Effects of ammonia on growth performance, lipid metabolism and cecal microbial community of rabbits

This study was designed to investigate the effect of ammonia on growth performance, lipid metabolism and intestinal flora of rabbits. A total of 150 female IRA rabbits (35-days-old) were randomly divided into three groups including 0 ppm (CG), 10 ppm (LAC) and 30 ppm ammonia (HAC) groups for a period of 28 days. The average daily weight gain (ADG) of rabbits was significantly reduced in LAC (-17.11%; p < 0.001) and HAC groups (-17.46%; p < 0.001) as compared with the CG. Serum concentration of high density lipoprotein (HDL) and glucose (Glu) were increased in LAC (+80.95%; +45.99; p < 0.05) and HAC groups (+219.05%; +45.89; p < 0.001), while apolipoprotein A1 (apoA1) was decreased in LAC (-58.49%; p < 0.001) and HAC groups (-36.92%; p < 0.001). The structural integrity of cecum was damaged, and the thickness of mucosa and serosa were significantly decreased in LAC and HAC. The acetate, butyrate and propionate level of cecal chyme were reduced in HAC group (-21.67%; -19.82%; -30.81%; p < 0.05). Microbial diversity and burden of Firmicutes were significantly decreased, while that of pathogenic bacteria, such as Bacteroidetes, Clostridium and Proteobacteria were increased in ammonia treated groups. Spearman's correlation confirmed that burden of Ruminococcaceae_NK4A214_group showed significantly negative correlation with acetic acid (r = -0.67; p < 0.001) while Barnesiellaceae_unclassified showed significantly positive correlation with propionic acid (r = 0.50; p < 0.001). In conclusion, ammonia treatment was responsible for an imbalance of intestinal flora, which affected lipid metabolism and damaged intestinal barrier of rabbits, resulting in low growth performance due to lipid metabolism dysfunction.