s.d. sharifi

The effect of omega-3 fatty acids on performance and physical characteristics of eggs in laying hens under physiological stress was evaluated using 96 LSL-Lite layers in a 2 × 3 factorial experiment with two levels of stress (stress and non-stress) and three levels of omega-3 fatty acids (0, 0.24 and 0.48% of diet) in a completely randomized design for 70 days. From age of 35 to 40 weeks, birds were fed with basal diet and various levels of omega-3 fatty acids, at 41 weeks of age. Physiological stress was induced by adding 1.5 mg dexamethasone/kg of diet for one week. Dexamethasone was then removed from the diet and the birds were fed with pre-stressed diets for three weeks (post-stress period). Percentage of production, feed intake, egg mass, as well as physical traits of eggs in stress and post-stress periods were evaluated. During the stress period, the percentage of egg production, weight and egg mass, shell thickness decreased under stress while feed conversion ratio increased (P<0.05). Feed intake of stressed birds fed diets containing different levels of omega-3 fatty acids was lower than other groups (P<0.05). The lowest yolk index was observed in the stressed birds fed diets containing levels of 0.24 and 0.48 % omega-3 fatty acids. In the post-stress period, the egg production, egg mass, feed intake in birds that experienced stress was lower than non-stressed birds and had higher feed conversion ratio (P<0.05). During this period, the shell thickness of the stressed birds receiving level of 0.48% of the omega-3 fatty acids was lower than other groups (P<0.05). In general, the use of omega-3 fatty acids in stressed laying hens with the intensification of reduced feed intake can increase adverse effects of stress on the performance and egg quality.