Antibiotic growth effect

The committee recommended a comparison of subtherapeutic with therapeutic use of antibiotics on the prevalence of resistant transfer factors in meat animals. Also recommended was a study comparing the enteric flora of vegetarians and meat-eaters. A third study would involve workers in abattoirs and their contacts. These studies are in progress under the direction of Dr. Edward Kass at Harvard University and investigators at the Loma Linda Medical School. The committee also recommended further research on the mechanisms of the antibiotic growth effect. The report (7) said there is little indication that sale of antibiotics, including penicillin and tetracyclines, for feed and veterinary use, "has decreased as a result of the Swann Report."... 

Antibiotic feed additives, antibiotic resistance controversy, 5-6 Antibiotic growth effect characteristics, 113t vs. contamination, 113,1l4t vs. disease level, 1l4-115t Antibiotic residues... 

Antibiotics do not promote growth of sterile, so-called germ-free animals or of chick embryos. This shows that the growth effect is not produced by direct action of antibiotics on animals... 

Conclusions Growth increase approximately 20% by excluding contamination, or by feeding antibiotic. No effect of antibiotic in absence of contamination. 

The growth effect occurs in the presence of resistant intestinal bacteria. One must conclude that in the intestinal tract there are susceptible deleterious bacteria that are Inhibited or eliminated, and also there are harmless intestinal bacteria that become resistant. Upon prolonged use of antibiotics in the same animal colony, it has sometimes been found that the control animals grow more rapidly as time goes by in successive experiments, so that the quantitative growth response becomes less, even though it persists. In other cases ( ), the response has remained about the same. 

Demir E, Sarica, Ozcan MA et al (2003) The use of natural feed additives as alternatives for an antibiotics growth promoter in broiler diets. Br Poult Sd 44(Sl) 44-45 Deresse D (2010) Antibacterial effect of garlic (Allium sativum) on Staphylococcus aureus an in vitro study. Asian J Med Sd 2 62-65... 

Antibiotics (qv) have been fed at subtherapeutic levels to promote mminant animal growth. Possible reasons for the observed growth include decreased activity of microbes having a pathogenic effect on the animal, decreased production of microbial toxins, decreased microbial destmction of essential nutrients, increased vitamin synthesis or synthesis of other growth factors, and increased nutrient absorption because of a thinner intestinal wall... 

Mechanism of Action. The mechanisms by which antibiotic adrninistration at subtherapeutic levels enhance growth rate and efficiency of gain in growing animals have not been clarified. Possible modes of action include disease control, nutrient sparing, and metaboHc effects. There is extensive evidence that the principal benefit from subtherapeutic use of antibiotics results from the control of harmfiil microorganisms. 

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