Zinc phosphide residues in gray-tailed voles (Microtus canicaudus) fed fixed particles of a 2% grain bait

This study measured depelted-carcass residues of zinc phosphide (Zn3P2, CAS ı1314-84-7) in 8 (4 and 4♀) gray-tailed voles (Microtus canicaudus). Six (3 3♀) voles were confined individually in 1.89 dkl (5 gal) plastic pails that contained 5, 2% Zn3P2 steam-rolled-oat (SRO) groats; 2 voles (1 and 1♀) served as analytical (unbaited) controls. Four test voles (3 1♀) died within 7.5 h after bait exposure; whereas, 2 test voles showed no signs of toxicosis and were euthanized 7.0 h after bait exposure. Whole carcasses were stored frozen and depelted carcasses were analyzed within 31 days for Zn3P2 residues using a acid-hydrolyzation, gas-chromatographic (GC) method. Analytical controls were euthanized, with carcasses stored and analyzed the same as test voles. A mean (±SD) 4.7 (±0.8) SRO groats were consumed by the test voles; this converted to a mean (±SD) intake of 2.15 (±0.38) mg Zn3P2 and dose of 73.25 mg kg (±22.95) Zn3P2. The mean (±SD) Zn3P2 residue in the 6 test vole carcasses was 0.42 mg (±0.68); control carcasses contained <0.009 mg Zn3P2—20 mg kg) required to affect these species.