Dietary supplementation of a combination of formic acid and sodium formate in practical diets promotes gilthead sea bream (Sparus aurata) gut morphology and disease resistance

Optimizing growth and feed conversion ratios by improving gut function and health is critial to ensuring cost-effective production in aquaculture, especially in the current context of low fishmeal and low fish oil-based diets. However, the use of practical diets based on high levels of plant-based raw materials as an alternative to traditional marine ingredients has been associated with negative effects on fish performance, feed utilization, and health. Organic acids and their salts have been widely used as functional ingredients not only for their antimicrobial and immunomodulatory properties, but also for their potential to promote animal digestive capacity and gut health. The aim of the present study was to evaluate the effects of a mixture of formic acid and sodium formate (Amasil NA®, BASF, Germany- AMA diet) at a dietary level of 0.3%, on key performance indicators, gut morphology and disease resistance to Vibrio anguillarum in juvenile gilthead sea bream (Sparus aurata). The results of the present study showed that fish fed the AMA diet for 8 weeks, performed similar to fish fed the control diet in terms of growth but presented an optimization of 8% in the utilization of a low in fishmeal and high in plant proteins based diet. The AMA-diet also increased the folds length of gilthead sea bream anterior gut, increasing intestinal absorption area, and decreasing the submucosa width and goblet cell size in the posterior gut when included in a high dietary plant protein content diet. Furthermore, dietary supplementation with Amasil NA® at 0.3% increased gilthead sea bream disease resistance against V. anguillarum compared with fish fed the unsupplemented diet. These results highlight the potential of this combination of formic acid and sodium formate based product as a feed efficiency enhancer, and as a gut health promoter in gilthead sea bream plant protein-based diets.