[Accumulation of antibiotics, heavy metals and antimicrobial-resistant bacteria in duck bio-bed]

The objective of this study is to understand the accumulation of antibiotics, metals in the litter, and evolution features of bacterial antimicrobial-resistance during the fermentation of duck bio-bed.

The experiment was conducted in meat duck bio-bed farm of Jiangsu province from November 2011 to July 2013. The new litter and spent litter from 4th, 8th meat duck flock were studied for the accumulation of consumed antimicrobials and metals. Bacterial resistance levels to consumed antimicrobials were measured in the collected litter.

The residues of doxycycline in the litter increased significantly after successive flocks of meat ducks, but ofloxacin had not been detected in all litter samples. The litter for the 8th meat duck flock had the highest level of resistant cultivable bacteria in the three sorts of medium amended with 16 microg/mL, 100 microg/mL doxycycline. Meanwhile, the level of resistant cultivable bacteria in the same sort of medium amended with 8 microg/mL, 50 microg/mL ofloxacin differed insignificantly between different flock litter sample. Different flock litter differed insignificantly in the accumulation content of As, Pb and Hg, and was low in Cd. The 4th, 8th flock litter increased significantly in Zn and Mn than new litter, and increased slowly in Cu and Cr.

With the application of doxycycline in each flock of meat ducks, the content of doxycycline and doxycycline resistance in enterobacteriaceae bacteria in the litter increased significantly, Zn and Mn had an increasing trend overall.