Effects of dietary p-coumaric acid on the growth performance, digestive enzyme activity, humoral immunity and immune-related gene expression in common carp, Cyprinus carpio

The efficacy of p-coumaric acid (CA) on growth performance, digestive enzyme activity, humoral immunity and immune gene expressions of common carp (Cyprinus carpio) was tested in the present study. Fish were fed diets supplemented with 0, 0.5, 1 and 1.5 g/kg CA for 56 days. According to regression analysis, specific growth rate (SGR), feed conversion ratio (FCR) and weight gain (WG%) were polynomially related to dietary CA levels. The optimum p-coumaric acid supplementation level, based upon these parameters, was 1.35%-1.44%. Furthermore, dietary CA supplementation at levels of 1.0 and 1.5 g/kg significantly improved the serum immune parameters (total Ig, lysozyme and ACH50). Dietary CA especially at 1.0 and 1.5 g/kg increased the intestinal IL-8 and TNF-alpha, while not affecting the expression of IL-1 beta and lysozyme gene. The highest and lowest mortality rates 14 days postchallenge with A. hydrophila were recorded in fish fed control and 1.5 g/kg CA, respectively. In conclusion, the oral administration of CA especially at 1 and 1.5 g/kg inclusion levels has the potential to improve growth performance, digestive enzyme activity and immune responses of common carp.