Insulin Response of Largemouth Bass to Glucose, Amino Acid, and Diet Stimulation

Abstract

AbstractInvestigation of the dietary requirements of largemouth bass Micropterus salmoides has intensified because of the popularity of this species. To determine commercial diets containing carbohydrate concentrations that are not detrimental to the health and survival of largemouth bass, we examined the effects of carbohydrate loads on insulin response. This study was intended to characterize the insulin response of largemouth bass to diet, glucose, and amino acids. Pellet‐trained largemouth bass were either orally stimulated with glucose, lysine, arginine, or methionine or fed a commercial pelleted diet or a “natural” diet of golden shiners Notemigonus crysoleucas, then bled over time to ascertain their insulin response. Insulin response was correlated with glucose response, the insulin responses lagging slightly behind increases in blood glucose concentration. Greater increases in blood glucose were accompanied by sharper, quicker insulin responses. Glucose (4.8 ± 0.3 ng insulin/mL) and arginine (5.4 ± 0.4 ng/mL) stimulation evoked the greatest mean insulin responses at 60 min postadministration; lysine (2.1 ± 0.3 ng/mL) also produced elevated insulin responses. The pelleted diet stimulated an intermediate response, whereas the diet of golden shiners produced the lowest insulin response. This study was intended to determine how the carbohydrate content of diets and subsequent influences on insulin response affect the health of largemouth bass. Because of confounding effects and interference from arginine and lysine in the diet, insulin response is not suitable for determining appropriate carbohydrate loads in largemouth bass diets. At this time, histological data and liver glycogen concentration should be used to determine appropriate carbohydrate loads in commercial diets.