| Methionine(Met)is an essential amino acid of livestock and its additive products have been widely used in feed industry.There are many commercial methionine products which are possessed of different biological values.However,the biological values of some products(DL-Met and MHA-Ca)in pigs were not clear,and it will impact the using effects in practical production.Therefore,it is necessary to study the biological value and underlying mechanisms of the different methionine product on nitrogen deposition of piglets.This study was conducted to investigate the biological values of DL-Met and MHA-Ca compared to L-Met,futhermore,to expore the possible differences of three kinds of methionines on metabolism and antioxidation in piglets.This study consisted of three experiments.The first one and the second one were conducted to investigate the biological values of DL-Met and MHA-Ca compared to L-Met;the third one was on the data basis of the first and second experiment to estimate the effects of the three methionines on the growth performance,intestinal morphology,antioxidant capacity and methionine metabolism-enzyme genes expression in piglets.Experiment one Biological value of DL-Met in pigletsA total of 42 healthy DLY(Duroc × Landrace × Yorkshire)piglets with an initial average body weight of 14.75 ± 0.10 kg were randomly allotted to 7 treatments.Each treatment has 6 replicates,each replicates has 1 pig.Pigs were fed by basal diet(no addition of methionine)and basal diet supplemented with 0.025%,0.050%and 0.075%L-Met or DL-Met for 12 days.During days 8-12,all pigs were controlled by metabolism experiment and were obtained samples of feces and urine.Each pig was weighed after 12 h fasting in the morning of day 1,day 8 and day 13.The results were shown as follows:(1)Compared to basal diet,dietary supplementation with L-Met or DL-Met increased the ADG and FCR of piglets at dose-dependent.(2)Compared to basal diet,dietary supplementation with 0.075%L-Met or DL-Met significantly increased the FCR of piglets in the whole feeding period(P<0.05),and the 0.050%DL-Met diet also had the same effect(P<0.05).(3)According to the relationship between the amount of nitrogen retention and the supplement of L-Met or DL-Met in piglets,the fitted equations were y=32.310x1+11.902(x1 was the supplemented dose of L-Met,R2= 0.939,P<0.05)and y=31.971x2+11.848(x2 was the supplemented dose of DL-Met,R2= 0.945,P<0.05),respectively.Therefore,the biological value of DL-Met compared to L-Met was equal to 98.95%.Experiment two Biological value of MHA-Ca in pigletsA total of fourty two healthy DLY piglets with an initial average body weight of 12.13± 0.08 kg were randomly allotted to 7 treatments.Each treatment has 6 replicates,each replicates has 1 pig.Pigs were fed by basal diet(no addition of methionine)and basal diet supplemented with 0.025%,0.050%and 0.075%L-Met or basal diet supplemented with 0.030%,0.060%and 0.089%MHA-Ca(contained 0.025%,0.050%and 0.075%MHA,respectively.)for 12 days.During days 8-12,all pigs were controlled by metabolism experiment and were obtained samples of feces and urine.Each pig was weighed after 12 h fasting in the morning of day 1,day 8 and day 13.The results were shown as follows:(1)Compared to basal diet,dietary supplementation with L-Met or MHA-Ca increased ADG and FCR of piglets at dose-dependent.(2)Compar,ed to basal diet,in 1-7 days,dietary supplementation with 0.050%L-Met significantly increased ADG of piglets(P<0.05),and 0.075%L-Met diet also significantly increased ADG and FCR of piglets(P<0.05).In the whole feeding period,dietary supplementation with 0.050%and 0.075%L-Met or 0.089%MHA-Ca increased ADG and FCR of piglets(P<0.05).