Interactions and antigen dependence of dietary n-3 and n-6 polyunsaturatedfatty acids on antibody responsiveness in growing layer hens

Effects of four levels of dietary linoleic acid (LA), an n-6 fatty acid, an d four levels of alpha -linolenic acid (LNA), an n-3 fatty acid, and their interactions on immune responses in growing layer hens were studied. Immune responses were induced by injection with keyhole limpet hemocyanin (KLH) o r Mycobacterium butyricum particles at 35 d of age. Antibody (Ab) responses were measured until 21 d after immunization. In addition, delayed-type hyp ersensitivity, lymphocyte proliferation, weekly feed intake, and BW gain we re studied. At Day 7 after immunization, anti-M. butyricum titers in the M. butyricum-immunized hens were decreased by the increase of dietary I,A (P < 0.05). In the period from 10 to 14 d after immunization, anti-KLH Ab tite rs in KLH-immunized animals were affected by the interaction of dietary LA with LNA (P < 0.01). High dietary levels of LA or LNA increased the anti-KL H Ab response. However, at high levels of dietary LA and LNA, anti-KLH Ab t iters were not increased. In the same period, anti-M. butyricum Ab titers o f M. butyricum-immunized hens were affected by the interaction of dietary L A with LNA (P < 0.05). At low levels of LA and LNA, increased LA levels dec reased the Ab response, whereas increased LNA levels at low LA levels hardl y affected the anti-M. butyricum response. At a high level of LA, increased dietary LNA increased the anti-M. butyricum response. in vitro proliferati on of peripheral blood leukocytes after stimulation with concanavalin A (Co nA) was higher in chickens with a high level of dietary LNA. Feed intake de creased when the dietary levels of LA or LNA increased. However, BW gain wa s not affected by dietary treatments. Feed conversion was more efficient in birds fed high levels of LA and LNA. The present study indicates that vari ous factors affect the Ab responses. First, the interaction of n-6 and n-3 polyunsaturated fatty acids (PUFA) is more important than the separate effe cts of n-3 or n-6. Second, the actions of dietary PUFA were different betwe en antigens of a different nature. Third was the nature of the antigen affe cts when dietary PUFA exert their actions and the persistence of these effe cts. The presence of these multiple factors affecting immune responses shou ld be considered when comparing effects of dietary PUFA on immune responses .