Growth, hepatic health, mucosal barrier status and immunity of juvenile barramundi, Lates calcarifer fed poultry by-product meal supplemented with full-fat or defatted Hermetia illucens larval meal

Abstract

Poultry by-product meal (PBM) as a replacement for fish meal (FM), an expensive and unsustainable protein aquafeed ingredient, has been tested on different aquaculture fish species. However, the complete replacement of FM with a mixture of PBM and Hermetia illucens (HI) larvae in barramundi culture has not been previously investigated. In this study, results are presented on growth performance, fillet fatty acid composition, serum metabolites, skin mucosal barriers, hepatic steatosis, antioxidant activity, and immunity of juvenile barramundi, Lates calcarifer fed either a FM-based diet (0PBM-0HI) or two test diets in which total FM protein was replaced by a mixture of 70% PBM and 30% full-fat (FHI) and defatted HI larvae (DHI) meal (designated as 70PBM-30FHI and 70PBM-30DHI). After 56 days of feeding, the results showed that the growth was affected when fish were fed 70PBM-30DHI with a higher feed conversion ratio (FCR) with respect to 0PBM-0HI and 70PBM-30FHI diets. There was no variation in growth performance, feed utilization, and FCR between 0PBM-0HI and 70PBM-30FHI. The retention of total saturated and monounsaturated fatty acids increased in the fillet of juveniles fed 70PBM-30FHI and 70PBM-30DHI while total retention of polyunsaturated (PUFA), n-3 PUFA, and n-6 PUFA decreased than the control. Serum alanine transaminase (ALT) increased in fish fed 70PBM-30DHI whereas haptoglobin upsurged in 70PBM-30FHI compared to 0PBM-0HI. There were no significant effects in the serum immune response between dietary treatments whilst serum and liver CAT activity were negatively impacted by 70PBM-30DHI. The 70PBM-30DHI induced hepatic steatosis whilst 0PBM-0HI and 70PBM-30FHI showed no obvious change in the liver. Skin mucosal barriers were impacted by 70PBM-30DHI whilst 70PBM-30FHI fed fish showed a similar response to 0PBM-0HI. The fish fed on 70PBM-30DHI showed a higher proportion of infection rate with Vibrio harveyi than 70PBM-30FHI but showed no variation with the control-fed fish. In summary, FHI larvae meal could be a good complementary protein source, particularly when replacing FM completely with insect-based proteins.