| Methionine(Met)is the first limiting amino acid in maize soybean meal diets of poultry,a functional amino acid,which plays an important role in growth performance,intestinal development and health,antioxidant stress,and immunity.This study explored the changes in Met metabolic pathways and the effects on intestinal health supplemented with different sources and levels Met in the specific physiological state of heat stress.And it may provide a new way to improve the production efficiency of meat duck and to estimate the precise nutrition of Met on heat stress condition.A total of 720 four days old Peking ducks were randomly allotted to 6 dietary treatments.Each treatment consisted of 6 replicates with 20 ducks each.Ducks had free access to diet and water during the entire experiment.The feeding trial lasted 32 d and divided into a starter phase and grower phase.Starter diets were fed from d 4 to 16,while grower diets were fed from d 17 to 35.Graded levels(0.05,0.20 and 0.35%)of either DL-methionine(DLM,Adisseo SAS,Antony,France)or DL-2-hydroxy-4-methylthiobutyrate(HMTBA,Adisseo SAS,Antony,France)were supplemented to basal diet on equivalent basis,resulting in a total of 6 diets.The results are as follows:(1)In the starter period,body weight of per bird was striking increased(P<0.05)in the presence of HMTBA compared with supplementation of DLM.In accordance with body weight,there is a tendency(P<0.1)to improve ADG with the supplemental of HMTBA in the starter and whole period.Meanwhile a slightly increased(P<0.1)ADFI was also observed with the birds fed with HMTBA during the whole period.Regarding the levels of Met,there is a trend(P<0.1)to improve F/G with extra Met supplementation during the whole period.(2)In HMTBA supplemented groups,the p H value of ileum revealed an decrease compared with DLM supplemented groups on d 16(P<0.01).In gizzard,compared with the 0.05% Met supplementation,0.35% and 0.20% had a higher p H value on d 16(P<0.05).On d 35,the p H value of HMTBA supplemental groups was elevated compared to DLM supplemental groups in gizzard(P<0.05),and 0.35% Met supplementation compared with 0.05% had a significant addition(P<0.05).0.35% and 0.2% Met supplementation significantly reduced the expression of H~+-K~+-ATPase m RNA compared with 0.05% on day 16(P<0.01).Relative to 0.05% Met supplementation,the H~+-K~+-ATPase m RNA expression in proventriculus of 0.35% Met supplementation was lower on d 35(P<0.01).(3)The highest activities of AST,ALT and CK were determined in the plasma with 0.05% HMTBA-supplemented birds among all treatments(source × level interaction,P<0.05)on d 16.Supplemental HMTBA could decrease urea concentration on d 16(P<0.05).The level of supplemental Met had a significant effect on the concentration of urea and lower concentration was revealed in higher supplemental-Met level(P<0.05).Serum obtained from DLM treatments contained relatively higher(P<0.05)level of T4 compared with that from HMTBA-supplemented birds,regardless of the Met level in 35 d while HMTBA treatments increased the concentration of glucose,uric acid and urea(P<0.01;P<0.01;P<0.01)compared with DLM.The interaction between sources and levels of dietary Met significantly affect the concentration of HDL in serum on d 35(P<0.01),and 0.20% DLM supplemented birds significantly reduced the concentration of HDL compared with others.Compare to DLM,HMTBA supplemental birds significantly increased the concentration of TBA in serum on d 35.The level of supplemental Met significantly affect the concentration of TBA in serum on d 16(P<0.05),and 0.05% level treatment was the highest.