Effects of Feeding Graded Levels of Gelatin Content on Growth, Feed Utilization and Health Status in Head‐Started Leatherback Sea Turtles ( Dermochelys coriacea )

ABSTRACT Leatherback sea turtles ( Dermochelys coriacea ) have been successfully housed in captive conditions for over 1 year while receiving a gelatin‐based artificial diet. However, the levels of gelatin in the feed formulations for this species were not optimized. Here, 2‐month‐old juvenile leatherback sea turtles ( n  = 3 per treatment, 393–394 g initial weight) were given feed formulations containing 2%, 4%, and 6% of gelatin by weight (designated 2G, 4G, and 6G, respectively). Survival, growth, and feed utilization of head‐started leatherback sea turtles were monitored for 8 weeks. Nonlethal techniques were used to assess nutrient availability (fecal digestive enzyme activities and fecal thermal properties) and health status (carapace elemental composition and hematological parameters). No mortality was observed during the feeding trial of leatherback sea turtles. Significant improvements ( p  < 0.05) in growth and feed utilization were observed in the 4G and 6G groups. The quadratic polynomial equation predicts that the levels of dietary gelatin that promote growth and feed utilization were 4.53% ( r  = 0.8774, n  = 9) and 4.77% ( r  = 0.9474, n  = 9), respectively. Turtles in the 4G group had the highest activities of fecal pepsin and lipase ( p  < 0.05) while other digestive enzyme activities were maintained (trypsin, chymotrypsin, and amylase). Also, this group of turtles showed better nutrient bioavailability, as evidenced by the peaks and thermal characteristics observed in thermograms of fecal matter. No adverse effects of dietary gelatin were observed on carapace elemental composition and hematological parameters ( p  > 0.05). Findings from the current report provide a practical feed formulation for head‐starting leatherback sea turtles, and for zoo or aquarium programs.