Effect Of Different Feeding Standards On Growth,Slaughter Performance,Nutrient Digestion And Utilization Efficiency Of Dorper×Thin-Tailed Han Crossbred Lambs

This study object ensure appropriate feeding standard of Dorper×thin-tailed Han crossbred meat lambs,The experimental diets were formulated according to the following four feeding standards: CARS(China Agriculture Research System based on the study of nutrient requirements of Dorper×thin-tailed Han crossbred sheep),NRC(2007,USA),AFRC(1993,UK)and Feeding Standard of Meat-Producing Sheep and Goats of Chinese agricultural industry standards(NYT,NY/T 816-2004).Dorper×thin-tailed Han crossbred lambs were used as experimental animals and a feeding,slaughter,and metabolism trial were conducted to investigate the effect of different feeding standards on growth performance,slaughter performance,nutrient digestion and utilization efficiency of lambs.Experiment 1 Effects of different feeding standards on growth and slaughter performance of Dorper×thin-tailed Han crossbred meat lambs.Six hundred Dorper×thin-tailed Han crossbred male lambs(28.3±0.86 kg of BW)were randomly assigned into 4 groups with 3 replicates in each group and 50 lambs per replicate according to a single factor experimental design.The experimental diets were formulated according to the following four feeding standards: feeding standard established by our laboratory(Key Laboratory of Feed Biotechnology of the Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences)based on the study of nutrient requirements of Dorper×thin-tailed Han crossbred sheep(abbreviated to ‘CARS’),NRC(2007,USA),AFRC(1993,UK)and Feeding Standard of Meat-Producing Sheep and Goats of Chinese Agricultural Industry Standards(NYT,NY/T 816-2004).The experiment lasted for 81 d,feed intake was recorded every 3 days and lambs were weighed every 20 days.Ten lambs were chosen based on their BW and slaughtered to determine slaughter performance,tissue and organ weight and meat quality when the lambs in CARS group reached 44 kg of BW.The results showed as follows: Actual dry matter intake showed NRC>AFRC>CARS>NYT group,and significant difference was observed between NRC and CARS or NYT groups(P<0.05),but there was no significant difference among the other groups(P>0.05);For average daily gain and carcass weight,CARS>NYT>AFRC group(P>0.05),all of which were significantly higher than that of NRC group(P<0.05);There were significant differences of feed conversion ratio among groups(P<0.05),and CARS<NYT<AFRC<NRC group;For dressing percentage,CARS>NYT>AFRC,and CARS group was significantly higher than NRC group(P<0.05),but no significant differences were found among CARS,AFRC and NYT groups(P>0.05);The percentages of kidneys and liver weight of live weight before slaughter in CARS group were significantly higher than those in the other three groups(P<0.05);Water holding capacity and meat color’s L*,a* and b* values of the longissimus were not significantly different among all groups(P>0.05).In conclusion,the actual average daily gain of Dorper×thin-tailed Han sheep crossbred meat lambs is 200 to 250 g;From weight gain and slaughter performance aspects,the standard of CARS has advantages over foreign feeding standards.Experiment 2 Effects of different feeding standards on nutrient digestion and utilization of Dorper×thin-tailed Han crossbred meat lambs.The experiment material method,animal and diets same as experiment 1.Four lambs in each group were selected for a digestion and metabolism trial after the lambs in CARS group reached 37 kg of average body weight,and the pretrial and trial lasted for 7 and 5 days,respectively.The results showed as follows: Apparent digestibility of dry matter and organic matter,CARS>NYT>AFRC>NRC group,and CARS group was significantly higher than those in AFRC and NRC groups(P<0.05),but no significant differences were found among CARS and NYT groups(P>0.05);For apparent digestibility of acid detergent fiber,CARS>NYT>AFRC>NRC group,and CARS group were significantly higher than that of NRC group(P<0.05),but no significant difference was found among CARS,AFRC and NYT groups(P>0.05);Digestive and metabolizable energy and apparent digestibility of nitrogen,CARS>NYT>AFRC>NRC group,and CARS and NYT groups were significantly higher than that of AFRC and NRC groups(P<0.05),but no significant differences were found among other groups(P>0.05);For apparent digestibility of gross energy,metabolizability of gross energy and absorbed nitrogen,CARS>NYT>NRC>AFRC group,and CARS and NYT groups were significantly higher than AFRC and NRC groups(P<0.05),but no significant differences were found among other groups(P>0.05);For retained nitrogen and utilization efficiency of nitrogen were not significantly different among all groups(P>0.05);For biological value of nitrogen,NRC>AFRC>CARS>NYT group,and NRC group was significantly higher than that in CARS and NYT groups(P<0.05),but no significant difference was found among other groups(P>0.05).From the aspects of nutrient digestion and utilization and energy and nitrogen metabolism of Dorper×thin-tailed Han crossbred meat lambs,the feeding standard proposed by CARS has advantages over foreign feeding standards.