Effects of different dietary protein sources on the growth performance, digestive capacity and amino acid profiles of largemouth bass (Micropterus salmoides) larvae

The successful rearing of largemouth bass (Micropterus salmoides) larvae heavily relies on the development of effective microdiets that enhance domestication success and growth. Herein, a 28-day feeding experiment was conducted to evaluate the effectiveness of different protein sources, namely, fish meal (FM), krill meal (KM) and squid meal (SM), during the weaning phase of largemouth bass larvae, with Artemia (AR) and commercial diet (CD) used as controls. Our results indicated that larvae fed with SM diet exhibited growth outcomes (final body weight [FBW] and specific growth rate [SGR]) second only to those of larvae fed with AR, which was attributed to its higher feed and protein efficiency ratios. No significant difference was observed in the FBW and SGR among the FM, KM and CD groups. In addition, the SM group had a more developed digestive system and higher trypsin activity than the other microdiet groups, although the lipase and amylase activities were not significantly different among the FM, KM and SM groups. The results of amino acid composition indicated that the levels of lysine, arginine and glutamate in the SM and AR groups were significantly higher than those in the other groups, whereas the level of glycine was the highest in the KM group. The expression levels of growth-related genes (insulin-like growth factor 1 (igf-1) and growth hormone (gh)) were markedly higher in the liver and brain of the SM group than in those of the other microdiet groups. In conclusion, our results suggest that SM is the main protein source that can considerably improve the domestication success rate of largemouth bass larvae.