Introduction
The cost and availability of protein-rich ingredients is a challenge for the development of the fish feed sector, especially in developing areas. As a result, alternative protein sources are being used, such as brewery spent grains (BSG) and yeast (BSY). As agro-industrial by products, they do not contribute to competition for land and resources with human feed or other animal feed productions. The high-water content (75-85%) of BSG when exiting the brewery limits its use in sub-Saharan Africa due to the heterogenous mastering of drying process in factories. Then, spontaneous fermentation as a low-cost conservation method seems to be an interesting alternative. BSY have been studied most often for their role in boosting immunity. However, their interest as a palatability, attractiveness, or growth enhancer remains little studied. Therefore, these trials aims to determine whether the fermentation state of BSG influences feeding behaviour and growth of shrimp depending on the BSY/BSG ratio.
Material & methods
The behavioural trial aims to study whether feed attractivity and palatability are influenced by the state of fermentation of BSG and by the ratio BSG/BSY following a factorial design described in table 1. 35 shrimp will be distributed in 7, 50L reserve tanks with 5 shrimp per tank. 7 isoproteic experimental feeds containing a neutral base and 15% of BSG and BSY mixture will be manufactured. During 5 days, groups of five shrimp will be presented the different feeds in a tank dedicated to behavioural studies equipped with cameras. Each group is only presented to a feed once a day and is never presented to the same feed twice. Prehension speed, time spent in feeding zone, shrimp activity and feed consumption will be monitored through video tracking (using an AI based model) and statistically analysed.
The growth trial will be conducted over 42 days. 525 juvenile shrimp will be distributed in 35, 50L independent tanks with 15 shrimp per tank. Tanks will be randomly divided into 7 groups with 5 tank per group as described in table 1. The 7 experimental feeds will be isoproteic and isolipidic (36.6% proteins, 7.3% lipids) containing 15% of the BSG and BSY mixtures. At the end of the trial, growth performances will be analysed via statistical analysis.
Objectives
Experiments assessing ingredient attractivity and palatability took place in April 2025. The growth trial started the end of April 2025 and will end in June 2025. These experiments will help to fill the data gap while providing information on the interest of BSG and BSY for aquafeed.