| In present study,the characteristics of nutrient supply and demand of Alpine Merino sheep were explored under grazing and stall-feeding conditions,and built its requirement models of energy and protein,which can fill the blank of nutrition demand in Alpine Merino growing sheep.Six Alpine Merino growing male sheep were selected to study the grazing nutritional characteristics by the methods of total collected feces acid insoluble ash,and twenty-four Alpine Merino growing male and female sheep were also selected to build the requirement models of energy and protein by gradient feeding,digestion and metabolism,and respiration calorimetry trial.The main results were as follows:1.Grazing nutritional monitoring of Alpine Merino growing sheep In the cold and warm season pasture,the daily DM intakes were respective 1.34 kg and 1.19 kg,and the daily ME intakes were respective 7.78 MJ and 9.77 MJ,and the daily CP intakes were 160 g and 140 g for Alpine Merino growing sheep.And more,there was no significant difference between the two seasons(P>0.05).The rumen pH,NH3-N,TVFA,acetic acid,propionic acid,acetic acid/propionic acid ratio of Alpine Merino growing sheep in cold season pasture were 6.71,6.82 mg/100ml,64.91 mmol/L,74.76%,15.00%and 4.99 respectively,and those indexes in warm season pasture were 6.70,10.10 mg/100ml,49.81 mmol/L,72.72%,14.34%and 5.07 respectively.The rumen fulid NH3-N concentrate in cold season pasture(6.82 mg/100ml)was significantly lower than its in warm season pasture(10.10 mg/100ml)(P<0.05),and the propionic acid ratio in cold season pasture(15%)was significantly higher than its in warm season pasture(14.34%)(P<0.05).The digestibility of OM,CP,NDF and ADF were 62.94%,84.95%,60.07%and 64.08%respectively in the cold season pasture,and 61.23%,72.64%,49.21%and 47.80%respectively in the warm season pasture.And those parameters in cold season were significantly higher than in warm season(P<0.05).2.Effects of feeding levels on growth performance,rumen environment parameters and nutrient utilization of Alpine Merino growing sheep The feed to weight gain ratio(FGR)were the lowest for ad libitum male group(AL)group(6.95)and 0.8AL female group(11.70).The feeding level had significant effects on dry matter intake(DMI),DM digestibility(DMD),average daily gain(ADG)and FGR of Alpine Merino growing sheep(P<0.05).Gender and feeding level had significant effects on nutrient intake and digestibility(P<0.05).The digestibility of OM,NDF and ADF in AL male group were 61.58%,47.11%and 31.55%,and those indexes for AL female group were 62.18%,41.34%and 28.75%respectively.The feeding level had a significant effect on the O2 consumption per metabolic body weight(P<0.05).The pH,NH3-N,TVFA and the ratio of acetic to propionic acid(A/P)in AL male group were 6.55,9.44 mg/100mL,44.70 mmol/L and 3.26,respectively,and those indexes in AL female group were 6.62,15.64 mg/100mL,46.23 mmol/L and 3.77 respectively.The digestibility,metabolism and retention rate of GE in AL male group were 55.41%,52.83%and 35.36%respectively,and 60.64%,58.84%and 39.79%in AL female group.The digestibility and retention rate of nitrogen in AL male group were 68.33%and 39.07%respectively,while those were 64.40%and 26.90%respectively in AL female group.The energy and nitrogen intake had significant effects of gender and feeding level(P<0.05),and also,the interaction effects of gender and feeding level were significant on DMI,FGR,rumen NH3-N concentration,A/P,fecal energy and nitrogen retention(P<0.05).3.Prediction models of energy and protein requirements of Alpine Merino growing sheep The requirement prediction models of net energy maintainance(NEm),metabolic energy maintainance(MEm),net energy for maintainance and gain(NEmg),metabolizable energy for maintainance and gain(MEmg)and digestible energy maintainance and gain(DEmg)to Alpine Merino growing male sheep:LgHP[kJ/(kg·W0.75·d)]=0.0005MEI[kJ/(kg·W0.75·d)]+2.3561,(while MEI=0,HP=NEm);RE[MJ/(kg·W0.75·d)]=0.9491MEI[MJ/(kg·W0.75·d)]-0.2831,(while RE=0,MEI=ME.);NEmg[MJ/(kg·W0.75·d)]=0.0173ADG[g/(kg·W0.75·d)]+0.2927;MEmg[MJ/(kg·W0.75·d)]=0.0301ADG[g/(kg·W0.75·d)]+0.5729;DEmg[MJ/(kg·W0.75·d)]=0.0275ADG[g/(kg·W0.75·d)]+0.7553.The requirement prediction models of NEm,MEm,NEmg,MEmg and DEmg to Alpine Merino growing female sheep:LgHP[kJ/(kg·W0.75·d)]=0.0005MEI[kJ/(kg·W0.75·d)]+2.3285,(while MEI=0,HP=NEm);RE[kJ/(kg·W0.75·d)]=0.9423MEI[kJ/(kg·W0.75·d)]-0.2796,(while RE=0,MEI=MEm);NEmg[MJ/(kg·W0.75·d)]=0.0119ADG[g/(kg·W0.75·d)]+0.3687;MEmg[MJ/(kg·W0.75·d)]=0.0252ADG[g/(kg·W0.75·d)]+0.7540;DEmg[MJ/(kg·W0.75·d)]=0.0257ADG[g/(kg·W0.75·d)]+0.8345.The prediction models of net crude protein maintainance(NPm),digestible crude protein for maintainance and gain(DCPmg),and crude protein for maintainance and gain(CPmg)to Alpine Merino growing male sheep:RN[g/(kg·W0.75·d)]=0.5106NI[g/(kg·W0.75·d)]-0.2208(while NI=0,the value of model intercept is net nitrogen maintainance,and then the 6.25 fold value is NPm);CPmg[g/(kg·W0.75·d)]=0.3664ADG[g/(kg·W0.75·d)]+7.7499;DCP.g[g/(kg·W0.75·d)]=0.2329ADG[g/(kg·W0.75·d)]+6.0190.The prediction models of NPm,DCPmg,and CPmg to Alpine Merino growing female sheep:RN[g/(kg·W0.75·d)]=0.3783NI[g/(kg·W0.75·d)]-0.1904(while NI=0,the value of model intercept is net nitrogen maintainance,and then the 6.25 fold value is NPm);CPmg[g/(kg·W0.75·d)]=0.2024ADG[g/(kg·W0.75·d)]+6.5494;DCPmg[g/(kg·W0.75·d)]=0.0945ADG[g/(kg·W0.75·d)]+4.3776.Based on above models,the calculated NEm,MEm,NPm,km for Alpine Merino growing male and female sheep are 0.227MJ/(kg·W0.75·d),0.283 MJ/(kg·W0.75·d),1.38g/(kg·W0.75·d),0.80,and 0.213MJ/(kg·W0.75·d),0.279 MJ/(kg·W0.75·d),1.19 g/(kg·W0.75·d),0.78,respectively.And more,the authors also recommended the production needs of energy and crude protein for Alpine Merino growing sheep as the attached Table 1 and Table 2. |
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