Abstract
The objective of this experiment was to evaluate the effect of a probiotic (Bacillus subtilis, strain DSM 17299) in broiler diets on feed intake, weight gain, and feed conversion ratio. The experiment included 1,200 male Ross broilers from 1 to 42 days of age. Birds were randomly allocated to 4 treatments, with 10 replicates of 30 birds. The following treatments were applied: T1 - Negative Control (basal diet, with no added growth promoter; T2 - Negative Control + Bacillus subtilis (8 x 10(5) CFUs/g feed); T3 - Negative Control + Bacillus subtilis (3 x 10(5) CFUs/ g de feed) and T4 - Positive Control (avilamycin + anticoccidial from 1 to 35 days of age). At 21, 35, and 42 days of age, there was an increase of antibiotic-free diet intake as compared to the diets with growth promoters (p<0.05), but there was no difference, however, as compared to the diets with probiotic as a growth promoter (p>0.05). The use of growth promoter did not improve weight gain at the studied ages. There was a marked improvement in the feed conversion ratio of broilers fed the diet with antibiotics and of broilers fed the diet with added B. subtilis. It is concluded that the Bacillus subtilis probiotic can be used as a growth promoter in broiler diets.
Highlights
The use of antibiotics as growth promoters has been a common practice in poultry production since the 1950s (Dibner & Richards, 2005)
There was a marked improvement in the feed conversion ratio of broilers fed the diet with antibiotics and of broilers fed the diet with added B. subtilis
Feed intake increased in the treatment group with no growth promoter as compared to the group fed diets containing antibiotic as growth promoter (p
Summary
The use of antibiotics as growth promoters has been a common practice in poultry production since the 1950s (Dibner & Richards, 2005). There are evidences of the presence of antibiotic residues in animal tissues that will be consumed by humans, which may cause resistance of human flora to these groups of antibiotics. Starr & Reynolds (1951) published one of the first reports on antimicrobial resistance caused by the presence of antibiotics in animal products by feeding turkeys with streptomycin. Resistance to tetracycline was shown after its use as growth promoter (Barnes, 1958; Elliott & Barnes, 1959). Kolár et al (2002) described an E. coli strain resistant to 21 of the 23 antibiotics used by the poultry industry
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