Transfer of β-agonists from animal feed into Tricholoma gambosum through manure

Fungi are dependent on animal manure as a cultivation medium and may be vulnerable to feed-derived β-agonist contamination. To test whether β-agonists incorporated in animal feed can transport into fungi through manure, a greenhouse study was conducted with Tricholoma gambosum grown in a culture medium amended with medicated cattle manure. Cattle were orally administrated with a single (ractopamine, 670.0 μg/kg BW/day) or a mixture of β-agonists (clenbuterol, ractopamine, and salbutamol at the doses of 5.3, 223.3, and 50.0 μg/kg BW/day, respectively) for 28 days. Three batches of T. gambosum were harvested. A liquid chromatography tandem mass spectrometry-based method was developed to quantify the number of β-agonists taken up by T. gambosum from animal manure. The analytical recoveries for β-agonists were between 66.61% and 91.78% with relative standard deviations between 1.70% and 12.18%, and the limit of quantification (LOQ) was 0.3 ng/g. The ractopamine residues in T. gambosum from batch 1 were 1.3 ng/g and were below the LOQ in batches 2 and 3 in the single treatment group. In the mixed treatment group, ractopamine concentrations were 0.42 and 0.50 ng/g in batches 1 and 2, respectively, and the salbutamol concentration was 1.94 ng/g in batch 1, while clenbuterol was undetectable in all three batches. These results indicated that the β-agonists transferred to T. gambosum in trace amounts and presented a limited risk to consumers.