Brewer’s spent grains (BSGs) as feedstuff for striped catfish, Pangasianodon hypophthalmusfingerlings: An approach to transform waste into wealth

Abstract

The surging demand for conventional fish feed ingredients resulted in rising cost of fish feed, which is considered as a limiting factor for the expansion of aquaculture industry. There is need of alternative protein sources, especially those are by-products, and not suitable for human consumption and having the environmental concern of their safe disposal such as brewer’s spent grains (BSG). An experiment was conducted to assess the effect of substitution of soybean meal with brewer’s spent grains on growth, survival, nutrient utilization efficiency in Pangasianodon hypophthalmus fingerlings. Five iso-nitrogenous (365 g protein. kg−1 diet) and iso-caloric (20.44 MJ kg−1) experimental diets were formulated with different graded level of brewer’s spent grains like 0%, 25%, 50%, 75% or 100% in replacement for soybean meal and designated as control, T1, T2, T3, T4 respectively. The BSG contributed 0%, 24.26%, 47.10%, 69.51 and 91.26% of the total protein in the diets. Each diet was randomly assigned to 15 experimental tanks containing 20 fish in triplicates and fed to satiation twice daily at 09:00 h and 17:00 h. At the end of the feeding trial, weight gain percentage (WG%), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER) and apparent net protein utilization (ANPU) parameters were found significantly (p < 0.5) higher at 50% brewery waste level but also found non-significant with control and 25% brewery waste level fed group. Fat retention, body indices, and survival rate were found non-significant (p > 0.5) among different dietary treatments. Significantly higher moisture content (p < 0.5) was recorded in fish fed with 0% dietary BSG group (control). Maximum crude protein content was found to be significantly higher (p > 0.05) in fish fed with 50% BSG level compared to the other BSG fed groups. Total ash and ether extract content did not change within treatment groups. Overall, this study suggests that brewer’s spent grains can serve as an alternate protein source with 50% level substitution of soybean meal without any adverse effect on growth, nutrient utilization and feed conversion. The finding could help in reducing the environmental concern of disposal of an agro-industrial waste by transforming a waste in the feed for commercially important fish species of aquaculture.