A, B and C were fed diets with the same ratio ofconcentrate to forage and different nutritional levels (DM basis). The DE and crude proteincontent of experiment`s diet were dividedly10.98MJ kg-1and10.06%,11.43MJ kg-1and11.04%,11.90MJ kg-1and12.04%(DM basis).The result showed the ADG of heifers in experiment groups were620.09g·d-1,820.30g·d-1and887.30g·d-1, separately. The average apparentdigestibilities of dietary DM and OM were70.70%and72.51%.The average apparentdigestibilities of dietary NDF and ADF were68.70%and68.29%for heifer at this stage. Averagedigestibility for GE was67.52%, average deposition rate for GE and DE were57.67%and85.35%. The digestibility and deposition rate of dietary CP were69.77%and41.37%, the averagerumen degradation rate was44.57%. The estimated requirement of DER, MER, crudeprotein(CP), Digestible crude protein (RDCP), rumen degraded protein (RDP) and the smallintestine digestible protein (IRDP) of heifers were:DER（MJ·d-1）=0.73014W0.75+44.38△W；MER（MJ·d-1）=0.61690W0.75+39.50△W；CP（g·d-1）=5.62W0.75+595.31△W；DCP（g·d-1）=3.90W0.75+418.04△W；RDP（g·d-1）=2.50W0.75+266.19△W；IDCP（g·d-1）=3.60W0.75+384.94△W(W is BW of heifers, kg;△W is ADG, kg·d-1)...