| In present study, the effect of heat stress on the growth performance, welfare indicators, carcass traits, meat quality, intestinal mucosal morphology, HSP70mRNA expression of jejunal mueosa and serum antioxidant capacity for Cherry Valley Ducks were studied. Meanwhile, chromium picolinate was added to their diet in order to alleviate effect on heat stressed ducks. It aimed to provide scientific basis for further study on the mechanism of duck heat stress and theoretical guidance to alleviate heat stress for nutritional regulation.The experiment selected one day-old, healthy,180birds, whose initial average body weight was60±5g. Ducks were randomly allocated into three groups, each group of five replicates and each repeated12birds. Control group, at ambient temperature of21-25℃by air-conditioning; heat stress group, in Wuhan, Hubei Province in August under natural conditions, at ambient temperature of28-35℃; organic chromium group, under the heat stress condition, at ambient temperature of28-35℃, add0.2mg/kg chromium picolinate (with chromium) to the normal diet.then a35-day feeding trial begun. Ducks were slaughtered on the day of14,21,35.The results were as follows:(1) Heat stress and organic chromium had no significant effect on growth performance for ducks on1-21day and22-35day (P>0.05). At day21, heat stress significantly increased ducks’FA for leg length (P<0.05). At day35, heat stress can significantly increase proportion of which gait score was1(P<0.05); organic chromium significantly increased heat stressed ducks’quality of feathers (P<0.05); organic chromium significantly decreased proportion of which gait score was1for heat stressed ducks (P<0.05).(2) At day35, heat stress can significantly reduce the live weight, carcass weight, semi-eviscerated weight, eviscerated weight, heart weight, spleen weight (P<0.05). Heat stress can significantly reduce esophagus weight and jejunum length (P<0.05). Organic chromium can significantly increase final pH for heat stressed duck (P<0.05).(3) At day14, heat stress significantly increased jejunal crypt depth (P<0.05), organic chromium significantly increased jejunal villus height/crypt depth ratio of heat stressed group (P<0.05); jejunal mueosa HSP70mRNA expression for heated stress group was significantly higher than that of the control group (P<0.05), organic chromium can significantly reduce the expression of jejunal mucosa HSP70mRNA of heated stress duck (P<0.05). At day21, ileal villi height in heat stressed ducks was significantly lower than that of control group (P<0.05). organic chromium can significantly increase heat stressed ducks villi height:crypt depth ratio (P<0.05). At day35. heat stress can significantly reduce jejunum villus height/crypt depth ratio (P<0.05); jejunal mucosa HSP70mRNA expression of heat stress group was significantly higher than that of the control group (P<0.05), organic chromium had no significant difference for heat stressed ducks on intestinal mucosal morphology and jejunum mucous HSP70mRNA.(4) At day14, heat stress significantly increased the content of malondialdehyde (MDA) in serum (P<0.05), organic chromium can significantly reduce the content of MDA for heat stressed ducks (P<0.05). At day21, heat stress can significantly reduce the T-SOD activity (P<0.05), while T-SOD activity in organic chromium group, was significantly higher than heat stress group (P<0.05). At day35, T-AOC activity in heat stress group was significantly lower than the control group (P<0.05), and organic chromium can significantly increase heat stressed ducks’T-AOC activity in serum (P<0.05).Above of all. the conclusions were:Heat stress reduced feed intake, welfare indicators, carcass traits, meat quality. increased crypt depth, decreased villus height/crypt depth ratio. Also, expression of the jejunum mucous HSP70mRNA was higher, serum antioxidant capacity was reduced. Adding organic chromium to the diet of heat stressed duck, to some extent, can improve intestinal morphology and antioxidant capacity for heat stressed ducks. |
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