Ammonia affects production performance and Toll-like receptor mRNA expression of laying ducks

The objective of this study was to assess the effects of different concentrations of ammonia on laying performance and Toll-like receptor (TLR) and cytokine mRNA expression in Shanma ducks. The experiment is a 2 x 3 x 4 three-factor mixed experimental design. The feeding density is 18 ducks per 2.2 square meter (high density) and 12 ducks per 2.2 square meter (low density). The ammonia concentration is 10 ppm, 30 ppm, 50 ppm, and 75 ppm. The ammonia exposure time is 10 D, 20 D, and 30 D. Egg production was higher in ducks exposed to 10 ppm ammonia than in those exposed to 30, 50, or 75 ppm ammonia when they were housed at a density of 12 ducks per 2.2 square meter net. Body weight showed a downward trend as exposure time and ammonia concentrations increased, but there was no significant difference among ducks exposed to different ammonia concentrations for the same amount of time or among ducks exposed to the same ammonia concentration for different lengths of time. The expression of TLR4, TLR5, IL 4, and IL-8 mRNA was significantly lower in ducks exposed to 75 ppm ammonia. These results indicated that ammonia negatively affected duck body weight and egg laying and that TLR4 and TLR5 may be involved in regulating IL-4 and IL-8 during the anti-ammonia stress response in ducks.