Effect of Different Carbohydrate Sources on Daily Weight Growth, Feed Utilization and Digestive Enzyme Activities of Trachinotus ovatus

Abstract:

A cost-efficient formula of feed in fish farming usually contains a large amount of low-cost energy sources supplemented with sufficient level of high-cost essential nutrients such as protein. Carbohydrate is the least costly dietary energy for animals. However, the utilization of carbohydrate varies a lot between different fish species, and the mechanisms underlying distinctive carbohydrate-consuming abilities have been obscure. In this study we aimed to explore the effects of different carbohydrate sources on daily weight growth (DWG), feed utilization and digestive enzyme activities of Trachinotus ovatus. Fish (initial weight 31.24±0.58 g) were fed with 5 groups of isonitrogenous and isolipidic diets each of which contained 1 type of carbohydrate at 20% including glucose, sucrose, dextrin, corn starch or gelatinized corn starch. Each group was fed for 8 weeks. The results showed that different carbohydrate sources significantly affected the DWG, feed efficiency (FE) and the protein efficiency ratio (PER) (P<0.05). The gelatinized corn starch group had significantly higher DWG (2.19 g/d), FE (0.82%) and PER (1.88) than other groups (P<0.05), and there was no significant difference between the two starch groups (P>0.05). The glucose group had the lowest DWG, FE and PER (P<0.05). Dietary carbohydrate sources also had great effects on activities of digestive enzymes (P<0.05). The protease activity of the two starch groups was significantly lower than that of the other three groups (P<0.05). The sucrose group displayed the highest amylase activity (P<0.05). The lipase activity was boosted along with the increase in the molecular weight of the dietary carbohydrate, and was the highest in the gelatinized corn starch group. In conclusion, large-molecule carbohydrates may have better effects on the growth of T. ovatus than glucose, sucrose and dextrin. Gelatinized corn starch was the optimal carbohydrate source in this study.