Sixty-six captive-reared, juvenile alligators maintained in environmentally controlled chambers were randomly assigned to four treatments consisting of stocking densities of 0.35, 0.18, 0.12, and 0.09 m'/alligator. Alligators were maintained at these densities for 3.5 months. At approximately 4 week intervals the alligators were weighed, measured, and bled via cardiac puncture. Duplicate aliquots of plasma were assayed for corticosterone. All of the alligators continued to grow during the experiment, but alligators maintained a t the lowest stocking density were significantly heavier and grew significantly faster (P < 0.01) and had significantly lower plasma corticosterone (P < 0.01) than alligators maintained a t the highest stocking density. These results indicate that crowding (i.e., high-density rearing) of juvenile alligators inhibits maximum growth and that the subsequent stress associated with this crowding results in chronically elevated plasma corticosterone. Plasma corticosterone showed a strong negative correlation with change in body weight; the faster the rate of growth, the lower the hormone levels. These results also show that a single blood sample taken at monthly intervals is sufficient to monitor chronically elevated plasma corticosterone in this species.
First-year alligators (Alligator mississippiensis) averaging 377-857 g body weight were fed diets containing various levels of protein, fat and carbohydrate. In experiment 1, nine diets arranged in a centrally rotatable composite design contained 0-36% extruded corn and 4-20% total fat. Response surface analysis predicted maximum responses in performance criteria at 6.3-18.8% corn and 15.8-27.4% fat. Corn inclusion at up to 27-36% of diet resulted in equal or improved performance compared to carbohydrate-free diets of equal fat content. Energy digestibility averaged 84.3%. Protein digestibility averaged 86.7%. Maximum responses in performance criteria were predicted at 42.5-48.7% digestible protein and 4367-4421 kcal/kg digestible energy. In two additional experiments, alligators were either fasted or fed for various numbers of days/week. Carbohydrate-supplementation of high protein diets led to equal or significantly improved performances. Performance was maximized by feeding the alligators 5-6 d/w. Regression of body weight changes against energy and protein intake yielded estimates of daily maintenance requirements of 5.7-8.4 kcal and 0.49-0.89 g protein/kg live body weight. Dietary fat and carbohydrate in the forms and amounts fed to young alligators were well-utilized. Optimal digestible energy:crude protein ratios (8.2-10.9:1 kcal/g protein) were similar to those of other aquatic ectotherms of equal size.
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