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.

Changes in the proximate and elemental composition of Alitropus typus (Crustacea: Flabellifera: Aegidae) exposed to lethal dose of bacterial consortium.

Alitropus typus is a crustacean parasite, which is increasingly becoming a menace to aquafarmers. In our previous study, a novel microbial consortium comprising of three exoskeleton degrading bacterial strains (Stenotrophomonas maltophilia, Bacillus altitudinis and Klebsiella pneumoniae) had shown promising results as a biocontrol agent for A. typus. The present investigation reports the changes in proximate and elemental composition associated with the application of microbial consortium on the isopod A. typus. Proximate analysis showed an increased level of protein, lipid, and moisture in treated isopod at 48 h compared with untreated isopod. However, ash and chitin concentrations were lower in treated isopod. The elements in the mid-tergite of untreated isopod was compared with the treated isopod at 48 h using scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM-EDAX). The following elements were analyzed in the mid-tergite segment of untreated isopod: C, O, Na, Mg, Al, Si, P, S, Cl, K, Ca and Fe. The results showed that the concentration of calcium had decreased significantly in the treated isopod at 48 h (4.28 ± 0.11%) when compared to the untreated isopod (10.01 ± 0.32%), indicating that the bound form of calcium carbonate in the exoskeleton had been precipitated by microbial action. The concentration of carbon and phosphorous was higher in the treated isopods at 48 h compared to the untreated ones. The data suggests that treatment with microbial consortium is not only an effective but also an environmentally safe alternative for the control of A. typus.

Nutritive value of guar and copra meal after fermentation with yeast Saccharomyces cerevisiae in the diet of Nile tilapia, Oreochromis niloticus.

Solid-state fermentation increases nutritional bioavailability of plant ingredients by reducing the antinutritional factors and complexity of the nutrients. The present experiment was conducted to replace fish meal (FM) with a mixture (3:1) of yeast fermented guar and copra meal (FGCM) in the diet of Nile tilapia. Five iso-nitrogenous (30% CP) and iso-lipidic (6% CL) diets were formulated replacing FM at 0% (FGCM0), 25% (FGCM 1), 50% (FGCM 2), 75% (FGCM 3), and 100% (FGCM 4) with FGCM mixture. Growth, nutrient utilisation, digestibility, digestive enzyme activity, haematological parameters, and antioxidant capacity were analysed in five treatments after a feeding trial of 75 days. Bioprocessing increased the protein and amino acid content and reduced the antinutritional factors in the guar and copra meal. The weight gain was significantly increased in 25% replaced diet. The feed conversion ratio of tilapia fed with FGCM 1 was similar to that of control and significantly lower (P < 0.05) among the treatments. The group fed with FGCM 1 exhibited significantly higher body protein and lipid content. The activity of digestive enzymes and digestibility of nutrients reduced significantly (P < 0.05) with the replacement of fishmeal beyond 25% with the FGCM mixture. Similarly, the antioxidant enzymes and blood parameters were also negatively affected when more than 25% FM was replaced with FGCM mixture. The cubic regression analysis found that 17.45% FM can be replaced with FGCM mixture for optimum weight gain in tilapia.