Growth Performance, Biochemical Indices and Antioxidant Status of Grey Mullet (Mugil cephalus Linnaeus, 1758) Under Dietary L-Carnitine Supplementation

L-Carnitine Improves Muscle Nutrient Metabolism and Intestinal Health in High-Fat-Fed Carp (Cyprinus carpio)

L-Carnitine is widely recognized for its involvement in lipid metabolism, but its effects on muscle quality and gut health in carp have not been well studied. The research aimed to investigate how L-carnitine influences muscle quality and intestinal health in high-fat-fed carp. The study was separated into four groups that received either the standard diet, a high-fat diet (HFD), or a HFD supplemented with 500 mg/kg L-carnitine (LLC), or a HFD supplemented with 1000 mg/kg L-carnitine (HLC) for 56 days. L-Carnitine was found to significantly reduce blood lipid levels. In addition, L-carnitine increased the crude protein content and decreased the crude fat content of high-fat-fed carp muscle while improving muscle fiber morphology and muscle quality. L-Carnitine increased the expression of genes related to intestinal tight junction proteins (claudin-2, occludin, and zo-1), improved the expression of genes related to intestinal inflammation, and enhanced the physical barrier function and organization of the intestine. Analysis of intestinal flora and intestinal metabolites showed that L-carnitine increased the diversity of the intestinal flora, increased the abundance of Cetobacterium, and influenced intestinal levels of bile acids, arachidonic acid, and tryptophan-related metabolites. In conclusion, supplementation with 1000 mg/kg L-carnitine improved muscle quality and intestinal health significantly in high-fat-fed carp by regulating muscle nutrient metabolism and intestinal flora.

Suitable ratio of dietary L-carnitine and α-ketoglutarate improves growth and health performance in Nile tilapia, Oreochromis niloticus

L-carnitine (LC) and α-Ketoglutarate (AKG) are important growth promoters used in aquafeed. The study aimed to evaluate the incorporation of LC and AKG at different ratios in the diet of tilapia (initial weight 1.38 ± 0.03 g) in order to facilitate lipid utilization and protein synthesis. Fish were fed six isonitrogenous (~ 30 g/100 g CP) and isolipidic (~ 6 g/100 g CL) diets containing graded LC/AKG ratios of 0 (Control), 0.11, 0.42, 1.00, 2.33 and 9.00 in six treatments for 60 days. Fish fed with LC/AKG ratios 2.33 and 9.00 showed significantly (P < 0.05) higher percentage weight gain, specific growth rate and protein efficiency ratio. Feed conversion ratio in fish-fed diets with LC/AKG ratio 9.00 improved significantly (p < 0.05) than other treatments. The whole-body protein content of tilapia and digestive enzyme activity were significantly higher with higher weight gain. The body lipid content was significantly lower in the LC/AKG ratio 9.00. The liver antioxidant parameters and activity of the immune components were significantly higher in the LC/AKG ratio 9 group. The lower serum triglyceride and cholesterol level was also recorded in LC/AKG ratio 9 group. The histology of the intestine and liver showed increased villi area and decreased lipid droplets, respectively, in tilapia fed with higher LC/AKG ratios. It was concluded from the above results that the higher LC and lower AKG (LC/AKG ratio 9.00) combination attributed maximum lipid utilization and higher protein efficiency and thus better growth performance in tilapia. This was also reflected in activity of digestive enzymes, antioxidant enzymes and immune status in tilapia.