Atmospheric ammonia alters lipid metabolism-related genes in the livers of broilers (Gallus gallus)

Atmospheric ammonia in animal housing is reported to have adverse effects on livestock performance and animal health. Previous experiments have found that 75ppm ammonia reduced the production performance and altered body fat distribution quality of broilers. In this study, we examined the body fat distribution, serum metabolites and lipid metabolism gene expression of broiler exposed to ammonia. A total of 400 chickens were randomly allocated to four groups with four replicates and received ammonia treatments at 0, 25, 50 and 75ppm, respectively, for 3weeks. The average daily feed intake and weight gain were decreased when broiler was exposed to ammonia concentration exceeding 50ppm (p<.05). The increased abdominal fat and reduced thickness of subcutaneous adipose were found in broilers of 75ppm group (p<.05). When ammonia exceeded 50ppm, the content of fat in breast muscle of broiler was increased, and when ammonia was higher than 25ppm, the fat in liver was increased (p<.05). It showed that the fat content in liver was a sensitive index for broilers exposed to ammonia. Furthermore, ammonia exposure had no significant effect on total cholesterol and triglyceride in serum, but significantly increased the relative mRNA expression of acetyl-CoA carboxylase (p=.046) and malic enzyme in liver (p=.038), which indicated that ammonia exposure may increase the de novo fat synthesis in liver. In addition, ammonia increased the high-density lipoprotein cholesterol (p=.02) and activity of hepatic lipase in serum (p<.001), which indicated that ammonia exposure may improve the transportation of cholesterol to liver. To conclude, our results indicated that ammonia exposure might increase the de novo fat synthesis in liver and increased the transportation of cholesterol to liver. In addition, the concentration of ammonia in poultry house should be limited lower than 25ppm based on the variation of hepatic fat content.