Study On Metabolic Rule And Requiements Of Energy And Protein In Replacement Holstein Heifers

This experiment systematically studied requirements and metabolism rules of energyand protein at weight of90～120and140～200kg of Holstein heifers by the feeding test,digestion-metabolism experiment and nylon bag in rumen test, meanwhile it determinedthe basic models of Holstein calves’ nutritional requirement in this experimental condition.Experiment1: This experiment mainly studied requirements of energy and protein andeffects of different energy levels on various nutrients metabolism regulation at weight of90～120kg of Holstein heifers.21healthy Holstein heifers with similar body weight about94.74±1.51kg were randomly divided into3group （7cows in per group）.3groups dietdigestible energy were different （13.90MJ/kg，13.40MJ/kg，12.90MJ/kgDM）, while itsdiets were kept consistent in protein levels （CP=20%DM）. The results showed that theapparent digestibility of DM, OM, NDF and ADF respectively were66.42%～69.02%，64.37%～67.20%，46.81%～54.68%and46.81%～54.17%; The gross energy digestibility,gross energy metabolic rate and digestible energy metabolic rate respectively were64.05%～65.97%，49.98%～51.43%and77.57%～78.03%；The digestibility and depositrate of crude protein, the deposit rate of digestive protein and the rumen degradable raterespectively were70.56%～71.66%，38.57%～40.46%，54.66%～56.46%and52.68%～55.07%。The calculation model of energy and the requirements for total protein at weight of90～120kg of Holstein heifers:DER（MJ/d）=0.65878W^0.75+24.079ΔW；MER（MJ/d）=0.51381W^0.75+18.711ΔW；Crude protein（g/d）=6.34W^0.75+612.74ΔW；Digestible crude protein of diets（g/d）=4.49W^0.75+434.17ΔW；Rumen degradable protein（g/d）=3.41W^0.75+329.59ΔW；Small intestine degradable protein（g/d）=4.05W^0.75+391.69ΔW；Deposition protein （g/d）=2.49W^0.75+241.05ΔW；Note：W, Fasting weight（kg）; ΔW, average daily gain, kg/d.Experiment2: This experiment mainly studied requirements of energy and protein andeffects of different protein levels on various nutrients metabolism regulation at weight of140～200kg of Holstein heifers.21selected and healthy Holstein heifers whose weightare similar about142.58±1.50kg were randomly divided into3group （7cows in per group）. 3groups diet protein levels were different （16.10％，15.10％and14.11％，DM）, while itsdiet were kept consistent in digestible energy levels （12.82MJ/kg，DM）. The resultsshowed that the apparent digestibility of DM, OM, NDF and ADF respectively was59.86%～63.95%，64.14%～68.39%，59.33%～64.72%and60.73%～62.62%；The grossenergy digestibility, gross energy metabolic rate and digestible energy metabolic raterespectively were58.74%～60.60%，46.90%～48.39%and79.83%～80.29%；Thedigestibility，deposit rate of crude protein, the deposit rate of digestive protein and therumen degradable rate respectively were72.53%～74.73%，37.78%～44.80%，50.55%～60.80%and47.31%～47.56%.The calculation model of energy and the requirements for total protein at weight of140～200kg of Holstein heifers:DER（MJ/d）=0.66509W^0.75+36.051ΔW；MER（MJ/d）=0.58785W^0.75+32.042ΔW；Crude protein（g/d）=4.98W^0.75+663.17ΔW；Digestible crude protein of diets（g/d）=3.67W^0.75+488.16ΔW；Rumen degradable protein（g/d）=2.36W^0.75+314.81ΔW；Small intestine degradable protein（g/d）=3.18W^0.75+424.76ΔW；Deposition protein（g/d）=2.05W^0.75+272.88ΔW；Note：W, Fasting weight（kg）; ΔW, average daily gain, kg/d.