Effects of the Time of the Switch from an Unsaturated (Sunflower Oil) to a Saturated (Tallow) Dietary Fat Source on Performance and Carcass Fatty

A total of 700 day old female broiler chicks (Ross 308) were distributed into seven groups in a completely randomized design with five replicates, and 20 chicks in each replicate. Dietary treatments, time of the switch from an unsaturated sunflower oil (SFO) to a saturated tallow (T) dietary fat source, were: 1) SFO for the entire growth period (6 weeks), 2) SFO for 5 weeks followed by T for last week, 3) SFO for first 4 weeks followed by T for last 2 weeks, 4) SFO for first 3 weeks followed by T for last 3 weeks, 5) SFO for first 2 weeks followed by T for last 4 weeks, 6) SFO for first 1 week followed by T for last 5 weeks and 7) T for the entire growth period. Chicks had free access to water and experimental diets during the experimental periods. All diets were calculated to be isocaloric and isonitrogenous. Body weight and feed intake of chicks fed different diets were recorded at 21 and 42 days. At the end of experiment (on 42 day), two birds were randomly selected from each pen and slaughtered and then breast, leg and thigh muscles and abdominal fat were sampled to determine fatty acid profile. The SAS general linear models (GLM) proce-dure was used for the statistical analysis of data. There was statistically significant differences between dietary treatments for body weight, feed intake and feed conversion ratio during the period from 22 to 42 d and the entire growth period, with a higher values of body weight for chicks fed diets supplemented with SFO throughout the entire growth period (P < 0.05). The lower feed conversion ratio was observed in chicks fed T-based diet for the entire growth period. Chicks with more access to T-based diet during the feeding program had significantly higher amounts of saturated and monounsaturated fatty acids in their carcass compared to those fed SFO based diets (P < 0.05). Shifting from SFO to T diet just for a few weeks time was capable in altering the profile of fatty acids in tissues toward a more saturated pattern.