Impact of dietary sorghum inclusion on growth, intestinal microbiome, liver function, and muscle quality in juvenile Nile tilapia (Oreochromis niloticus)

This study examined the effects of varying dietary sorghum levels on growth, intestinal microbiome, liver function, and muscle quality in juvenile Nile tilapia (Oreochromis niloticus). Six diets, each with 300 g/kg crude protein and 17 MJ/kg gross energy, were formulated by twin-screw extrusion technology. These diets included 0 (control), 40, 80, 120, 160, and 200 g/kg sorghum, replacing wheat flour and wheat bran incrementally. A total of 540 healthy juvenile tilapia (7.86 +/- 0.03 g) were randomly allocated to six groups, with each group consisting of three cage replicates (30 fish per replicate) for a 10-week feeding trial. As dietary sorghum inclusion increased, final body weight, weight gain, and protein efficiency ratio initially rose and then declined, peaking at 40 g/kg sorghum level, but it was not different from the other groups. However, sorghum inclusion significantly altered the beta diversity of intestinal microbiome, notably increasing polysaccharide-catabolizing bacteria at 40 g/kg sorghum. When the inclusion level of sorghum in the diet was increased to 80-200 g/kg, there was a notable decrease in the mRNA expression levels of intestinal pro-inflammatory cytokines, including interleukin-1 beta, interleukin-6, interleukin-8, and tumor necrosis factor-alpha-1. At the same time, the mRNA expression level of the intestinal anti-inflammatory cytokine transforming growth factor beta-1 showed an upward trend. The mRNA expression levels of key intestinal tight junction proteins, such as claudin, occludin, and zonula occludens-1, reached their highest point when the sorghum inclusion level was 80 g/kg, after which a downward trend was observed. Similar trends were observed in hepatic phosphofructokinase activity and mRNA expression level. Conversely, hepatic phosphoenolpyruvate carboxykinase activity increased with higher sorghum levels (40-200 g/kg). Hepatic lipid and glycogen contents increased at dietary sorghum levels exceeding 160 g/kg. Improved myofiber development and density were achieved at the 80-120 g/kg dietary sorghum inclusion. In conclusion, optimal physiological outcomes were achieved with 40-80 g/kg dietary sorghum inclusion, without compromising growth performance.