Assessing the impact of acidifiers on growth performance, innate immune capacity, response to ammonia nitrogen stress, digestive enzyme activity, intestinal histology, and gene expression of Nile tilapia (Oreochromis niloticus).

This study investigated the effects of acidifiers (ACD) supplementation level on the growth, immune response, intestinal histology and gene expression of Nile tilapia (Oreochromis niloticus). The experimental diets included three different levels of ACD concentrations: 0 g/kg (CTRL) as the control, 1 g/kg (ACD1), and 2 g/kg (ACD2). These ACD were sprayed onto the diets and fish were fed to Nile tilapia (7.12 ± 0.47 g) for 56 days. The results indicated that increasing the dietary content of ACD significantly enhanced growth performance, as reflected in higher final body weight, specific growth rate, average daily gain, and feed efficiency. The ACD2 diet showed improved outcomes compared to the CTRL diet. Fish fed ACD diets showed significantly higher antioxidant enzyme activity compared to the CTRL diet and were able to maintain their antioxidant status throughout the experiment. The activity of digestive enzymes, including protease, amylase, and lipase, was significantly increased in fish fed diets supplemented with varying levels of 1 and 2 g/kg diet compared to the CTRL diet (P < 0.05). Additionally, significant increases were observed in the thickness of the intestinal muscularis and the width of the intestinal villi in fish fed ACD at concentrations of 1 and 2 g/kg of the diet, compared to the CTRL diet (P < 0.05). Moreover, dietary supplementation with ACD at concentrations of 2 g/kg of the diet significantly upregulated the expression of immune-related genes (P < 0.05). Overall, the use of ACD in fish diets has shown improvements in growth performance, immune responses, and intestinal histology, indicating their potential as a beneficial feed additive for Nile tilapia aquaculture. To the best of our knowledge, recent evaluations of dietary ACD supplementation in practical diets also highlight the influence of ACD supplementation as a feed additive, which could benefit the aquaculture industry.