Influences Of Manganese On Production Performance, Biochemical Parameters And Gene Expression Of Mn-SOD In Growing Rex Rabbits

Rex rabbits are extensively consented and accepted by consumers more and more. Because of providing nutritional meat and high-quality fur, rex rabbits are regarded as a good species for breeding.The nutrition research of rex rabbits fairly fall behind other animals.There is not a unified breed standard at present. For satisfying the need of market and acquiring economic value, researchers must make efforts on nutritional requirements of the rex rabbit and set a unified standard eventually. Based on practical diet, we investigated the effects of different manganese concentrations in diet on production performances and biochemical parameters, and explored the relationship between phenotypic character and manganese concentrations from molecular level. We hope this research could provide the scientific evidence of nutrition standard of the rex rabbit under productive conditions. 72 rex rabbits of 50 days were randomly divided into 6 groups. On the bases of corn-bean diet, manganese of 0,5,15,25,35,45mg/kg were added to the dietary respectively. We continuously observed and gained production performances and biochemical parameters for two months. Moreover, we applied RT-PCR to detect the expressing levels of manganese hemocuprein(Mn-SOD) in hearts of experimental rex rabbits.The results as follows: Daily gain and feed:gain were affected significantly by manganese concentration in diet(P<0.05), on the contrary of area of hide(P>0.05). Increasing manganese concentration in diet promoted the growth of rex rabbits. One of important reasons was that increasing manganese synthesis of DNA and proteins. In addition, improving clearance of superoxide radical anion and protecting cells by the enhancement of Mn-SOD with increasing manganese concentration. The sediment yields of manganese in bone and fur were significantly affected by manganese concentration in dietary(P<0.01), and there was a direct ratio between them. In liver and kidney, there was a increasing tendency of the sediment yields with manganese concentration(P>0.05). When manganese concentration reached to 35mg/kg in diet, the manganese content in bone and fur obviously rose. Accordingly, the amplification decreased with manganese concentration raising to 45mg/kg. It illustrated that there was an inflection point in 35mg/kg addition of manganese in diet. From the manganese content in tissues, 35mg/kg manganese in diet could satisfy the requirement of rex rabbit. Through analyzing dependability between manganese concentration in dietary and sediment yield in tissues, we discovered the highest coefficient correlation was in fur ,then in bone and liver. Therefore, manganese concentration in bone and fur might be a sensitive index, that evaluated availability of manganese in diet. Significant effects of manganese concentration in diet on alkaline phosphatase glutamic, oxalacetic transaminase,glutamate-pyruvate trans aminase in serum were not apparent.Firstly,as many literature recorded the high content calcium and phosphours in dietary could depress the manganese availability. Secondly,calcium,manganese,magnesium,barium and cobalt all were the reactivators of alkaline phosphatase glutamic,but calcium was the best.At present, it was thought that the mechanism of effecton manganese availability was "Ca-P-Mn"compounds theory,that was lots of calcium and phosphatase compound absorbing manganese and affecting manganese availability under alkaline circumstance in duodenum. As for oxalacetic transaminase and glutamate-pyruvate transaminase, their activity were repressed with increasing manganese concentration in diet, but the mechanism was not clear. Manganese concentration in diet significantly affected MnSOD activity in cardiac muscle,both of them increased at the same time, but it is not as obviously as in serum.Because manganese in diet was quickly absorbed by organism and distributed to all over the body, there was not an obvious influence of manganese on MnSOD activity in serum. Meanwhile, as a prothetic group of MnSOD, manganese concentration in diet could cause the variation of MnSOD activity in cardiac muscle, but there must be a more complicated mechanism.Borrello(1992)reported that Mn-SOD activity decreased in the mice of manganese deficiency, and thought the mechanism could be transcription blockage. With increasing manganese concentration in dietary, mRNA level of MnSOD rose in cardiac muscle. It illustrated that manganese improved the transcription of Mn-SOD, and promoted Mn-SOD activity simultaneously. So we could thought there was a dependability between manganese concentration and Mn-SOD in cardiac muscle. According to many references, the transcription of Mn-SOD gene might be controlled by a promotor, and there were many sensitive regulatory elements in gene order. The effects of manganese on Mn-SOD were possibly implemented by promotor and regulatory elements. In the future, the specific molecular mechanism will be still researched and comprehended.