Response of juvenile red drum (Sciaenops ocellatus) to practical diets supplemented with medium chain triglycerides

Medium chain triglycerides (MCT), mostly C(6)-C(12), are physiologically active compounds which are readily absorbed, transported and appear to be preferentially utilized as an energy source but are not deposited in lipid stores in a variety of terrestrial animals. Consequently, the incorporation of MCT in feeds may allow the utilization of higher levels of lipids, possibly increasing protein sparing, without affecting the proximate composition of the fish. To evaluate the response of red drum to varying levels of menhaden fish oil (MFO) and MCT's supplements, two growth trials were conducted utilizing a basal diet containing 44% protein and 5.7% lipid. The first growth trial utilized an incomplete factorial design to evaluate the general response of red drum to MCT's and MFO. The final weights and feed utilization of the fish was significantly affected by lipid source and level of supplementation as well as their interaction. In general, final weights of the fish and feed utilization were significantly higher for fish receiving diets supplemented with 0,4 or 8% MFO and lowest in fish offered the basal diets supplemented with 4% MCT. The performance of fish receiving diets supplemented with 8% MCT or a combination of 4% MFO and 4% MCT was intermediate. In the second experiment, low levels of MCT (0-4%) were evaluated in conjunction with low (3%) and high (8%) lipid supplement to the basal diet. Although, not significantly different from the high lipid basal diet, the largest fish and best feed utilization were found in fish offered the high lipid diet containing 1% MCT. However, as the level of MCT supplement was increased performance of the fish in terms of growth and feed utilization was reduced. Increasing the levels of MCT in the diet resulted in a reduction of intraperitoneal fat deposition. The fatty acid profiles of the intraperitoneal fat as well as the polar and neutral lipid fractions from the liver were determined. In general lipid content of the selected tissues reflected the FA profile of the diet. Based on FA profiles of the intraperitoneal fat, it appears that MCT are incorporated into fat stores of red drum. Based on the observed results, the response of red drum to MCT appear similar to other vertebrates but that MCT are incorporated into lipid stores. The incorporation of MCT in diets appears to be a suitable mechanism to reduce excessive lipid deposition in fish; however, with the exception of high lipid diet supplements may result in poor performance of the fish.