effect of withdrawing vitamin and/or trace mineral premixes from grower and finisher diets of broilers

an experiment was conducted to evaluate the effect of withdrawing vitamin and/or trace mineral premixes from grower and finisher diets of broilers. a 2×4 factorial arrangement of treatments, consisting of four diets and two-removal times (from 28 to 49, and from 35 to 49 days of age) was utilized. the four diets consisted of control, supplemented with vitamin (vit) and trace minerals (tm)(t1); tm with no vit supplements (t2); vit but no tm supplements (t3); neither vit nor tm supplements (t4). average weight gain (wg) and feed intake (fi) were not affected by treatments of 28 to 35 days of age (p>0.05). feed intake for t2 was lower (p>0.05) than for t1 in the 35 to 42 days of age removal time. there were no significant (p>0.05) differences observed between t1 and other treatments for this trait. feed intakes for t1 and t3 were greater (p>0.05) than those for the other treatments during the last week of age. feed efficiency (fe) was greater (p0.05) in comparison with the other treatments. no significant (p>0.05) differences were observed among t1, t2, and t3 for feed efficiency. during the second days of age period weight gain for t2 and t4 were lower (p>0.05) than those for t1 and t3 during the last two weeks of age. fi for t3 was greater (p>0.05) than that for the other treatments during the last week of age, but no significant (p>0.05) differences were observed between t1 and t4. fi for t1 was greater (p