Effect of time of the switch from saturated to unsaturated dietary fat source on the performance of broiler chickens

This experiment was conducted to evaluate the time of the switch from a saturated (tallow) to an unsaturated (sunflower oil) dietary fat source on the performance of broiler chickens. A field experiment was carried out in which seven hundred (Ross hybrid female) broiler chicks were randomly distributed into seven groups with five replicates of 20 birds during a 6 week experiment. The birds were fed ad libitum with isocaloric and isonitrogenous diets containing 5 percent fat (tallow or sunflower oil) for two periods 1-21 and 22-42 days. Tallow was replaced by sunflower oil in the weekly diet of chicks (first treatment six weeks tallow، second treatment 5 weeks tallow followed by one week sunflower oil، and soon to the seventh treatment fed by sunflower oil for the whole six week). Results show that the dietary treatment for 1-21 days period had no significant effect on the body weight (p>0. 05). Further، birds fed diets supplemented with sunflower oil for 22-42 day and the whole period of experiment gained more weight compared to those fed diets supplemented with tallow (p<0. 05). Feed consumption was significantly higher for chicks fed tallow-supplemented diets in 1-21 days period and the whole period of the experiment (p<0. 05). The feed consumption decreased with replacing the type of fat from saturated to unsaturated (p<0. 05). however، in growing period diets had no significant effect on the feed consumption (p>0. 05). Chicks fed sunflower oil diet had the best value for feed conversion ratio (p<0. 05). The highest and the lowest melting points were observed in the first and the 5th-7th treatments، respectively (p<0. 05).