Investigation of the causes for the occurrence of residues of the anticoccidial feed additive nicarbazin in commercial poultry

Investigations were undertaken to identify causes for the occurrence of high levels of the zootechnical feed additive nicarbazin in broiler liver at slaughter. The first investigation on 32 commercial broiler flocks involved sampling and analysis for nicarbazin (as dinitrocarbanilide, DNC) in liver from birds during a 3-10-day period after withdrawal of nicarbazin from their feed and before commercial slaughter. DNC residues in liver samples of broilers scheduled as being withdrawn from nicarbazin for > or =6 days ranged from 20 to >1600 microg kg(-1) (the specified withdrawal period for nicarbazin is 5 days and the Joint Expert Committee on Food Additives (JECFA) maximum residue limit (MRL) is 200 microg kg(-1) liver). Further on-farm investigations on 12 of these flocks, selected on the basis of the feeding system in use and the levels of DNC residues determined in liver, identified issues in feed management contributing to elevated residues in broiler liver. A significant correlation (0.81, p < 0.01, n = 10) between DNC residues in liver samples and in feed samples from the feeding pans was observed. The second investigation on 12 commercial broiler flocks involved sampling and analysis for DNC in liver samples and feed samples from feeding pans and from the feed mill at the three thinnings of birds for commercial slaughter. In the case of one flock, a clear relationship between nicarbazin in feed from the feed mill (10.5 mg kg(-1) DNC), in feed from the feeding pans (6.6 mg kg(-1) DNC) and in liver (583 microg kg(-1) DNC) at first thinning (9 days scheduled withdrawal from nicarbazin) was observed. Such a clear relationship was not observed in other cases, particularly at second and third thinnings, pointing to re-exposure of birds to nicarbazin late in the flock production cycle, probably from the litter. Guidelines outlining best farm practice to eliminate nicarbazin residues in poultry have been published in booklet and poster format for broiler producers and deal with feed system cleaning, feed bin management, feed deliveries, feed usage and records.

Development and validation of a lateral flow device for the detection of nicarbazin contamination in poultry feeds

Concentrations of the coccidiostat nicarbazin as low as 2 mg/kg in feed can result in violative drug residues arising in poultry liver. A lateral flow device (LFD) was developed for the detection of contaminating concentrations of nicarbazin following solvent extraction of poultry feeds. Test results, as determined by both visual and instrumental measurement, are available within minutes. For 22 feed samples, nicarbazin-free and fortified at 2 mg/kg, the % relative inhibition ranged from 0 to 45% and from 53 to 85%, respectively. Nicarbazin contamination at the critical concentration (2 mg/kg) can be determined in all cases providing the sampling is representative. A wide range of feed samples taken at a mill that incorporated nicarbazin into poultry feed were analyzed. Data generated for these samples by both the LFDs and a mass spectrometric method were compared, and a significant correlation was achieved.