Dietary inclusion of 10% Azolla pinnata leaf meal optimises rabbit growth via gut mTOR downstream target p70S6k1 activation and Enterobacteriaceae suppression

Abstract

Abstract

This study evaluated the effects of dietary Azolla leaf meal (ALM) inclusion on the growth performance, caecal fermentation profiles, hepatic oxidative status, intestinal mucosal barrier and gastrointestinal p70S6K1 (ribosomal protein S6 kinase beta-1) the downstream target of rapamycin (mTOR) signalling pathway in growing rabbits. Eighty weaned male V-Line rabbits were blocked by their body weight before random assignment to four dietary groups (n = 20/group): 0% ALM (CON), 10% ALM (AZO10), 20% ALM (AZO20) and 30% ALM (AZO30). The experimental period was 45 d. Growth indices, caecal volatile fatty acids, hepatic antioxidants, histomorphology, mucin histochemistry, intestinal total and phosphorylated p70S6K1 (P-p70S6K1) expression, and gene abundance of selected caecal microbiota were quantified. Feed intake was the lowest in AZO10, and that was associated with an increase in body weight gain, protein efficiency ratio (PER) and relative growth rate (RGR). Most changes in liver metabolites were associated with AZO10 group, including an increase of GSH:GSSG ratio, decreased levels of ATP and 8-hydroxydeoxyguanosine. Inclusion of 30% ALM reduced caecal acetate and the acetate:propionate ratio. Intestinal mucin increased linearly with increasing ALM inclusion. Phosphorylation of intestinal p70S6K1 also increased linearly with increasing ALM inclusion. The abundance of caecal Enterobacteriaceae decreased in rabbits fed ALM. To the best of our knowledge, this is the first study investigating ALM-induced gut p70S6K1 activation and selected microbial abundance shifts in rabbits. In conclusion, inclusion of ALM up to 10% in the rabbit diet may benefit gut and liver health through its impact on p70S6K1, the critical downstream target of mTOR.