Larry McNease's research while affiliated with University of Georgia and other places

Operational procedures for environmental chambers and methods of handling alligator eggs were tested for three years to determine hatching. success and to evaluate mortality factors. Eggs were collected from nests produced by captive and wild alligators no earlier than three weeks after. laying and as late as five weeks. Hatching success was determined for fourteen variables. The overall hatching rates for artificially incubated alligator eggs were greater than that reported for wild nests. Post hatching mortality was negligible under artificial conditions, averting high losses which occur in pens and especially in the wild.

Design and operational procedures for controlled environmental chambers were tested to determine their effect on growth rates, diseases, and mortality of the American alligator (Alligator mississip-piensis). Alligators were cultured from hatching until 34 months of age. Various diets were tested. Fresh frozen marine fish was preferred due to cost considerations, annual availability, storage quality, animal acceptance, and growth rates. Growth rates and food conversions were determined for a 26 month period. Survival rate was 99.47. for 156 alligators.

1.1. Growth rates and body condition factors for native wild and captive-raised juvenile alligators (Alligator mississippiensis) that had been released to the wild were studied using tag-recapture methods for 274 alligators over a 4-year period. Alligators were grouped by sex, size class, source (farm-released vs native wild) and as to whether they had overwintered or not.2.2. In most groups, the farm-released alligators grew significantly better than wild alligators matched for sex and size; in the remaining groups the post-release alligators grew as well as their counterparts, though not better.3.3. Overwintering tended to slow growth rates in both groups, but farm-released alligators still demonstrated superior growth over native wild alligators even after overwintering.4.4. Males tended to grow faster than females, though this trend was not always significantly greater. In no matched group did females grow faster than males.5.5. Growth rates diminished with increasing size in native wild alligators (smaller alligators grew faster), but growth rates of farm-released alligators remained accelerated even at the larger size classes.6.6. Growth curves were constructed using known recapture data with three growth models (von Bertlanffy, Gompertz and logistic); the calculated maximum attainable length and growth parameters were significantly larger (P < 0.01) for farm-released alligators than wild using all three models.7.7. Body condition factors were not different in captive-raised post-released alligators than native wild alligators.

Alligators reared for 8 weeks on purified diets at 32 °C averaged greater feed intake and body weight gain, but poorer feed efficiency ratios, than those grown at 28 °C. Environmental temperature had no effect on apparent digestibility of protein (95.4%), fat (96.1%), or energy (93.5%). Both isolated soybean protein (40% of dietary protein) and corn dextrin (16% of gross energy) were efficiently digested. High-solubility corn dextrin was slightly, but significantly, more digestible than low-solubility corn dextrin. Protein digestibility was greater when high-solubility corn dextrin was fed. Added taurine (0.1% of diet) improved body weight gain and resulted in greater fat digestibility. In a second experiment, digestibility of dietary protein and fat from purified diets were high (97.3 and 92.8%, respectively) and found to be influenced by dietary fat. Digestibility coefficients for protein, but not fat, were influenced (greater) when feces were allowed to remain in water for up to 6 h prior to collection for digestibility determinations. Digestibility of individual fatty acids varied with fat source. Stearic acid was the least digestible (77%), whereas the apparent digestibility of lauric, eicosenoic and docosapentaenoic acids was the greatest (100%). Fecal collection condition (wet vs dry) influenced the digestibility coefficients of some, but not all, fatty acids.

1.1. Five adult, female alligators (Alligator mississippiensis) were captured at night during the breeding season, and a blood sample taken within 5 min of capture.2.2. The alligators were physically restrained (tied to boards) and additional blood samples taken at 4, 8, 12, 16, 22, 28, 38, and 48 hr after capture. After the last blood sample was collected the animals were released.3.3. Plasma estradiol-17β and corticosterone were measured by radioimmunoassay. Estradiol declined significantly from initial values by 22 hr post capture, but remained unchanged for 48 hr.4.4. Plasma corticosterone rose from a mean of 0.8 ng/ml at capture to 12.6 ng/ml after 4 hr. Corticosterone continued to rise up to 16 hr then declined after 22 hr. From 28 until 48 hr corticosterone again increased significantly.5.5. These results demonstrate that acute stress in female alligators causes significant suppression of plasma estradiol and a biphasic pattern of corticosterone secretion.

1.1. Blood samples were taken from captive and wild adult alligators for evaluation of baseline plasma corticosterone levels. Adult male alligators were found to have significantly higher plasma corticosterone levels than adult female alligators in captive and wild populations.2.2. Captive adult alligators maintained at high stocking densities had plasma corticosterone levels higher than those adult alligators maintained at lower stocking densities, which had lower plasma corticosterone levels comparable to levels found in the wild population.3.3. Higher levels of plasma corticosterone in captive female alligators correlated with lower nesting success.4.4. No differences were noted in plasma corticosterone of adult females actively defending their nests compared to females sampled that were not in nest attendance.5.5. The use of plasma corticosterone levels as an index of stress for monitoring and managing wild and captive commercial populations of alligators is discussed.

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 (DEn) 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.

The essential fatty acid (EFA) nutrition of young American alligators (Alligator mississippiensis) was examined by feeding a variety of fats/oils with potential EFA activity. Over a 12-wk period, alligators fed diets containing 2.5 or 5.0% chicken liver oil grew longer and heavier and converted feed to body mass more efficiently than alligators fed other fat/oil combinations that lacked or contained only trace amounts of arachidonic acid [20:4(n-6)]. Alligators fed an EFA-deficient diet (containing only coconut fat as the dietary fat) were the slowest-growing animals and converted feed to body mass least efficiently. However, over a 41-wk feeding period, alligators fed this diet showed no obvious external signs of deficiency other than being reduced in size and unthrifty. Fatty acid composition of heart, liver, muscle, skin and adipose tissue lipids was influenced markedly by dietary fat composition. Tissues varied significantly in response to dietary fat composition. Heart lipids contained the lowest levels of short- and medium-chain fatty acids and the highest levels of arachidonic acid. Arachidonic acid levels were less influenced by diet than were levels of other 20- and 22-carbon polyunsaturated fatty acids. Radiotracer studies indicated that linoleic acid was converted to arachidonic acid in the liver. Nevertheless, tissue arachidonic acid levels also appeared to be maintained by concentration from dietary sources and selective conservation. It appears that a dietary source of arachidonic acid may be required for a maximum rate of growth.