Document Type : Research Paper

Authors

1 Graduate Student of Agriculture & Natural Resources, University of Tehran

2 Associate Professorr, University College of Agriculture & Natural Resources, University of Tehran

3 Professor University College of Agriculture & Natural Resources, University of Tehran

Abstract

The present experiment was conducted to evaluate the effects of different levels of Vitamin
Premix(VP), fed during the last three weeks of a broiler rearing period (22-42 days), on its growth
performance and carcass characteristics. Four hundred 22 day old broilers received diets containing
four levels of supplementary VP (0, 33.33, 66.66 and 100%) each at a different weeks of finisher
period. The diets were formulated as based on wheat and soybean meal, with the experiment
conducted on floor pens of 10 treatments and 4 replicates in a completely randomized design. The
dietary treatments consisted of: T1 no VP supplement during 22 to 42 days of age; Treatments 2, 3
and 4 containing 33.33% VP,. Treatments 5, 6 and 7 with 66.66% of VP supplement and finally
treatments 8, 9 and 10 containing 100% of VPsupplement. The treatmeants were so arranged that T 2,
5 and 8 received only from 22 to 28; treatments 3, 6 and 9 only from 22 to 35, and treatments 4, 7 and
10 only from 22 to 42 days of age. The results finally indicated that VP reduction and withdrawal at 22
days of age did not impair the birds, performance during their last three weeks of rearing period (22 to
42 days). Decrease in the level of VP did not significantly affect the carcass characteristics (carcass
yield, percentages of breast, thigh, liver, heart as wellas abdominal fat).

Keywords