The effects of dietary protein and fiber levels on growth performance, gout occurrence, intestinal microbial communities, and immunoregulation in the gut-kidney axis of goslings

The current study evaluated the effects of dietary protein and fiber levels on growth performance, gout occurrence, intestinal microbial communities, and immunoregulation in the gut-kidney axis of goslings. A completely randomized 2 × 3 factorial design was adopted with 2 CP levels (180 [18CP] and 220 [22CP] g/kg) and 3 crude fiber (CF) levels (30 [low CF], 50 [mid CF], and 70 [high CF] g/kg). The high CP or low CF diets predisposed the goslings to gout. The high protein diets worsened renal function; serum concentrations of UA and Cr as well as XOD activity in 9-day-old goslings fed 22% CP diets were significantly increased. Although CF levels from 3 to 7% did not directly affect kidney health, increasing CF levels might accelerate the increase of probiotics in the cecum of goslings and withhold maleficent bacteria, alleviating the gut dysbiosis caused by high protein diets. An analysis of the cecal microbiota via 16Sr RNA sequencing revealed that the abundance of Enterococcus in the 22CP group was higher than that in the 18CP group but decreased with increasing CF levels on d 9. The abundance of Lactobacillus increased with increasing CF levels. Additionally, higher serum LPS and proinflammatory cytokine concentrations and upregulated mRNA expression levels in the cecal, tonsil, and kidney tissues indicated that high-protein diets could activate the TLR4/MyD88/NFκB pathway and induce both intestinal and renal inflammation in young goslings. Serum LPS concentrations on d 9 were found to decrease with increasing CF, although altering dietary CF levels did not directly affect the serum immune indices of goslings. In conclusion, the high CP diet exerted a negative effect on gout occurrence, microbial communities, and immunoregulation in the gut-kidney axis of goslings, while appropriately increased dietary fiber levels helped maintain intestinal balance and reduced serum LPS concentration. We propose a diet of 18% CP paired with a 5% CF as the optimal combination for gosling feed.