Dietary energy sources for the American alligator, Alligator mississippiensis (Daudin)

Abstract

Three experiments were conducted to evaluate responses of alligators to dietary inclusion of fat, carbohydrate or vegetable protein. Dilution of a high-protein, low-fat, carbohydrate-free diet with graded levels of fat (3.6–16.6% dietary dry matter) resulted in significantly greater body weight gains and improved feed conversion. Percent carcass fat was greater with increased dietary fat. Digestibility of protein (87.3–89.2%) and energy (84.6–86.8%) decreased slightly with increases in caloric density of the diet. Digestible energy (DE) and a nitrogen-corrected digestible energy (DE n) increased with dietary gross energy. A second experiment compared two high-protein diets (meat and a purified diet) and the effects of supplementing these diets with glucose or extruded corn as 20% of dietary dry matter. The purified diet led to greater gains in body weight than the meat diet. Supplementation with corn did not significantly influence performance. Glucose supplementation of meat significantly improved body weight gains, but similar supplementation of the purified diet decreased performance. In a third experiment, alligators fed a carbohydrate-containing diet consumed significantly more feed and gained significantly more weight than those fed diets with protein as the corresponding energy source. Digestibility of protein, approximately 40% of which was isolated soybean protein, was very high (96.0–97.1%). Variation in energy digestibility (78.5–91.3%) was related to dietary fiber content. Liver lipogenesis from acetate was generally greater than from leucine and glucose. However, for alligators fed the carbohydrate-containing diet, liver lipogenesis from glucose and acetate was not significantly different. In several experiments, carcass and adipose tissue fatty acids were generally reflective of dietary treatment. However, stearic acid levels were low and unaffected by diet.