A comparison of two sources of methionine supplemented at different levels on heat shock protein 70 expression and oxidative stress product of Peking ducks subjected to heat stress.

The aim of this study was to examine the effects of different sources and levels of methionine (Met) on Heat shock proteins HSP70 expression and protein carbonylation in liver, HSP70 expression and malondialdehyde (MDA) concentration in intestine under heat stress conditions during summer. A total of 720 (4 days old) Peking ducks were placed 20 per pen into six replicates for each of the six treatments with a 2 × 3 factorial arrangement, such that two sources of Met (DL-methionine [DLM] and DL-2-hydroxy-4-methylthiobutyrate [HMTBA] were supplemented at three different levels (0.05%, 0.20%, or 0.35% on as-fed basis respectively). The experiment was divided into a starter (day 4-16) and a grower (day 17-35) period. Diet supplemented with 0.35% Met significantly up-regulated the HSP70 mRNA expression in duodenum, jejunum and ileum on day 16 and 35 as well as in liver on day 35 (p < .05) of ducks. HMTBA-supplemented diets increased the HSP70 mRNA expression in duodenum, jejunum, ileum and liver on day 35 (p < .01). An increased MDA concentration was detected in jejunum of birds in 0.35% DLM-supplemented treatment on day 16 (p < .05). And decreased protein carbonylation concentration was found in DLM-supplemented treatment on day 16 (p < .01). The birds fed with 0.35% Met supplemental diet displayed lower hepatic protein carbonylation on day 16 (p < .05). In conclusion, supplementation of 0.35% Met in the duck diet showed up-regulated HSP70 expression in small intestine and liver, which may provide new perspective to the mechanism of Met function. At the same time, DLM supplemented in diet may ameliorate oxidative status of liver, while HMTBA supplementation may partially improve the intestinal oxidative status of Peking ducks.