Yeast hydrolysate (YH) have gained increasing interest in animal nutrition as non-conventional raw material presenting a high proportion of highly digestible, quickly absorbed proteins (free AA , small peptides) in addition to fermentable carbohydrates. Thus, feed formulation with YH may allow to optimise the feed performance and functional benefits while reducing reliance on marine or land-based ingredients such as soybean meal due to high digestible protein content.
A 10-week trial used juveniles gilthead seabream (25g; 20 fish/tank ) under optimum rearing conditions within 12 * 150 L tank s connected to a fully controlled RA S supplied with natural seawater ( 29 ppt; 22°C). The trial tested 3 diets in quadruplicate tanks. The control diet was formulated to the species life-stage requirement s according to standard industry practices (45% plant- ingredients; 20% land-anima l meal, 20% fish-meal (FM) , 9.6 % fish-oil ; 48% crude protein ; 14.5 % crude lipids). The second experimental diet (YH-Iso) was formulated by reducing FM by 10% , adding 2% YH and balancing the other ingredients to achieve an iso-protein, -lipidic and -energy levels . The third experimental diet (YH-LowP ) had the same FM and YH inclusion as the second diet but with 1% reduced total crude protein content (47% protein) to evaluate the performance of high digestible protein of YH. Small inclusion of DL-methionine in all experimental diets was necessary to balance the low methionine content of YH. Extruded f eeds were hand-fed at a fixed ration. Statistical differences were assessed by 1-way or 1-way nested ANOVA and Tukey’s post-hoc test , significance was accepted at P < 0.05.
Over the trial’s duration, growth was significantly higher in the YH-i so compared to the Control which was associated with a numerical improvement in FCR (-5.1% ) and a slight increase in feed intake. In comparison, the re was no significant difference in growth and feed performance between the control and YH-LowP diets . Liver transcriptomic , gut histology and microbiota data will shed light on how YH may bring the production benefits measured .
In conclusion , incorporating 2% YH within balanced formulation has the potential to improve the nutritional performance and sustainability of gilthead seabream production . This may represent a valuable option in the context of increasing pressure on conventional raw material.