(4)The interaction of Met resource and level significantly affected the concentration of MDA in serum on d 16 and 35(P<0.05;P<0.05),0.35% DLM contained the highest concentration of MDA.HMTBA supplemental birds significantly increased the concentration of T-GSH compared with DLM in serum on d 35(P<0.05).Also,the interaction of Met resource and level significantly affected the concentration of T-GSH on d 16(P<0.05),and the highest concentration was found in 0.05% HMTBA.Also,on d 35,0.35% DLM supplementation had the highest taurine concentration because of the interaction of Met resource and level(P<0.01).Also,0.20% HMTBA had the lowest Hcy concentration of serum on d 16(P<0.05).DLM supplementation significantly decreased the concentration of hepatic on d 16(P<0.01)and increased the concentration of hepatic T-GSH on d 35(P<0.05).Also,0.35% Met supplementation reduced protein carbonyl concentration compared with other two level treatment(P<0.05)on d 16,and 0.35% as well as 0.20% Met supplementation increased T-GSH concentration of liver on d 35(P<0.05).The interaction(resource × level)significantly affected hepatic taurine concentration as well as HSP70 m RNA expression on d 16 and 35(P<0.01;P<0.01;P<0.1;P<0.01),and 0.20% DLM supplementation contained the highest taurine,0.35% HMTBA supplementation significantly up-regulated the expression of HSP70 m RNA.(5)The addition of 0.35% level of Met could significantly increase the villus length(P<0.05)and its ratio to the crypt depth of the duodenum on d 16(P<0.05).The added Met source and level had a interactive effect on villus length and its ratio to the crypt depth of the duodenum on d 35(P<0.05;P<0.05),and the duodenum with 0.20% DLM group had the maximum length of villus length and its ratio to the crypt depth.Compared with the addition of HMTBA,the addition of DLM could significantly reduce the crypt depth of jejunum(P<0.01),and increase the length of villus(P<0.01)on d 35.The interactive effect of the addition of different Met source and level was found in villus length and its ratio to the crypt depth of ileum on d 16(P<0.05;P<0.05),and the addition of 0.05% of HMTBA showed the maximum length of the villus and the depth of the crypt.Compared with DLM supplementation,HMTBA supplemental birds significantly reduced the crypt depth(P<0.05)and increased the ratio of villus and crypt depth(P<0.05)of ileum on d 35.The concentration of MDA of ileum mucoso was significantly affected by the level of supplemental Met(P<0.05),and the MDA concentration of 0.20% supplementation was significantly increased compared with other two treatments.Also,the MDA concentration of jejunum mucoso was the highest in 0.35% supplementation compared with others(P<0.05).(6)The m RNA expression of IL-1?,GHR,HSP70,ZO-1 in duodenum were significantly affected by the addition of Met level(P<0.01;P<0.05;P<0.01;P<0.05),and increased Met supplementation could improve expression of these genes.The expression of IL-1?,HSP70 and ZO-1 m RNA in duodenum was significantly increased by supplemental DLM compared with HMTBA(P<0.01;P<0.05;P<0.05).The effect of supplemental DLM on the expression of GHR m RNA was significantly higher than that of HMTBA(P<0.01).The expression of GLP-2R m RNA in jejunum on d 16 was significantly increased by adding 0.35% Met compared with 0.05%(P<0.05).The expression of IL-1? and HSP70 m RNA in ileum on d 16 was significantly up-regulated by 0.35% level of Met compared with 0.05% and 0.20%(P<0.01;P<0.01).Compared with HMTBA supplementation,the expression of GHR,GLP-2R m RNA in duodenum on d 35 was up-regulated by the addition of DLM(P<0.01;P<0.05).The expression of IGF-1,GHR,ZO-1 and GLP-2R m RNA in jejunum on d 35 was significantly affected by the interaction of Met resource and level(P<0.01;P<0.01;P<0.01;P<0.01;P<0.01),and the expression levels of IGF-1,GHR,ZO-1 and GLP-2R m RNA were the highest at 0.35% Met supplementation.For the ileum on d 35,the addition of 0.35% Met in the group was significantly up-regulated the expression of ZO-1 m RNA compared with the other two groups(P<0.05).In summary,in the summer environment,the Peking duck feeding with HMTBA as a Met source helped to increase feed intake and body weight on d 16.0.35% Met supplementation up-regulated the expression of IGF-1,GHR,ZO-1,GLP-2R and HSP70 m RNA of small intestine and promoted the development of intestinal morphology in Peking duck on summer condition.Also,excessive Met may be associated with inhibition of gastric acid secretion. |
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