Effects of different dietary oil sources on immune function in cyclophosphamide immunosuppressed chickens

An experiment with 3 x 2 factorial arrangement was carried out to determine the effects of dietary supplementation with different dietary oil sources on immune function in cyclophosphamide (CY) immunosuppressed chickens. Three hundred and sixty day old male Arbor Acre broiler chickens were randomly allocated into six treatments. The main factors consisted of dietary supplemental oil sources (45 g fish oil, maize oil or poultry oil per kilogram of diet) and immunosuppressive challenge (birds challenged with CY or treated with sterile saline). Growth performance, the relative weights of the spleen, thymus and bursa, antibody production, lysozyme activity and prostaglandin E-2 (PGE(2)) synthesis were investigated. The fish oil diets resulted in higher body weight gain, feed efficiency, lysozyme activity, anti-bovine serum albumin (BSA) and anti-NDV titers than the maize oil or poultry oil diets (P<0.05) in different growth periods. Chickens treated with CY showed significant decrease (P<0.05) in growth performance, the relative lymphoid organs' weight, lysozyme activity, antibody response to BSA and NDV when compared to the saline-treated control chickens. The interaction of oil source with CY on body weight gain, feed intake and anti-NDV titers was observed across different growth periods, i.e. fish oil attenuated the growth-suppressive and immunosuppressive effects of CY treatment. The effect of oil source was significant on the production of PGE(2) (P<0.05), and the lowest level of PGE(2) production was in fish oil (FO) fed chickens and the highest level was in maize oil (MO) fed chickens independent of CY treatment. The negative correlations were found between PGE(2) synthesis and lysozyme activity in serum at the age of 28 d (R-2=-0.686, P<0.001), but no correlation was observed between PGE(2) synthesis and antibody titers. The results suggest that dietary n - 3 polyunsaturated fatty acids (PUFAs) supplementation enhanced the humoral immune response under not only the normal physiological status but also the immunosuppressive status, and the overall effects of fish oil on humoral immunity cannot be accounted for solely on the basis of PGE(2)-mediated effects. (C) 2007 Elsevier B.V. All rights reserved.