Effects Of Whole Plant Corn Silage Ratio On Production Performance,nutrient Digestion And Metabolism,rumen Development And Blood Indexes Of Crossbred Fatten Lambs

The aim of this study was to explore the effects of the ratio of whole-plant corn silage on production performance,nutrient digestion and metabolism,rumen development,and blood indicators at different stages of crossbred fatten lambs,and to provide a scientific basis for the popularization and utilization of whole-plant corn silage in lamb fattening.Seventy-two female lambs(Dorper sheep×Hu sheep)with good body condition and an approximate weight(16 ± 1.5kg)were selected and randomly divided into 4 groups,each group with 6 replicates,each replicate with 3 lambs.Group I as the control group was fed with peanut vine as the basis of roughage source in diet,Group Ⅱ,Ⅲ and Ⅳ for experimental groups were respectively fed 20%,40% and60% the whole-plant corn silage(dry matter basis)instead of peanut vine in the diet.The experiment lasted for 115 days,of which the pre-test period was 15 days and the formal test period was 100 days,including 90 days for a feeding trial and 10 days for a digestibility trial.The results showed that:(1)Compared with group I,average daily gain in group III increased significantly(P<0.05)during 1 to 30 days,and feed conversion ratio reduced significantly(P<0.05)during 1 to30 days and 1 to 90 days.(2)The addition of the whole-plant corn silage in diet could not considerably affect the slaughter performance of the experimental lambs,the weight of each gastric compartment and its proportion to the pre-slaughter live weight,the conventional nutritional components of the longissimus muscle(P>0.05).The kidney weights of group I were significantly higher than those of group III,IV(P<0.05),the longissimus muscle brightness(L*)value after slaughter 24 h of group III was significantly higher than that of group I and II(P<0.05).(3)The apparent digestibility of DM,GE of group III and IV was markedly higher than group I(P<0.05).The apparent digestibility of OM,the nitrogen of group II,III,and IV were significantly higher than those of group I(P<0.05).The fecal nitrogen and fecal energy excretion of group II,III,IV were considerably lower than group I(P<0.05).Lambs in group IV had significantly higher urinary nitrogen excretion(P<0.05),which resulted in a lower nitrogen retention rate than that of group III(P<0.05).(4)With the increase of proportions of whole-plant corn silage,the acetate,butyrate,acetate/propionate,the number of P.ruminicola,and the activities of pectinase decreased significantly in rumen fluid of lambs(P<0.05);Group IV had a substantially higher concentration of NH3-N than group I,II,III did in rumen fluid of lambs(P<0.05);The number of R.albus of group II were significantly higher than those of group I,IV(P<0.05).(5)The addition of whole-plant corn silage in the diet could not markedly affect the physiological indicators of blood(P>0.05).Serum glucose concentration in group III was significantly higher than in group I and II on the 90 th day(P<0.05).Group III had a considerably higher serum T-AOC and lower serum MDA concentration than group I did on the 90 th day(P<0.05);Serum SOD,GSH-Px activities in group IV were significantly higher than those in group I on the 60 th day and 90 th day(P<0.05).Group IV had significantly higher serum Ig A and Ig M concentration(P<0.05)and significantly lower levels of TNF-α than group I did on the 60 th day and 90 th day(P<0.05).In conclusion,forty percentage of whole-plant corn silage in diet could significantly increase the proteolytic bacterium and the pectinase activities,improve the rumen fermentation,increase nutrient digestibility,enhance the antioxidant ability and immunity,and promote the healthy growth of lambs.