Effects of Dietary Fish Oil and Green Tea Powder Supplementation on Broiler Chickens Immunity

Background: Poultry strains used by the industry have been submitted to intensive genetic selection for rapid growth and increased effi ciency of feed utilisation along with a high metabolic rate. As major consequences a loss in the immune system competency and increased sensibility to stressors are pointed out. Several nutritional strategies have been essayed to alleviate immuno-suppression in broilers, including the administration of rich 3n- polyunsaturated fatty acids. The purpose of the current study was to investigate the effects of fi sh oil and green tea feeding in broilers chicks humoral immunity using different challenges and the weight of immunity-related organs. Materials, Methods & Results: In the present study, different combinations of fi sh oil (FO) and green tea powder (GrT) supplements were tested in a 3x3 combination of supplement proportions (0%, 1.5% and 2% FO and0%, 1% and 1.5% GrT), in a total of 270 Ross 308 broilers, to analyse the effects of supplementation on the humoral immune response to challenges against Infl uenza and Newcastle virus (antibody titers) and to SRBC (immunoglobulin production) and also in the weight of liver and main lymphoid organs at slaughter. At the end of the study, the carcass weight was similar between groups and to the reported in other studies for the same age at slaughter. On respect to the responses to viral challenges, the GrT supplementation failed to show advantageous effects, compared to FO supplemented groups; when combined with 2% FO the decrease in the humoral response was frequently negatively related to GrT proportions in co-supplementation treatments. However, no signifi cant differences were found between treatment groups. As for the viral challenging, little, non-signifi cant changes were found associated to FO or GrT supplementation. With exception for the group treated with 2% FO plus 1% GrT a slightly non-signifi cant increase in total Igs production was recorded one and 2-weeks after challenging, refl ecting the increase in IgM production. No statistical differences were found between treatments in the unpluck body weight at slaughter, suggesting that no constraints in fed intake were associated with supplementation, in contrast to the reported in some GrT studies. Moreover, little non-signifi cant variations were found in the liver, spleen, thymus or bursa of Fabricius weights. Still, on respect to thymus weight, the supplementation with 1.5% FO signifi cantly improved the relative organ weight, in particular if associated with 1.5% GrT. Also, the bursa of Fabricius weight was signifi cantly increased in groups supplemented of 2% FO plus 1% GrT, compared to all the other treatment groups. Discussion: In the present study, slightly improved humoral responses against infl uenza were found in groups under 2% FO supplementation thought these benefi cial effects could be antagonised by higher GrT co-supplements. Moreover, the humoral response to Newcastle virus challenging was positively infl uenced by FO supplementation and again these effects could be partially reversed by GrT co-supplementation. This is in part supported by the available literature. It has been demonstrated that improvement of humoral responses with fi sh oil are dose dependant, with birds fed with higher levels of FO showing higher antibody titers than those feed medium or low levels. Still, it is also acknowledged that increased FO incorporation rates (above 3 to 4%) in diets result in fi sh fl avours in poultry meat and compromise the consumer acceptance of the product. In conclusion, no detrimental effects were found in association with the supplementation regimens tested, but the irregular responses found with some of the combinations used in the present study need clarifi cation in further studies, with a larger number of birds.