Effects of different levels of dietary folic acid on the growth performance, muscle composition, immune response and antioxidant capacity of freshwater prawn, Macrobrachium rosenbergii

Abstract

A 12-week feeding trial was conducted to determine the effects of dietary supplementation with folic acid on growth performance, digestive enzyme activity, muscle composition, immune response, antioxidant ability and enzyme activity of freshwater prawn Macrobrachium rosenbergii. The experimental basal diets were supplemented with folic acid at the rates of 0 (control), 0.5, 1.0, 2.0, 4.0, 8.0mg/kg dry feed weight. The as-supplemented folic acid was fed in M. rosenbergii for a period of 90days. The experimental study demonstrated that final body weight, weight gain, specific growth rate and feed conversion ratio significantly (P<0.05) increased with an increasing dietary folic acid level of up to 0.5–2.0mg/kg. However, the prawns fed with above 4.0–8.0mg/kg showed poor performance. Addition, prawns fed with 0.5–2.0mg/kg of folic acid supplemented diets achieved significant (P<0.05) improvement in growth performance, digestive enzyme activities, and muscle biochemical compositions, while, the prawns fed with 2.0mg/kg of folic acid showed enhanced performance respectively. Prawn fed on diet supplemented with 2.0mg/kg of folic acid showed significantly (P<0.05) higher total protein level. The antioxidants enzymatic activity (SOD, CAT) metabolic enzymes status in muscle showed no significant (P>0.05) alterations in prawns fed with 0.5–2.0mg/kg of folic acid supplemented diets. Therefore, the present study proposed that 2.0mg/kg of folic acid could be supplemented for flexible enhanced survival; growth, antioxidant defense system and production of M. rosenbergii. Statement of relevanceVitamins are considered as low molecular weight organic compounds that are required in small amounts for the maintenance of metabolism, normal growth and health of fish. Folic acid is a form of water-soluble vitamin B9, which is important in amino acid and nucleotide metabolism, growth and health of most aquatic animals. The crustacean, giant freshwater prawn, Macrobrachium rosenbergii is a major species by yielding high fecundity, rapid growth, wide range of salinity and possessing unique characters such as temperature tolerance, disease resistance as well as its superior taste and high commercial value etc. The global production of M. rosenbergii has increased from 130,689tons in 2000 to 203,211tons in 2011. There is also representing good nutritional source of proteins, essential amino acids, poly-unsaturated fatty acids and low in fat. Therefore, it can be used as a delicious healthy choice of food for human consumptions. There are many researches about its nutritional requirements, but limited information was published concerning the vitamin requirement and nutritional function. Furthermore, there is no information about antioxidant effect and serum biochemistry parameters of folic acid on M. rosenbergii, which are important factors affecting prawn's health. In view of this knowledge, in the current study was hypothesized that the efficiency of dietary folic acid supplemented and its effect were further assessed on survival, growth, activities of digestive enzymes, muscle biochemical compositions, carcass mineral contents, activities of antioxidant and activities of metabolic enzymes of freshwater prawn M. rosenbergii.