Autolyzed brewer's yeast enhances growth and intestinal health in early life stages of Nile tilapia (<i>Oreochromis niloticus</i> L.)

Abstract The early life stages of fish are critical for determining the overall productivity and sustainability of aquaculture operations. This study investigated the effects of dietary autolyzed brewer's yeast (ABY) on the growth performance and intestinal health of Nile tilapia fry ( Oreochromis niloticus ). A 35‐day feeding trial with 480 Nile tilapia fry across 12 experimental tanks tested the effects of diets supplemented with 1, 2, and 4 g/kg of ABY, with a control diet for comparison. The results indicated that the diet which had 1 g/kg ABY supplementation (ABY1) significantly enhanced the weight gain and specific growth rate (SGR) while reducing feed conversion ratio (FCR) compared to the control diet. Intestinal gene expression analysis showed significant upregulation of immunoregulatory genes ( tlr2 , il10 , il1β , and igm ), and a tight junction gene ( occludin ) in the ABY1 group. Conversely, tnfα expression was significantly downregulated in the ABY1 and ABY2 groups, indicating a potential anti‐inflammatory effect. Histological analysis of the mid‐intestine revealed healthy morphology with no significant differences in mucosal fold length, muscularis thickness, lamina propria width, and goblet cell count among the treatment groups. The findings demonstrate that supplementing diets with ABY at 1 g/kg level enhances growth performance and modulates the intestinal immune response of Nile tilapia fry, without compromising intestinal integrity. This study offers valuable insights into using ABY as a functional feed additive to enhance Nile tilapia health and development, as well as to promote aquaculture sustainability.