Growth effects of lysine in compounded diets for American alligator, Alligator mississippiensis

Nutritional requirements of the American alligator, Alligator mississippiensis, are largely unknown despite the value of farm-raised alligator as an aquaculture product. We conducted a 10-month growth trial to determine effects of graded levels of dietary lysine on alligator growth as measured by increase in body length, body weight gain, and free lysine concentration in blood plasma. One-hundred-ninety-two hatchling alligators were fed 50% crude protein, pelletized diets, composed primarily of practical feed ingredients, with 1.5, 2.25, 3.0, or 3.75% dietary lysine. Diets were fed for 326 days under temperature-controlled, laboratory conditions. Body lengths and body weights were measured at 60-day intervals, and blood samples were taken at the final weighing. Increases in body length, body weight gain, and free lysine level in blood plasma indicated that a concentration of at least 2.25% dietary lysine (as fed)-about 4.5% of protein-was adequate for growth of alligator under the conditions of this study. Results suggest that the lysine requirement of American alligator is similar to requirements reported for other aquaculture species, including some fishes, crustaceans, and amphibians.