| This paper mainly compared the difference of growth performance,slaughter performance and meat quality between castrated cashmere lambs and female cashmere lambs under the condition of grazing supplementary feeding,to provide a theoretical basis for supplementary feeding scheme and confirmation of nutritional level of cashmere goat.The paper included 4 experiments.The first experiment mainly investigated the differences of herbage intake and percentage of contribution for each forage species between castrated cashmere lambs and female cashmere lambs under the condition of grazing supplementary feeding.Twenty 4-month-old castrated male lambs and twenty 4-month-old female lambs were randomly selected from the Inner Mongolia White Cashmere Goat Breeding Farm.All lambs were grazed on the natural rangeland on the daytime.In addition to grazing,lambs received a measured quantity of corn 300g/lamb(air dry basis)back from the pasture.Fresh water was freely available at all times.Feeding trials were conducted for a period of 97 days,consisting of 7 days for adaptation followed by 90 days of treatment,divided into early period(1-30 d),middle period(31-60d)and late period(61-90 d).The technology of n-alkanes as markers is used to determinate herbage intake and percentage of contribution for each forage species.The second experiment mainly investigated the differences of growth performance,slaughter performance and meat quality between castrated cashmere lambs and female cashmere lambs under the condition of grazing supplementary feeding.At 90 days,six castrated cashmere lambs and six female cashmere lambs were randomly selected and slaughtered by exsanguination,to compare slaughter performance and meat quality.The third experiment mainly investigated the differences of the digestability of nutrients and digestive enzyme activity.Digestability of nutrients(DM,CP,EE,NDF,ADF,Ca and P)were assessed by 4NHCl Acid Insoluble Ash marker in combination with total faecal collection.Activities of amylase,lipase,trypsin and chymotrypsin were measured in duodenum,jejunum,ileum,and pancreas.The last experiment mainly investigated the differences of fatty acids profile in diet,rumen liquid,liver,serum,muscle and fat.The present results showed as followed:(1)Percentage of contribution for each forage species between castrated cashmere lambs and female cashmere lambs was different,although herbage species ingested was same.During 1-30 d,Agriophyllum squarrosum,L.ilicifolius,Allium mongolicum Regel and Setaria viridis were the main forage ingested by castrated cashmere lambs and female cashmere lambs.The three kinds of forage presenting obvious difference was L.ilicifolius,Setaria viridis and Erect Milkvetch between castrated cashmere lambs and female cashmere lambs.Percentage of contribution for the three forage species was 24.65%,14.46% and 4.58% for castrated cashmere lambs,respectively,and 21.09%,18.02% and 7.17% for female cashmere lambs,respectively.During 31-60 d,Artemisia ordosica,Stipa capillata and Allium mongolicum Regel were the main forage ingested by castrated cashmere lambs and female cashmere lambs.Obvious difference was presented in ingested Artemisia ordosica,Stipa capillata,Agriophyllum squarrosum,L.ilicifolius and Setaria viridis between castrated cashmere lambs and female cashmere lambs.Percentage of contribution for the five forage species was 22.40%,22.83%,7.64%,11.08% and 6.96% for castrated cashmere lambs,respectively,and 16.67%,19.31%,13.40%,8.56% and 10.64% for female cashmere lambs,respectively.During 61-90 d,Artemisia ordosica,Agriophyllum squarrosum and L.ilicifolius were the main forage ingested by castrated cashmere lambs and female cashmere lambs.Obvious difference was presented in ingested Artemisia ordosica,L.ilicifolius,Artemisia frigida,Caragana and Scorzonera austriaca between castrated cashmere lambs and female cashmere lambs,and the percentage of contribution for the five forage species was 22.99%,23.49%,3.77%,11.34% and 6.29% for castrated cashmere lambs,respectively,and 17.69%,25.85%,5.49%,9.27% and 8.81% for female cashmere lambs,respectively.(2)Growth performance and organ development of castrated cashmere lambs were better than those of female cashmere lambs.Compared with female cashmere lambs,total weight gain(P=0.029)and ADG(P=0.005)were significantly increased,and DMI tended to increase(P=0.098)in castrated cashmere lambs.Compared with female cashmere lambs,LWBS,head-heel weight,heart weight,omasum weight,and small intestine weight were significantly increased(P<0.05),and carcass weight,skin and wool weight,and stomachus compositus weight tended to increase(P=0.086,P=0.078 and P=0.052,respectively)in castrated cashmere lambs.Female cashmere lambs had a better fat deposition ability,and had more tender and fresher meat.less tail fat weight(P=0.020),less ratio of tail fat weight to carcass weight(P=0.044)and less eye muscle area(P=0.027)than those of castrated cashmere lambs.Castrated cashmere lambs had a decreased tendency in the ratio of mesentery fat weight to carcass weight(P=0.095)as well as GR value(P=0.062)compared to female cashmere lambs.Color grading of meat was significantly decreased(P=0.028),and a* value(P=0.087)as well as shear force(P=0.082)tended to decrease in castrated cashmere lambs compared with female cashmere lambs.(3)During 1-30 d,digestability of nutrients(NDF,ADF and Ca)in castrated cashmere lambs were significantly lower than those in female cashmere lambs(P=0.0002,P=0.007,and P=0.049 respectively),while digestability of P was significantly higher(P=0.070)than that in female cashmere lambs.During 31-60 d,digestability of NDF and P in castrated cashmere lambs were significantly lower than those in female cashmere lambs(P=0.006 and P=0.002,respectively).During 61-90 d,digestability of ADF in castrated cashmere lambs were significantly higher than that in female cashmere lambs(P=0.013).Compared to female lambs,amylase acitvity in jejunum(P=0.022)and pancreas(P=0.115)was increased,while amylase acitvity in ileum was decreased(P=0.0001)in castrated lambs.(4)No significant difference was observed in ingested SFA,PUFA,n-3PUFA and n-6PUFA between castrated lambs and female lambs.Profiles of C24:1,C20:5n3,n-3PUFA,P/S and U/S were markedly higher(P<0.1),while C20:4n6 content was obviously lower in longissimus dorsi muscle of female lambs than those of castrated lambs(P=0.027).There was a increased tendency of C18:0,MUFA and UFA contents in female lambs compared to castrated lambs(P<0.1),while n-6/n-3 was significantly deceased in subcutaneous adipose tissue of female lambs(P=0.044).Contents of C16:0(P=0.029)and C18:0(P=0.073)in the rumen liquid of female lambs were higher than those of castrated lambs,but C18:2t6 content tended to be deceased in female lambs(P=0.074).Profiles of C22:0,C20:5n3,C18:0,C20:0,C20:1,n-3PUFA,and n-3LCPUFA in serum of female lambs were higher than those of castrated lambs(P<0.1).Contents of C20:5n3,n-3LCPUFA,C14:1,C20:1,and C18:2t6 in liver of female lambs were higher than those of castrated lambs(P<0.1),while n-6/n-3 was significantly lower than that of castrated lambs(P= 0.001).In summary,female cashmere lambs have more tender and fresher meat than castrated cashmere lambs under the condition of grazing supplementary feeding,and present more EPA and n-3 PUFA as well as less n-6/n-3,which is benefical to humen health. |
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