This study was conducted to evaluate the effects of n-3 polyunsaturated fatty acids (PUFAs) on reproductive performance in hy-Line W-36 pullet chicks at the onset of laying period. Two hundred eighty-eight 1-day-old pullet chicks with initial BW of 40.73 g were used in a CRD design to a 2 × 2 factorial arrangement. The main effects were 2 sources of n-3 (flaxseed or fish oil) and 2 levels of n-3 (1.5% and 0.5%) in the diet. The concentration of n-6 PUFA was kept constantly (3% of diet) by soybean oil in all experimental phases. During the 5 experimental phases (starter, grower, developer, pre-developer and pre-peak), feed and water were provided ad libitum. Each dietary treatment (fish1.5, fish0.5, flax1.5 and flax0.5) was assigned to 6 replicate cages with 12 newly hatched pullet chicks per cage. The chicks were raised in cages under optimum environmental conditions until 22 wk as recommended by the Hy-line commercial management guide (2007). On wk 15 of experiment, pullets were transferred to the laying house and individually placed in standard laying cages to determine the day of sexual maturity (first oviposition). All birds were photostimulated at 18 wk of ages. The weight of first egg at sexual maturity and 22 wk egg production were numerically decreased in birds fed diet fish1.5 (P > 0.05). However, egg production was affected by the sources (P = 0.005) and levels of n-3 (P = 0.003) of the diet at 21 wk. At the end of wk 18, no significant differences were observed in the BW and FI between sources and levels of n-3 PUFA (P > 0.05). In this study, time of sexual maturity was negatively affected by the sources (P = 0.029) and interaction between main effects (P = 0.03). Laying hens fed fish oil came into oviposition later, after photostimulation according to this: fish1.5; 20d, fish0.05; 14d, flax1.5; 11d and flax0.5; 14d. Our results show that high levels of fish oil delay the time of first oviposition compared with flaxseed.

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