| High stocking density has been given a lot of attention,and much more researches were focused on the welfare problem.Methionine has been reported to promote growth and improve antioxidant capacity.This study determined the effect of supplemented methionine on relief negative influence and the demand for methionine under high stocking density,based on production performance,oxidative stress,the intestinal health indicators.The results are as follows:1.Effect of high stocking density on production performance and oxidative stress in broilersA total of 144 Arbor Acres broilers of 1 day old were selected,and were uniformly reared during 0-21 days old.At the end of 21 days of age,broilers were allotted to two different stocking densities with similar body weight.Stocking densities were set at 14 birds /m2(LSD)and 20 birds /m2(HSD).The results showed that: the ADFI,ADG and BW of the HSD broilers were significantly lower compared with the LSD(P<0.01).In HSD,the T-AOC was significantly declined(P<0.01),and the lysozyme was decreased(P<0.05);the CORT was increased(P<0.05),and the PCO,MDA,CK and ALT were increased significantly(P<0.01).The MDA in liver of HSD was increased(P<0.05),the HSP-70 gene expression was significantly higher(P<0.01),and the HMGCR gene expression was higher than LSD(P<0.05).Overall,the stocking density of 20 birds /m2 caused greater oxidative stress in caged broilers,weaken antioxidant capacity,and decreased production performance.2.Mitigation of oxidative stress in broilers by adding methionine in high stocking densityThe experiment was designed with 2×4 factors,576 one day old Arbor Acres broilers were selected,and uniformly reared during 0-21 days old.At the end of 21 days of age,they were divided into 8 groups with 6 repetitions separately.Stocking densities were set at 14 birds /m2(LSD)and 20 birds /m2(HSD),and methionine levels were set at 0.35%,0.4%,0.45% and 0.5%.The results showed that: 1)The mortality rate of broilers in HSD with 0.35% methionine level group was significantly higher than the other groups(P<0.01).2)The PCO in plasma of HSD was extremely significantly increased(P<0.01).The plasma of broilers in HSD with 0.45% methionine group,GPX was higher(P<0.01),and the CORT was significantlylower(P<0.01).Addition of methionine,the CK and LDH of broilers changed.The AST and ALT with the0.5% methionine group were higher(P<0.01).The ALT of HSD was significantly increased(P<0.01).3)Compared with the LSD,the spleen index,bursal index and lysozyme content of broilers in HSD were lower(P<0.05).The bursal index with the 0.45% methionine group were higher(P<0.05).4)The content of GPX and SOD in the liver of HSD with 0.45% methionine group was higher(P<0.01).The MDA in the jejunum with 0.35% methionine group was significantly higher than other groups(P<0.01).5)The liver expression of HSP-70 and HMGCR in LSD with 0.4% methionine group and the HSD with 0.45%methionine group was lower than other groups(P<0.05).The expression of Claudin-3 and Occludin in jejunum of broilers with 0.4% and 0.45% methionine groups was better.6)The broilers in LSD with 0.4%methionine group,have better jejunum height(P<0.01),lower the depth of crypt(P<0.01),the ratio of villus height to crypt depth was extremely higher than other groups(P<0.01),and the number of jejunal intraepithelial lymphocytes and goblet cells was significantly higher(P<0.01).In summary,HSD will cause oxidative stress in broilers,addition of methionine can reduce the mortality.When methionine level was0.45%,antioxidant performance and immune function was the best,liver metabolism and intestinal integrity were better.In conclusion,high stocking density of 20 birds /m2 can cause stress on broilers,affect the production and antioxidant performance of broilers.Addition of methionine can reduce the mortality.When methionine level was at 0.45%,antioxidant performance,immune function best,liver metabolism and intestinal integrity were much better. |
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