Most infection diseases cause serious economic loses to the poultry industry. Recent investigations on the effect of nutrients on immunity are related to the increase in antibody (Ab) responses of the young chickens, which have poor immunity against some diseases even with vaccination. Most of these studies have focused on dietary polyunsaturated fatty acids (PUFAs). The objective of current study was to examine the effects of dietary ratio of n-6 to n-3 on immune and reproduction systems of pullet chicks. Two hundred sixteen Hy-Line W-36 pullet day old chicks were randomly assigned to 3 diets with different n-6 to n-3 ratios of 10, 6 and 2 until 22 wk of ages. The Optomega-50® (Optivite International Ltd, Retford, Nottinghamshire, UK) containing 50% Salmon fish oil was used as a n-3 source. The antibody (Ab) titers for Newcastle Disease (ND), Avian Influenza (AI), Infectious Bronchitis (IB) and Infectious Bursa Disease (IBD) were determined on 4, 6, 10, 14 and 18 weeks of age. The Ab production against AI vaccine was increased by ratio of 10 on weeks 10 and 14 and only increased for ND at 14wk (P<0.05). On the other hand, the Ab response to IBD (14 wk) and IB (14 wk) vaccine were increased at ratios of 6 (P<0.05). The pullets fed diet with n-6 to n-3 ratio of 2, showed lower egg production and late sexual maturity (P>0.05) whereas ovary weight (P=0.01) and number of LYF (P=0.049) were significantly decreased at first oviposition. Our results revealed that, the supplementation of Optomega-50® as a source of n-3 to decrease the ratio of n-6 to n-3 in diet, significantly increased Ab production for ND, IB and IBD in pullet chicks with slight reduction in reproductive organs weight at early production.

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