The Exploration Of Models And Limiting Sequence Of Essential Amino Acids In Lambs

This research was conducted to investigate the effect of lysine(Lys),methionine(Met),threonine(Thr)and tryptophan(Trp)deducted in diet on the growth performance,slaughter performance,digestion and metabolism,and serum biochemical parameters in Hu lambs,identify and establish limiting sequence and balanced model by using indexes of average daily gain(ADG),feed/gain(F/G),dressing percentage(DP)and nitrogen retentation(NR)of Hu lambs,and explore the absence of 4 kinds of amino acids and their profile in different parts of lambs’ body in different ages by using carcass method and provide theoretical basis for the large scale farming.This study included three experiments which were described as follows:Experiment 1:The Exploration of growth performance,slaughter performance,models and limiting sequence of four kinds of essential amino acids in weaned lambsThis experiment was conducted to investigate the requirement models and sequence of 4 kinds of essential amino acids in weaned lambs by partial deduction method.One hundred Hu lambs weaned at 50 days of age were randomly divided into five groups Each groups had four replicates.and every replicate had five lambs.The control group(PC)was fed starter with balanced amino acid(Lys、Met、Thr and Trp content: 1.16%、0.38%、0.58% and 0.16%),while 4 experimental groups(PD-Lys,PD-Met,PD-Thr and PD-Trp group)were fed the starter deducted lysine,methionine,threonine and tryptophan based on control group,respectively.The pretest lasted for 10 days,and the formal trial period lasted for 60 days.All the lambs were weighed at 60,90 and 120 days of age,and six lambs selected from each group were slaughtered at 120 days of age.The results showed as follows: 1)Weight in PD-Met groups were lower(P<0.05)than those in PC,PD-Lys,PD-Thr and PD-Trp groups from 120 days of age,average daily gain(ADG)and F/G in PD-Met groups were significantly lower(P<0.05)than those in PC,PD-Lys,PD-Thr and PD-Trp groups from 60 to 90 days of age and 90 to 120 days of age;PD-Met group had lower(P<0.05)empty body weight,carcass,head and feed weight,skin and wool weight,heart weight,liver weight and their percentage of live weight before slaughter compared with PC group).2)According to the ADG and F/G results,the four AAs’ limited sequence of lambs were Met(29)Lys(29)Thr(29)Trp from 60 to 120 days of age.Based on the DP result,the four AAs limiting sequence of lambs were Met(29)Lys(29)Trp(29)Thr at the d 120.According to the ADG and F/G result,the proper model of Lys,Met,Thr and Trp was 100:44:44:8,100:54:45:7 from 60 to 90 days of age and 100:42:38:12,100:47:39:12 from 90 to 120 days of age,repectively.According to the DP result,the proper ratio of 4 AAs was 100: 34: 38: 8 from 60 to 120 days of age.In conclusion,The restriction of Met was greater than Lys,Thr and Trp to lambs.According to the ADG,F/G and DP result,the proper model of Lys,Met,Thr and Trp was 100:44:42:8 and 100:41:38:11 from d 60 to d 90 and 90 to 120 days of age.Experiment 2: Effects of four kinds of essential amino acids on nutrient digestion and metabolism,nitrogen balance model,serum parameters and rumen fermentation of weaned lambsThis experiment investigated the effects of Lys,Met,Thr and Trp in starters on growth performance,nitrogen utilization and serum indices of weaned lambs to determine nitrogen balance limiting sequence and model of amino acids by partial deduction method.The experiment design and method were same as experiment 1.During 80-90 and 110-120 days of age,nitrogen balance test of lambs was determined.During 90 and 120 days of age serum biochemical markers and ruminal fermentation parameter were detected.The results showed as follows: 1)urinary nitrogen emission in PD-Lys and PD-Met groups was significantly higher(P<0.05)than that in PC from 80-90 days of age.Nitrogen deposition,nitrogen apparent digestibility,and nitrogen apparent biological value in PD-Met groups were significantly lower(P<0.05)than that in PC,PD-Thr and PD-Trp groups from 80-90 and 110-120 days of ag.2)According to obtaining the maximum NR,the limiting sequence of four AAs were Met(29)Lys(29)Thr(29)Trp and Met(29)Lys(29)Trp(29)Thr from 60 to 90 days of age and 90 to 120 days of age,and the proper ratio of Lys,Met,Thr and Trp was 100:37:45:12 and 100:41:39:12.3)PD-Met group had lower(P<0.05)glucose concentration at d 90 and serum albumin,globulin,urea nitrogen and cholesterol at d 120 that PC group.4)Rumen p H in PD-Lys and PD-Met groups was significantly lower(P<0.01)than that in PC,PD-Thr and PD-Trp groups.Propionate and butyrate concentration in PD-Met,PD-Thr and PD-Trp groups were significantly lower(P<0.01)than that in PC and PD-Lys groups.In conclusion,the proper model of Lys,Met,Thr and Trp in starter of weaned lambs from 60-120 days of age was 100:39:42:12.The limiting sequence was Met(29)Lys(29)Thr(29)Trp and Met(29)Lys(29)Trp(29)Thr from 60 to 90 days of age and 90 to 120 days of age,respectively.Dietary supplementation of PD-Lys,PD-Met,PD-Thr and PD-Trp in starter could improve nitrogen retention,rumen fermentation function of lambs.Experiment 3: Effects of four kinds of essential amino acid deficiency on meat quality and amino acid content in different parts in weaning Hu lambsThis experiment was conducted to research the effects of lysine,methionine,threonine and tryptophan in starter on meat quality,nutrient content and amino acid content of carcass tissue in weaned Hu lambs.The experiment design and method were same as experiment 1.The results showed as follows: 1)the eye area,p H and flesh color L*in PC and PD-Lys groups were significantly greater than those in PD-Met,PD-Thr and PD-Trp groups(P<0.01),Whereas the shearing force in PD-Lys groups was lower(P<0.05)than that in PD-Thr and PD-Trp groups.2)The carcass crude protein content and the water concentration of head and feet in PD-Met group was significantly lower(P<0.05)than those in PC and PD-Lys groups;the fur crude fat content in PC,PD-Lys and PD-Met groups was lower(P<0.01)than that in PD-Thr and PD-Trp groups;3)The carcasses TEAA and TNAA conent in amino acid unbalanced groups were significantly lower(P<0.05)in PC group.The model of carcass,wool&skin,head and feet in amino acids of Hu lambs from 60-120 days of age were 100:35:44:13,100:21:129:11,100:34:70:7,respectively.Synthesizing the above results,diets deficient in the essential amino acid have great influence on meat quality and the compositions of amino acids of lambs.The model of the essential amino acids of lambs carcass was very close to the model obtained by partial deduction menthod.Above all,the deficiencied and unbalanced essential amino acid directly influenced the weight,average daily gain and slaughter performance,hindered the digestion metabolism of nitrogen,rumen volatile acid,serum biochemical indicators content,reduce meat quality,carcass nutrition,and caused a negative influence on amino acids content and model in different parts of carcasses.moreover,the balanced model got from ADG,F/G,DP and NR approached the proportion of amino acids.