The effects of microencapsulated bovine insulin given to Litopenaeus vannamei juveniles as a feed additive on growth, metabolism, and digestive enzyme activities

Abstract

In recent years, insulin-like peptides have been identified, cloned, and their effects studied in several invertebrate species, such as fruit flies, bees, worms, and mollusks. Although insulin-like activities have been identified in lobster and crab species, there is little information about the roles of these peptides on other crustaceans. In this work, we examined the effects of microencapsulated bovine insulin used as a feed additive on several biochemical parameters of cultured Litopenaeus vannamei. We measured the variation in muscle and hepatopancreas glycogen, several hemolymph metabolites, and trypsin- and chymotrypsin-like activities in response to two doses of microencapsulated bovine insulin with respect to control individuals. We found that microencapsulated bovine insulin did not significantly stimulate weight gain in treated animals at the assayed doses. Insulin altered the use of hemolymph glucose, total proteins and hemocyanin during molt stages. Also, soluble digestive gland protein, trypsin-like activity, as well as hepatopancreatic and muscular glycogen were affected in relation to molt. Taken as a whole, our results suggest that at the assayed doses insulin administered to shrimp as a feed additive affects mainly the metabolism of carbohydrates and proteins, rather that acting as a growth hormone. In this sense, we provide evidence that a diet with 25 mg insulin per kg diet enhanced protein synthesis and hemocyanin improving possibly the shrimp immune condition.