عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Poultry requirments for vitamins and minerals are met from two sources feed ingredients and premixes.In practical poultry nutrition, the role of feed ingredients is over looked. This experiment was conducted to evaluate the effects of the time of vitamin and mineral premixes withdrawal on growth and economic performance of broilers. Four hundred and fifty, one day-old male broiler chickens (Ross 308) were used in a completely randomized design with 6 treatments of 5 replicates. Chicks were fed on a common starter diet formulated based on corn and soybean meal, with common vitamin and mineral premix (VMP) levels (0. 25 % each) for the first week. Then, the treatments 1 to 6 were constructed, on the basis of withdrawal time of VMP, in a way that treatment numbers were represented the number of weeks fed on VMP supplemented diet. The results showed that VMP withdrawal from 7, 14 and 21 days of age decreased daily weight gain and feed intake significantly (p<0. 01), and impaired feed efficiency (p<0. 01). While VMP withdrawal from day 28 and day 35, did not influence weight gain, feed intake and feed efficiency. Relative weights of abdominal fat, bursa of fabricius and spleen, and carcass yields were not influenced by VMP withdrawal. The overall results of the present study, considering economical aspects showed that the removal of vitamin and trace mineral supplements from 7 days prior to slaughter can reduce production costs without negative consequences on growth performance of broiler chickens.