Study On Metabolic Rule And Requiements Of Energy And Protein In Replacement Dairy Cattle

This experience systematically studied energy and protein metabolism rules and requirement factorial models of growing Holstein heifer at age of 5⁷ and 8¹0 month by the feeding test, digestion-metabolism experiment and nylon bag in rumen test. Factorial models of growing Holstein heifer at age of 5⁷ and 8¹0 month were established.Experiment 1: Twenty one replacement Holstein heifers at 5-momth-old were selected to study the energy and protein metabolism rules and requirement. 21 replacement Holstein heifers were assigned into 3 groups （7 cows in per group）.According to the weight and average daily gain,the diet was designed to the same crude protein（CP=16%,DM）,the different DE（DE=12.85,13.25,13.66 MJ/kg,DM）.The results showed that the digest-ibility of DM,OM,NDF,ADF and energy were 64.88%⁶6.62%,67.14%⁶9.02%,53.51%⁵5.66%, 51.35%⁵2.68%, 66.16%⁶8.45%.The metabolizability of gross energy （ME/GE） and digestible energy（ME/DE） were 53.89%⁵5.76%,81.23%⁸1.46%. The digestibility, deposit rate and the rumen degradable rate of dietary protein were seperatelly 70.25%⁷4.53%, 44.67%⁴7.34%, 54.75%⁵9.25%。Experiment 2: Twenty one growing Holstein heifer at 8-momth-old were selected to study the energy and protein metabolism rules and requirement. 21 replacement Holstein heifers were assigned into 3 groups （7 heifers in per group）.According to the weight and ADG,the diet was designed to the same crude protein（CP=14%,DM）,the different DE（DE=11.52,12.00,12.51 MJ/kg,DM）.The results showed that the digestibility of DM, OM, NDF, ADF and energy were 59.22%⁶0.23%, 64.67%⁶5.51%, 58.79%⁶1.68%, 52.23%⁵6.60%, 61.84%⁶3.42%.The metabolizability of gross energy （ME/GE） and digestible energy （ME/DE） were 47.99%⁴9.96%,77.56%⁷8.76%;The digestibility, deposit rate and the rumen degradable rate of protein in the diet were 66.20%⁷1.48%、38.17%⁴1.84%、47.85%⁴9.28%.Energy and protein requirement of growing Holstein heifer were estimated by the factorial models as follows:At age of five to seven month: DER（MJ/d）=0.62546W^0.75+26.25ΔW,MER（MJ/d）=0.62546W^0.75+26.25ΔW,Crude protein（g/d）=5.57W^0.75+512.68ΔW,Digestible crude protein of diets（g/d）=4.00W^0.75+368.34ΔW,Rumen degradable protein（g/d）=3.14W^0.75+288.95ΔW,Small intestine degradable protein（g/d）=3.56W^0.75+327.46ΔW,Deposition protein （g/d）=2.55W^0.75+235.06ΔW.At age of eight to ten month:DER（MJ/d）=0.59441W^0.75+29.90ΔW,MER（MJ/d）=0.49201W^0.75+21.64ΔW,Crude protein（g/d）=4.84W^0.75+566.60ΔW,Digestible crude protein of diets（g/d）=3.37W^0.75+394.29ΔW,Rumen degradable protein（g/d）=2.34W^0.75+274.40ΔW,Small intestine degradable protein（g/d）=3.10W^0.75+362.80ΔW,Deposition protein（g/d）（g/d）=1.95W^0.75+228.28ΔW.Note:W,weight;ΔW,average daily gain,kg/d.