Effects of fulvic acids on gut barrier, microbial composition, fecal ammonia emission, and growth performance in broiler chickens

This study investigated the effects of fulvic acid (FA) on the growth performance, intestinal function, and fecal ammonia excretion of broilers. A total of 480 1-day-old male broilers were randomly divided into 4 treatments: control (CON) treatment, and the treatment on a basal diet supplemented with 0.15, 0.3, or 0.5% FA. The addition of 0.5% FA increased the feed-to-gain ratio and average daily feed intake during the first 7 d of the experiment, whereas, 0.3% FA addition increased the feed-to-gain ratio at 15 to 21 d, but FA addition had no effect on growth performance at other times. Compared to the CON treatment, 0.5% FA addition increased the serum IgA content, amylase, and lipase activities in the jejunum, as well as the lipase activity and mucin 2 content in the ileum. Feeding broilers with 0.15% FA increased the occludin and zonula occluden-1 content in the ileum, elevated intestinal permeability markers such as diamine oxidase, lipopolysaccharide, and D-lactate dehydrogenase, and further enriched functional pathways including nitrogen metabolism and riboflavin metabolism. Also, FA addition (0.15, 0.3, or 0.5%) increased the jejunum mucin 2 content and maintained the relative stability of the cecal microbiota without detrimental changes to the microbiota composition. Importantly, FA addition decreased the fecal ammonia yield on 2, 4, and 5 d of the fecal ammonia determination in a dose-dependent manner and also lowered the urease activity on 1 and 3 d. Therefore, the addition of 0.15% FA was considered the most effective in maintaining the intestinal health and microbial composition of broilers