An experiment was conducted to study the effect of using probiotics,
enzymes . acidifiers ,or antibiotics in broiler diets against negative control ( with no
supplemental growth promoters ) on growth performance and immune response of
Arbor - Acres broiler chicks from 0 - 6 weeks of age. Fifteen thousand (15000) day -
old broiler chicks were randomly divided into five experimental treatment groups with
two replicates each . The different experimental diets were lso-rtutritlve and
contained 21% crude protein and 2950 Kcal ME/Kg feed during the first four weeks
of age ( starter (grower period) and contained 17.5% crude protein and 3000 Kcal
MElKg feed during the last two weeks of age (finisher period) . At the end of starter I grower period, weight gain and feed conversion values
of chicks fed diets supplemented with different growth promoters were approximately
similar to those recorded by chicks fed control diet. At the end of experiment (6
weeks), the values of weight gain, feed conversion, performance Index and carcass
characteristics of birds fed diets containing either probioncs, enzymes. acidifiers or
antibiotics had also no significant differences as compared with those fed the control
diet. The use of these growth promoters reduced the relsolation percentage of E. coli
and proteus organisms from liver and intestine if compared with control group. The geometric mean titre against Newcastle disease virus was highly in birds
which received probiotlcs followed by those having acidifier and enzymes if compared
with other groups.