Effect Of Dietary Carbohydrate Level On Growth Performance And MRNA Expression Of Several Carbohydrate Metabolism Genes In Juvenile Darkbarbel Catfish, Pelteobagrus Vachelli

Carbohydrate is the cheapest feed nutrients, add the appropriate source of carbohydrate provides energy for the fish, which saves cost and reduces the consumed protein for energy sake in the feed. Although fish absorbs little carbohydrate, researches have shown that a certain addition of carbohydrate in the feed, promote the growth speed of fish and improve its body antioxident ability and immune function. Darkbarbel catfish, Pelteobagrus vachelli is China's special economic freshwater species, living in the bottom. As the breakthrough in artificial breeding in recent years, the scale and the breeding area of this fish have expanded. So far, however, the nutirtional requirements and feed development work are relatively weak, especially for carbohydrate nutritional requirementand the utilization rate is far more less.Combined with methods of the aquatic animal breeding science, the study of animal nutrition, biochemistry and molecular biology, and with the nutrients of carbohydrate as the starting point, this paper studies systematically the Darkbarbel Catfish, Pelteobagrus vachelli physiological difference, and carbohydrate's effect on its growth and survival rate. And it targetedly chooses the carbohydrate metabolism gene for its qualitaive and quantitative research, the result of this study provides a theoretical basis for further research of Darkbarbel Catfish,Pelteobagrus Vachelli of glucose metabolism,and reference for fully artificial feeding,which is of practical significance.It's divided into three parts:1. Study on the standard metabolism of the juvenile Darkbarbel catfish, Pelteobagrus vachelliThis study investigated the standard metabolism of the juvenile darkbarbel catfish, Pelteobagrus vachelli, in which the body weight were 6.23g,11.32g, and 21.21g respectively, the energy contribution of lipid protein and carbohydrate respective to the fish was also analysed. The respiratory rate, oxygen nitrogen ratio and specific energy consumption were obtained based on examing the oxygen consumption, carbon dioxide production rate and ammania-N excretion rate of the juvenile fish in fasting and resting state. The results showed that the oxygen consumption rate, ammania-N excretion rate and respiratory rate of the fish all decreased with the increase of the body weight(P<0.01),and oxygen consumption rate, ammania-N excretion rate and respiratory rate were correlated negatively with body weight, while the respiratory quotient was correlated positively with body weight. No significant correlation in carbon dioxide production rate and oxygen nitrogen ratio with body weight was found. Combined, all these findings indicate that juvenile darkbarbel catfish mainly utilize lipid and protein as energy sources, and with the growth of the fish, lipid could gradually become more important in energy provision. It was also found that the capacity of this species to utilize carbohydrate was limited, and it is necessary to condunct further study to understand its mechanism underlying.2. Effect of dietary carbohydrate level on growth performance in juvenile Darkbarbel catfish, Pelteobagrus vachelliA growth trial was conducted to evaluate the effects of dietary carbohydrate levels on growth performance, body composition and biochemical indices in serum of juvenile darkbarbel catfish, Pelteobagrus vachelli (average weight 1.0g±0.1g) for 70 days. Three isonitrogenous and isoenergetic experimental diets (40% crude protein and 17.6 kJ/g diet) using flour as the carbohydrate source, were formulated to contain three carbohydrate levels (7%,24% and 40% dry diet, respectively). The results showed that the 40% dietary carbohydrate level group got the highest weight gain, specific growth rate, protein efficiency ratio and the lowest feed conversion ratio, and there were no significant difference (P>0.05) between the 40%CHO and 24% CHO group. But the 7%CHO group showed the lowest weight gain, specific growth rate, protein efficiency ratio and the highest feed conversion ratio,and have significant difference (P<0.05) with other two groups. Analysed in biochemical indices in serum indicated that the blood glucose level rised with the increase of CHO,but there was no significant difference with all the group.The 40%CHO group blood glucose level was higer than the 24%CHO group slightly (P>0.05).The triglycerid levels and total cholesterol falled with the increase of CHO level. The 40%CHO group got the lowest level in triglycerid levels and total cholesterol, and has significant difference with the other two group(P<0.05). Based on this study, we considered the Pelteobagrus vachelli could adapt up to 40% dietary carbohydrate level, and the low carbohydrate level can made reduce of growth and feed efficiency.3. Effect of dietary carbohydrate level on mRNA expression of several carbohydrate metabolism genes in juvenile Darkbarbel catfish, Pelteobagrus vachelliGene clone technical was used for amplification of GK and PEPCK cDNA fragments of Darkbarbel catfish, Pelteobagrus vachelli, then used semi-quantitative real-time PCR to assay the expression of GK and PEPCK in liver under the different carbohydrate level as above. The results showed that, the level of carbohydrate in food can induce the expression of the two enzymes:the GK gene elevates along with the carbohydrate level advances, but PEPCK presents the tendency along with carbohydrate level advances. This result indicated that feed Darkbarbel catfish, Pelteobagrus vachelli with different level of carbohydrate for a long time can make a certain influence in metabolism, the high carbohydrate feed can promote the GK gene expression, will suppress the PEPCK gene the expression, the regulation seems to be similar to the mammals at least at the molecular level.