Diets including l-carnitine and varying oil sources regulate liver and testes fatty acids profile and interfere with sperm production in silver catfish (Rhamdia quelen)

This study aimed to evaluate seminal and sperm production, growth, health, and lipid metabolism of male silver catfish (Rhamdia quelen) fed diets containing l-carnitine and varying lipid sources. Herein, males and females (167.33 ± 9.24 g) were both fed across 223 d with eight (08) isoproteic (282 g of digestible protein kg of ration −1) and isoenergetic (13.34 MJ of digestible energy kg of ration −1) diets, containing 0.00, 0.15, 0.45, and 0.75 g l-carnitine kg −1 of feed, soybean, and marine fish oils. Feeding males with diets containing l-carnitine and different oils resulted in an interactive effect (p < 0.05) that improved sperm production. Furthermore, males fed soybean oil and 0.45 g l-carnitine kg −1 had the highest seminal pH and sperm velocities. Fish fed fish oil and 0.75 g l-carnitine kg−1 had the highest gonadosomatic indexes, sperm production, and superoxide dismutase activities recorded in the testes. The testes of these fish also showed increases in docosahexaenoic acid (DHA), polyunsaturated fatty acids (PUFAs), n-3 fatty acids, and higher n-3: n-6 ratios. The individual effect of oils produced viscera with more (p < 0.05) fat, in addition to having higher (p < 0.05) blood levels of albumin, total cholesterol, triglycerides, alongside the lowest level of aspartate aminotransferase in fish fed marine fish oil. The individual effect of l-carnitine also produced muscles with less (p < 0.05) fat, in addition to the highest (p < 0.05) amount of total cholesterol with the lowest amount of high-density lipoprotein (HDL) cholesterol in the blood of fish fed with 0.75 g l-carnitine kg−1. l-carnitine and oils in the diets promoted hepatic and testicular protection whilst regulating lipid metabolism and fatty acid profile in the liver and testes of silver catfish (Rhamdia quelen) males. These benefits led to greater sperm production when fish oil and 0.75 g kg −1 were used, and faster spermatozoa with soybean oil and 0.45 g kg −1.