The Effect Of Metallothionein Induced By Zinc&Copper On Ascites Syndrome In Broilers

Ascites syndrome (AS) in broiler chicken is a kind of nutritional and metabolic disease mainly characterized by the symptoms bellow:right ventricular hypertrophy, heart failure, ascites and so on. It was fisrt seen in the plateau region, but in recent years, it happened more and more in common place. In the world scale, the disease caused one billion dollars economic losses in poultry industry every year and gained high attentions of domestic and foreign scholars. Some scholars think that the pursuit of high growth rate in genetics and breeding is a main cause, which resulting in enhanced metabolism and increased need for oxygen requirements and produced more electron leakage during the oxidative metabolic course. Thus caused the heart, liver, lung, kidney and other organs damagement and finally turned out to be AS. Metallothionein (MT) is a kind of protein with a strong antioxidant capacity, which may help the body to defence the oxidant damage. The research is based on the radical damage theory of AS in broiler chicken, and different dosage of zinc and copper was added to food to induce metallothionein expression and observe the effect of MT to AS, so as to provide a new way of prevention and treatment of the disease.Part I The effect of MT induced by zinc on ascites syndrome in broilers.30015-day-old AA+commercial broilers were randomly divided into five groups (based on the basal dietary content, they were natural temperature group (NT group), low temperature+T3group (LT+T3group), low temperature+T3+Zn100mg/kg (Znl) group, low temperature+T3+Zn150mg/kg (Zn2) group, low temperature+T3+Zn200mg/kg diet (Zn3) group). From15d on, the room temperature (except the natural temperature group) was slowly decreased1℃-2％a day till it came to12℃-14℃by21d. Except for the natural temprature group, the4other groups add3-triiodothyronine (T3) to induce ascites syndrome in broilers. From22d on, we weight the chicken by fasted one night and get the samples every week. We statisticed the incidence of AS and detected the value of RV/TV, PCV, Hb content, examined the serum AST, AKP, UA, LDH value, mesured MT expression in liver and kidney by immunohistochemisty and checked the items associated with antioxident ability such as T-AOC, T-SOD, GSH-Px and MDA. Calculated the growth performance, feed conversion rate and accounted the immune organ index. Compared to the NT group, the results showed that the incidence of AS in LT+T3group significantly increased (P<0.01), while the other three groups were extremely decreased; the value of RV/TV, PCV, Hb value of the LT+T3was significantly different (P<0.05) to the other groups in the latter weeks, the serum biochemical enzame such as the AST value changed dramatically (P<0.05). MT expression in liver and kidney in the groups added zinc significantly increased (P<0.05) and the whole antioxident ability increased, at the same time the MDA value decreased. Chicken in the groups added Zn grow more quickly and the food conversion rate was lower than the other ones, and there were nearly no bad effect to the immune organ index. Conclusion:Added Zn to the dietary can decrease the statistical incidence of AS to a certain extent. Zn also increased the MT expression and enhanced the body’s antioxidant ability, promote the growth of the body, and the dosage is effective and safe. The dose of zinc about100mg/kg and150mg/kg is much better in preventing AS in broilers.Part Ⅱ The effect of MT induced by copper on ascites syndrome in broilers.30015-day-old AA+broilers were randomly divided into five groups (NT group, LT+T3group, LT+T3+Cu150mg/kg group, LT+T3+Cu200mg/kg group, LT+T3+Cu250mg/kg group). From22d on, we take the samples every week just like described in the part Ⅰ and statistic those values. We also calculated the incidence of AS and RV/TV, PCV, Hb value and examined AST, AKP, UA, LDH value in serum, mesured MT in liver and kidney by immunohistochemical technology, examined three antioxident ability associated items and the MDA value, and statisticed the growth performance, feed conversion rate and the immune organ index. The results showed that the incidense of the LT+T3group was significantly increased (P<0.01), and the incidence of AS in the groups added copper were decreased. The RV/TV, PCV, Hb value and serum biochemical enzame of the LT+T3is significantly difference (P<0.05) from the other groups in the latter weeks. MT expression in liver and kidney in groups added copper was significantly increased (P<0.05) and the serum antioxident ability was enhanced during the trial. Conclusion:Added copper to the dietary can reduce the incidence of AS by a certain extent, and MT was much more induced by Cu and the serum antioxident ability was incresed. Cu helped the broilers grow quickly and got better food conversation raito, there were nearly no bad effect to the immune organ index. The copper dosage near150mg/kg was better for proventing AS in broilers.