Effects Of Different Level And Source Of Methionine In Growing-finishing Pig Diets On Growth Performance And Meat Quality

Methionine are considered as the second limiting amino acids for pigs,plays a critical role in protein synthesis and metabolism.However,in recent years,there has little study to explore the effect of methionine on growth performance and meat quality of pigs,so the aim of this study is to explore the effect of increasing dietary sulfur amino acids by using DLM or HMTBA on growth performance,carcass characteristics and meat quality in growing-finishing pigs through feeding and slaughter experiment,and the possible mechanisms were discussed through tissue gene expression and blood biochemical index.The pigs were divided into three groups:control(CON),non-sulfur amino acids(SAA)supplementation fed pigs,diets was formulated according to the NRC(2012)recommendations;The DLM and HMTBA diets were formulated by supplementation with DL-Met or HMTBA,respectively,and achieved at 125%the total standard ileal digestible sulfur amino acids(SSAA)present in the control(CON)diet.The experiment was conducted in a randomized complete block design.A total of 144(half gilts and half barrows)crossbred Durocx(Landracex York)piglets(11.16±0.23kg,～5 weeks of age)were divided on the basis of body weight(BW)and sex,into 36 pens(four pigs/pen).Each pen of pigs was fed one of three diets,each diet replicated 6 times by barrow and gilt pens,respectively.This research was divided into five phases accordance with NRC(2012),over 20 weeks period.Pigs were weighted,collected blood and recorded growth performance at the end of each experimental period and one pig with average BW was selected from each pen and slaughtered for carcass and meat quality evaluating after growth experiment come to an end.Muscle,liver and adipose samples were collected for further analyzed.The main results are as fellows:1.Changes in growth performance of finishing pigs:The HMTBA and DLM groups showed higher(P<0.05)G:F than the CON group at the 25-50kg and 50-75kg period,respectively,and there was no difference(P>0.10)in growth performance from total phase.2.Changes in plasma SAA profiles of finishing pigs:The effect of dietary SAA level on SAA metabolism in finishing-pigs showed significant stage characters.Compared with CON groups,dietary DLM or HMTBA supplementation increased(P<0.05)plasma Tau concentration at phase 1(11-25kg)and 3(50-75kg),plasma methionine concentration increased(P<0.05)at phase 2(25-50kg),HMTBA group increased(P<0.05)plasma Cys concentration at phase 4(75-100kg),DLM group decreased plasma Met and Cys concentration.Those results suggested that plasma Met concentration increased just at phase 2 when improved the level of methionine in diets.For further analyzed,the rations of SID-SAA/NE showed a gradual decrease in CON groups at phase 1-5,and the values is 2.71、2.22、1.92、1.66 和 1.41(g/MCal),respectively,and in methionine supplemental groups,while the SID SAA ratios in the methionine-supplemented diets were up to 3.39,2.78,2.40,2.07 and 1.76,respectively.As a result,compared with the previous control group,the least increase in the SID SAA ratio of the methionine-supplemented group occurred at phase 2,the ratio of which 2.78 is close to the ratio of the previous control group 2.71.In contrast,the methionine-supplemented groups at the rest phases had higher ratios than the previous control group.This results suggested that available energy intake showed significant effect on the plasma AA profile.3.Changes in meat quality and carcass characteristics:Longissimus muscle(LM)from pigs fed DLM and HMTBA treatments had both reduced(P<0.05)drip loss.Shear force of LM tended(P=0.06)to be decreased by increased consumption of TSAA.Interestingly,pH45min values was higher(P<0.05)in the HMTBA-fed gilts than in the DLM-and CON-fed gilts,while L*45min value was higher(P<0.05)in the HMTBA-fed barrows than in the DLM-and CON-fed barrows.4.Changes in biochemical indicators:Following increased consumption of methionine as either DLM or HMTBA,the content of muscle protein was decreased(P<0.05),meanwhile the content of crude protein in liver tended to decrease and total amino acids showed significant decrease(P<0.05).The glycolytic potential of LM was increased(P<0.05)by improving glucose and lactate concentration in DLM or HMTBA groups,respectively.Dietary HMTBA supplementation increased(P<0.05)short-chain fat acids concentrations and contributed to GLP-1 secretion(P<0.05).The HMTBA treatment showed lower(P<0.05)protein carbonyl content than the DL-Met treatment.5.Changes in the cross sectional area of myofibers and expression of genes in muscle:Decreased(P<0.05)CSA was observed in DL-Met and OH-Met treatments compared with the CON group.Compared with the CON treatment,the DL-Met and OH-Met treatment had decreased(P<0.05)mRNA abundance of MyHC ||x and IGF-1 while increased(P<0.05)mRNA abundance of FATP-1,GLUT-4 and AMPK2α,The GPR43 mRNA abundance was significantly higher(P<0.05)in the OH-Met treatment compared with the CON treatment.Base on the above results,it could be concluded that:(1)Increasing the level of SAA in dietsas either DLM or HMTBA had no effects on growth performance.Energy intake and the ratios of SID SAA to NE showed significant effect on the plasma AA profile,the ratio of SID SAA to NE is close to the previous control group may increase plasma Met concentration,low energy intake may promote conversion from Met to Tau.(2)The decreased shear force of LM was associated with the decrease in crude protein and increase in glycolytic potential.Changes in drip loss might be associated with the types of muscle fiber and the changes in protein oxidation in postmortem muscles.(3)Dietary HMTBA supplementation increased short-chain fat acids concentration in serum and promoted GLP-1 secretion,and thus contributed to lactate formation by improving the glucose oxidation and result in increasing muscle light.