Protein and energy relationships in the diet of the American alligator (Alligator mississippiensis).

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.

Essential fatty acid nutrition of the American alligator (Alligator mississippiensis).

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.

Bone morphometrics and tetracycline marking patterns in young growing American alligators (Alligator mississippiensis).

Nine young American alligators (Alligator mississippiensis) were injected at monthly intervals with tetracycline to determine the bone apposition rate and the resorption patterns over a 3-mo period. The periosteal apposition rate increased progressively over the 3-mo period from 2.99 microns/day to 5.94 microns/day. Endosteal apposition rate was much slower with incomplete tetracycline lines being observed on the endosteum. This suggests that most modeling-resorptive activities occur on the endosteal envelope.

Biliary bile acids, bile alcohols, and sterols of Alligator mississippiensis.

Bile from Alligator mississippiensis was found to contain a mixture of more than twenty bile acids, bile alcohols, and neutral sterols. Bile acids and bile alcohols were purified by reversed-phase high performance liquid chromatography and thin-layer chromatography. Concentrations were measured by gas-liquid chromatography on 1% HiEFF-8BP and identifications were made by mass spectrometry. The major neutral sterols consisted of 98% cholesterol and 0.8% cholestanol. Bile acids recovered from the acidic fraction were 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid (61%), 3 alpha, 7 alpha-dihydroxy-5 beta-cholestanoic acid (9%), 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 alpha-cholestanoic acid (8%), and 3-oxo-7 alpha, 12 alpha-dihydroxy-5 beta-cholestanoic acid (10%). Other C27 bile acids identified were: 3 alpha, 12 alpha-dihydroxy-5 beta-cholestanoic acid, 7-oxo-3 alpha, 12 alpha-dihydroxy-5 beta-cholestanoic acid, and 3-oxo-7 alpha, 12 alpha-dihydroxy-5 alpha-cholestanoic acid. Small quantities of C24 cholic, 5 alpha-cholic, chenodeoxycholic, and ursodeoxycholic acids were also detected, as were trace amounts of the C27 bile alcohols 5 alpha-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol, and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25-tetrol. These results suggest that the alligator is acpable of synthesizing both the 5 alpha and 5 beta-isomers of the C27 bile acids. The small amounts of the C24 bile acids present might originate either from C27 bile acid or bile alcohol precursors or from exogenous sources.