Research on the feed protein requirement of Cyprinus carpio haematopterus

Abstarct: The Yellow River carp (Cyprinus carpio haematopterus) is a unique and important freshwater economic fish that has naturally formed in the Yellow River Basin of China for a long time. Its demand for feed protein is lower than that of other carp. In order to explore the adaptation and utilization ability of Yellow River carp to different dietary protein contents in terms of growth traits, immunity and metabolism, yellow carp with initial body weight of (360.22±1.02) g were fed with test diets with protein contents of 22.63%, 25.32%, 28.15%, 31.43% and 34.18%. The results show that the weight gain rate, specific growth rate and protein efficiency in growth traits are highly significantly higher at 28.15% protein content than the other groups(P<0.01), and the feed coefficient is significantly lower at 28.15% than the other groups(P<0.05). Relative expression of growth genes GH, IGF-1 and protein synthesis genes TOR, 4EBP2 are significantly higher at 28.15% of protein content than 22.63%, 31.43% and 34.18% of test groups(P<0.05). Serum biochemistry levels of glutamic and glutamic aminotransferase are significantly lower in protein content 28.15% than in 22.63% and 34.18% test groups, but alkaline phosphatase levels are significantly higher in 22.63% and 34.18% test groups(P<0.05). The enzyme activities of α-Amylase, lipase, trypsin, superoxide dismutase, catalase, etc. And the content of reduced glutathione in the protein content 28.15% test group are significantly higher than those in the 22.63% and 34.18% protein content test groups(P<0.05), and malondialdehyde is highly significantly lower in 28.15% than in the other groups(P<0.01). The relative expression of Rhag, Rhbg and Rhcg1 among ammonia metabolism genes are significantly higher in 34.18% of protein content than other groups(P<0.05). The fit regression analysis show that the optimal dietary protein requirement of yellow river carp is about 28.57%~29.04%. This study helps to improve the feed protein utilization rate, reduce the feed cost, lay a theoretical foundation for the research and development of low nitrogen feed, and provide a theoretical basis for optimizing the nutritional ratio of carp formula feed.