64 MARCH 2016 • WORLD AQUACULTURE • WWW.WAS.ORG to all alligators during the first 14 weeks followed by a 50-percent protein diet during the final 10 weeks. Regardless of the diet fed, one group (12 randomly selected tanks) received a single daily feeding at 0800 h of a weight of diet equal to approximately five percent of the total weight of alligators in each tank. The second group (12 tanks) received two feedings per day, at 0800 and 1400 h, of a weight of the same diet equivalent to five percent and 2.5 percent, respectively, of the total weight of alligators in each tank. The percentages were chosen, based on experience in earlier feeding trials, to ensure that the diet was provided in excess at each feeding so the animals could feed to satiation. Alligator lengths and weights were measured monthly to track growth and adjust feed allotments. Between monthly measurements, diet allotments were increased as necessary in individual tanks to ensure that there was always feed remaining in every tank when the animals had finished eating (45-60 min). Twice per week, uneaten diet was collected from each tank with a net, air-dried overnight under an electric fan to approximately 10 percent moisture and weighed to determine feed consumption of alligators in each tank. commercial alligator growout and within the preferred temperature range of American alligator (Johnson et al. 1978, Asa et al. 1998). Tanks were operated as individual units with separate inflow and outflow pipes. Each tank received a continuous flow (0.38 L/min) of geothermally heated water (31 C from a 762m deep well). Desired water temperature was maintained by holding room air temperature at 32 C with a 73,268 J/s (250,000 BTUH) natural gas, forced-air heater and by the presence in each tank of a 1-kW, computercontrolled, immersion water heater. Every 24-72 h, tanks were completely drained, rinsed with warm water, and refilled with clean, 31 C water to a depth of 30 cm. Alligators with an average initial length of 49 cm and weight of 329 g were stocked at eight animals per tank and subjected to one of two feeding regimens for 169 days. Alligators were marked with metal tags attached to webbing of the right hind foot to allow individual animals to be identified for recordkeeping. Two commercial diets (proprietary formulas) that are widely used in the industry were fed during the 24-week study. Similar to industry practice, a 56-percent protein diet was fed FIGURE 1. Daily feed consumption, expressed as a percentage of body weight, of American alligator Alligator mississippiensis fed to apparent satiation once or twice per day for 169 days at 30-31 C. FIGURE 2. Weight gain of American alligator Alligator mississippiensis fed to apparent satiation once or twice per day for 169 days at 30-31 C. There was no statistically significant difference between the feeding treatments. FIGURE 3. Length-weight relationship of American alligator Alligator mississippiensis fed to apparent satiation once or twice per day for 169 days at 30-31 C. Among the practical concerns of alligator farmers is overfeeding, which degrades water quality in production houses and increases production cost. Thus, development of a method to determine appropriate feeding rates for alligators of different sizes could be environmentally and economically useful.
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