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.

Study on the impacts of chemical and green synthesized (Leucas aspera and oxy-cyclodextrin complex) dietary zinc oxide nanoparticles in Nile tilapia (Oreochromis niloticus).

The present study was designed to evaluate the health effects of dietary nanozinc prepared by two methods: conventional chemical method and green method. The parameters evaluated were the extent of bioaccumulation, antioxidant status, histological, immunological changes and DNA damage in Nile tilapia fed nanozinc feed. Zinc oxide nanoparticles were first prepared by green and chemical methods. Before feed preparation, the in vitro antioxidant activity and antibacterial activity of both types of nanoparticle solutions were tested and the results revealed enhanced activities in green synthesized ZnO NP solution. After the acclimatization period, 420 Nile tilapias were distributed randomly into 21 glass tanks with 20 fish per tank in triplicates. Fish were fed control diet without any ZnO NP and (i) GT1-green synthesized ZnO NP diet at 100 mg/kg, (ii) CT1-chemically synthesized ZnO NP diet at 100 mg/kg, (iii) GT2-green synthesized ZnO NP diet at 200 mg/kg, (iv) CT2-chemically synthesized ZnO NP diet at 200 mg/kg, (v) GT3-green synthesized ZnO NP diet at 400 mg/kg and (vi) CT3-chemically synthesized ZnO NP diet at 400 mg/kg for 60 days. After 60 days, gill and liver samples were collected for analysing oxidative stress, histopathological alterations and bioaccumulation of zinc, whereas serum samples were collected for evaluating immune response. The results revealed that the GT3 diet significantly (P < 0.05) enhanced the level of antioxidant enzymes (CAT, SOD, GPx, GR and GSH) than dietary nanozinc prepared by the chemical method. Similarly, the innate immunological parameters were significantly (P < 0.05) augmented in fish fed GT3 diet. Comparative histological study of liver and gill tissues revealed normal architecture in the tissues of fish fed green synthesized NP-enriched feed, whereas the tissues of fish fed chemically synthesized NP feed exhibited histological alterations. Bioaccumulation of zinc was more in the liver followed by the muscle and least in the gills and DNA damage was more evident in fish fed chemically synthesized ZnO NP-enriched feed. In conclusion, the results suggest that the inclusion of 400 mg/kg GT3 diet in fish diet enhanced the level of antioxidant enzymes, boosted immune response and did not cause histological damage to organs, and therefore, GT3 nanofeed can be recommended for fish health improvement.

Modulation of mucosal parameters, innate immunity, growth and resistance against Streptococcus agalactiae by enrichment of Nile tilapia (Oreochromis niloticus) diet with Leucas aspera.

The present study aimed at evaluating the possible effects of Leucas aspera as immunostimulant on mucosal and serum immunity, as well as on growth and resistance against Streptococcus agalactiae infection in Nile tilapia (Oreochromis niloticus) fingerlings. In a 45 days trial, fish were fed experimental diets containing L. aspera 0 g kg-1 (Diet 1- control), 1 g kg-1 (Diet 2), 2 g kg-1(Diet 3), 4 g kg-1 (Diet 4) and 8 g kg-1 (Diet 5). The results revealed a significant increase in the specific growth rate (SGR), weight gain (WG), and final weight (FW) in fish fed diet 3 (2 g kg-1) of L. aspera compared to the control and other supplemented groups (P < 0.05). Also, feeding on diet 3 (2 g kg-1) of L. aspera enriched diet significantly (P < 0.05) increased lysozyme activities in the serum and mucus, serum peroxidase and phagocytosis activity. However, significant (P < 0.05) increase in mucus peroxidase activity was reported in fish fed diet 4 (4 g kg-1) and diet 5 (8 g kg-1) of L. aspera, whereas significantly higher (P < 0.05) alternative complement activity was reported in fish fed diet 2 (1 g kg-1) of L. aspera. At the end of the experiment, nine fish per replication were selected for a challenge test against S. agalactiae. The dietary supplementation of L. aspera significantly reduced the mortality rate and increased the resistance of Nile tilapia following by challenge with S. agalactiae. The highest post challenge survival of 100% was observed in tilapia fed diet 5 (8 g kg-1) following by 92.6% of RPS in fish fed diet 4 (4 g kg-1) and 88.9% in diet 3 (2 g kg-1), 77.8% in diet 2 (1 g kg-1) and 74.1% in diet 1(0 g kg-1).

Protective efficacy of Mucuna pruriens (L.) seed meal enriched diet on growth performance, innate immunity, and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila.

The impact of Mucuna pruriens (L.) seed meal diet on growth performance, innate immune response, and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila is reported for the first time. Infected O. mossambicus was fed with 2 g kg-1, 4 g kg-1, and 6 g kg-1 of M. pruriens seed meal diets significantly increased initial body weight (IBW) and final body weight (FBW) over control, for a period of 4 weeks. At 4 g kg-1 and 6 g kg-1 the enriched diet significantly (P < 0.05) enhanced the survival rate, weight gain (WG), protein efficiency ratio (PER), specific growth rate (SGR), feed conversion ratio (FCR), and feed efficiency (FE) when compared to the control; besides, from weeks 2-4 these diets significantly (P < 0.05) enhanced the complement activity, phagocytic activity, respiratory burst activity, and lysosome activity. On being fed with 4 g kg-1 and 6 g kg-1-enriched diets the cumulative mortality was lower (10% and 12%) than with 2 g kg-1 diet (24%). The present investigation suggests that the enriched diet at 4 g kg-1 and 6 g kg-1 improved the growth performance more than that of the control and negative control; it also positively enhanced the innate immunity and disease resistance against A. hydrophilla in O. mossambicus. Hence M. pruriens can be used as a feed additive to stimulate immunity for effective production of economically valuable freshwater fish, O. mossambicus.