(3)According to the relationship between the amount of nitrogen retention and the supplement of L-Met or MHA-Ca in piglets,the fitted equations were y=26.074x1+8.677(x1 was the supplemented dose of L-Met,P<0.05)and y=17.040x2+8.841(x2 was the supplemented dose of MHA-Ca,P<0.05),respectively.Therefore,the biological value of MHA Cacompared to L-Met was equal to 65.35%.Experiment three Effects of different methionine on its metabolism and antioxidantion in pigletsA total of ninety six healthy DLY piglets with an initial average body weight of 13.24± 0.05 kg were randomly allotted to 4 treatments.Each treatment has 6 replicates,each replicates has 4 pig.Treatment pigs were fed by basal diet(no additionalmethionine,lack of Met and Cys);basal diet + 0.138%L-Met(dietary SID Met content was 0.360%,biological value of L-Met was 100%);basal diet + 0.139%DL-Met(dietary SID Met content was 0.360%,biological value of DL-Met was 98.95%);basal diet + 0.211%MHA-Ca(dietary SID Met content was 0.360%,biological value of MHA-Ca was 65.35%)for 28 days.One piglet with a close average BW per replicate was chosen for bleeding via the jugular veins in the morning of 29 day.After blood sampling,these pigs were slaughtered to obtain tissuesto be measured.The results were as follows:(1)Compared to basal diet,dietary supplementation with the same effective contents of L-Met,DL-Met or MHA-Ca significantly increased FCR of piglets(P<0.05),but there were no differences among these three Met treatment diets.(2)Dietary supplementation with different Met or without Met had no significant effect on stomach,jejunum,ileum and cecum digesta pH values of piglets.(3)Compared to basal diet,dietary supplementation with same effective contents of L-Met,DL-Met or MHA-Ca tended to increase the villous height of duodenum in piglets(P = 0.09),and MHA-Ca diet also tended to increase the ratio of villous height/crypt depth of duodenum in piglets(P = 0.10).However,these three Met treatment diets had no effect on the intestinal morphology of piglets.(4)Compared to basal diet,dietary supplementation with same effective contents of L-Met or DL-Met increased the plasma level of GSH of piglets(P<0.05),however,there was a little effect of MHA-Ca on the plasma level of GSH of piglets.(5)When compared with basal diet,dietary supplementation with same effective contents of L-Met,DL-Met or MHA-Ca significantly increased the level of GSH and the ratio of GSH/GSSG in the liver(P<0.05),had no effect on the levels of MDA,PCO,H2O2,GSSG and activities of CAT and T-AOC in the liver.Dietary supplementation with L-Met,DL-Met or MHA-Ca increased the level of GSH in jejunum mucosa of piglets(P<0.05),but there were no differences among these three Met treatment diets.Supplementation with DL-Met or MHA-Ca significantly increased T-AOC in jejunum mucosa(P<0.05),however,DL-Met diet reduced the activity of CAT in jejunum mucosa(P<0.05).When compared with L-Met diet,the MHA-Ca diet increased the activity of CAT in jejunum mucosa(P<0.05).(6)When compared with basal diet and L-Met diet,the DL-Met diet increased DAAO mRNA relative expression in the liver(P<0.05).When compared with L-Met diet,the MHA-Ca diet increased HADH mRNA relative expression in liver(P<0.05).L-Met diet reduced MAT1? gene relative expression in liver and ileum(P<0.05)compared to the basal diet.When compared with basal diet,L-Met and MHA-Ca diet,the DL-Met diet increased the C?S2 mRNA relative expression in the jejunum(P<0.05).In addition,dietary supplementation with different Met or without Met had no significant effect on the HAO1,MAT2?,MAT2? mRNA expressions in the liver,DAAO,HADH,MAT1?,MAT2?,MAT2?,C?S2,CTH mRNA expressions in the jejunum and DAAO,HADH,MAT2?,MAT2?,C?S2,CTH mRNA expressions in the ileum.In conclusions,our results demonstrated that:(1)According to the slope ratio method of nitrogen deposition data,the biological values of DL-Met and MHA-Ca compared to L-Met were 98.95%and 65.35%,respectively.(2)Dietary supplementation with different methionines improved the growth performance and antioxidant capacity of piglets.Supplementation with DL-Met or MHA-Ca had no difference in efficacy with L-Met.(3)Expression of the genes which DL-Met and MHA-Ca transformed to L-Met(DAAO for D-Met,HAO1 and HADH for MHA-Ca)and L-Met metabolism-related enzymes(MAT1?,MAT2?,MAT2?,C?S2 and CTH)were measured in the liver and jejunum.Dietary supplementation with different methionine sources up-regulated the specific L-Met transformation enzymes in the liver.However,these three methionine sources did not impact the expression of mRNA of L-Met metabolic enzymes in liver or jejunum. |
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