Study On Energy Metabolic Pattern And Energy Requirement Of Growing Dorper Sheep

A2×3factorial arrangement with3levels of energy (low, middle and high) and2genders of dorper sheep (♂+♀) was used to determine the energy metabolic rules andrequirement of growing dorper sheep. The feeding experiment, digestion and metabolismexperiment, indirect respiration calorimetric experiment and rumen degradation experimentwere conducted to study the energy metabolic rule. Factorial method was adopted to study theenergy for maintenance and energy for growth of growing dorper sheep.At15d after weaning, Fifty-four (27♂+27♀) dorper sheep were randomly allottedbased on sex to3dietary treatments with3replicates of3animals for each. Treatments werelow-, middle-and high-energy groups based on dietary digestible energy levels to determineenergy requirement. There was an adaption period of7d in which the sheep were fed theexperimental diets to adapt to the diets before the60d formal experiment with quantitativefeeding. The results of feeding test showed as follows:(1) There were significant sex×energyinteractions on the average daily weight and gain ratio (P <0.001). Dietary proper digestibleenergy for growing dorper sheep is10.66MJ/kg.(2)The ADG of ram sheep was higher (P <0.05) and the gain ratio was Lower than ewe sheep (P <0.05).(3)The regression analysis waspresent the linear relationship between the body weight and age. The line fitting equationswere predicted respectively as follows:Ram sheep: BW=0.229×t+25.895（R~2=0.970，P=0.001）Ewe sheep: BW=0.176×t+24.988（R~2=0.994，P=0.002）In this equations,“BW” indicated the body weight,“t” indicated the day-old.For the determination of energy metabolic rules, the total fecal collection method wasused. Eighteen (9♂+9♀) dorper sheep were randomly allotted based on sex to3dietarytreatments with3animals for each. The results of digestion and metabolism test showed asfollows:(1)The apparent digestibility of dry matter (DM), organic matter (OM) and crudeprotein of ram sheep were higher than ewe sheep(P <0.05), however, no significantdifference of the digestibility of neutral detergent fiber(NDF) and acid detergent fiber(ADF)were found.(2) The middle energy level improved the apparent digestibility of DM, OM, GE, NDF, ADF, but the high energy level reduced the apparent digestibility and metabolic rate ofgross energy(P>0.05). The energy level had no significant (P>0.05) effects on crudeprotein metabolic rates.(3) The apparent digestibility and metabolic rate of the ram and ewesheep were63.07%,51.80%,61.59%and50.76%, respectively.Indirect respiration calorimetric experiment was conducted at the last three days ofdigestion and metabolism experiment after a10days adaptation period. The results showed asfollows:(1) No significant difference was observed between ram and ewe sheep on heatproduction per BW. The ram have higher protein heat production and lower non-protein heatproduction than ewe.(2) The test also indicated that heat production of middle and highenergy level were higher thanthe low energy level (P＜0.05). All groups had similarprotein heat production.Six ram sheep were selected to install permanent rumen fistula for rumen degradationexperiment with16raw materials. The regression analysis was present the negative linearrelationship between the12hours gross energy degradation rate and NDF content. The linefitting equations were predicted as follows:Y=-0.465x+52.789（R~2=0.863，P <0.001）In this equation,“Y” indicated the gross energy degradation rate,“x” indicated the NDFcontent.According to the results of feeding test, digestion and metabolism experiment, indirectrespiration calorimetric experiment, it was predicted that the energy metabolic parameterswhich include Konstanten of maintenance (Km), Konstanten of growth (Kg), the rate ofmethane energy to gross energy (ECH4/GE), the rate of heat increment to gross energy (HI/GE)of ram and ewe sheep were:0.758,0.798,0.780,0.708,8.36%,8.20%,11.88%,12.36%，respectively.Regression equations of requirements for energy of growing dorper sheep werepredicated respectively as follows:Digestible energy:Ram sheep: DE=36.036BGW+530.855W0.75（R~2=0.541，P=0.024）Ewe sheep: DE=48.624BGW+498.883W0.75（R~2=0.787，P=0.001）Metabolizable energy: Ram sheep: ME=31.338BGW+424.728W0.75（R~2=0.542，P=0.038）Ewe sheep: ME=40.649BGW+406.122W0.75（R~2=0.814，P=0.001）Net energy:Ram sheep: NE=24.440BGW+321.861W0.75（R~2=0.543，P=0.044）Ewe sheep: NE=28.779BGW+324.139W0.75（R~2=0.743，P=0.003）In these equations, DE indicated the digestible energy(kJ/d), ME indicated themetabolizable energy(kJ/d), NE indicated the net energy(kJ/d), BGW indicated theaverage daily gain(g), W0.75was the metabolic weight(kg).