The effects of increasing the concentration of the mycotoxin, aflatoxin B1 (0, 0.75 or 1.5 mg per kg) on broilers with or without necrotic enteritis or virginiamycin (an antimicrobial growth promoter) were determined by researchers at Amlan International of Chicago and Colorado Quality Research of Wellington in Colorado.

In a paper published in Poultry Science, first author R.L. Cravens and co-authors describe a 23-day study, in which 22 male Cobb 500 chicks per pen were allotted to 12 treatments (3×2×2 factorial arrangement) with eight replications.

Intestines of five birds per pen were examined for lesions on day 21. Birds were allowed to consume feed and water ad libitum. Aflatoxin was included in the diets from day 0. All birds received a 10× dose of coccidiosis vaccine on day 10. Pens of birds where necrotic enteritis was being induced were on litter contaminated with Clostridium perfringens pathogen (CPP) from day 0.

Aflatoxin decreased gain and feed intake and resulted in poorer feed:gain, increased mortality and higher lesion scores.

Inducing necrotic enteritis increased lesion scores and decreased feed intake and gain.

Adding virginiamycin to the diets improved gain, feed intake and feed conversion and decreased mortality.

There was a three-way interaction (aflatoxin × virginiamycin × CPP) on weight gain; increasing aflatoxin decreased gain and the effects of CPP and virginiamycin were dependent on aflatoxin concentration. In the absence of aflatoxin, virginiamycin increased weight gain but was unable to prevent the growth suppression caused by CPP.

At 0.75mg per kg of aflatoxin, virginiamycin no longer increased growth in non-CPP challenged birds but was able to increase growth in CPP-challenged birds. At the 1.5 mg/kg of aflatoxin concentration, virginiamycin increased gain in non-CPP-challenged birds but challenging birds with CPP had no effect on weight gain.

Virginiamycin improved overall feed conversion with the greatest improvement at 1.5mg per kg (aflatoxin × virginiamycin; P<0.05).

Aflatoxin increased lesion scores in unchallenged birds but not in challenged birds (aflatoxin × CPP; P<0.001).

Aflatoxin and necrotic enteritis decrease broiler performance and interact to decrease weight gain, Cravens and co-authors concluded. They added that virginiamycin helps improve gain in challenged birds at 0.75mg per kg of aflatoxin but not at 1.5mg per kg of aflatoxin.

Reference

^{Cravens R.L., G.R. Goss, F. Chi, E.D. De Boer, S.W. Davis, S.M. Hendrix, J.A. Richardson and S.L. Johnston. 2013. The effects of necrotic enteritis, aflatoxin B1, and virginiamycin on growth performance, necrotic enteritis lesion scores, and mortality in young broilers. Poult. Sci. 92(8):1997-2004. doi: 10.3382/ps.2013-03011}

August 2013