Iophenoxic and Iopanoic Acid as Bait Markers for Feral Goats

As part of assessments of the palatability of different formulations for baits to be used for the control of feral goats, iopanoic acid and iophenoxic acid were compared as bait markers. After goats ingested iopanoic acid (25, 50, and 100 mg kg-'), peak plasma iodine concentrations (486, 1725, and 1911 pg 100 mL' respectively) were reached after 4 to 8 h, followed by rapid excretion. In contrast, iophenoxic acid (1.5 mg kg-') was more slowly absorbed but remained stable in the plasma at concentrations greater than 240 pg 100 mL-I for three months after ingestion. When goats were fed 10 marked leaves smeared with non-toxic petrolatum containing a total of 50 mg iophenoxic acid, plasma iodine concentrations were proportionally and significantly higher (P<O.001) than in animals fed on marked leaf smeared with non-toxic petrolatum (total of 5 mg iophenoxic acid), indicating a potential for quantifying the amount of bait ingested. Iophenoxic acid, therefore, shows the greatest potential as a bait marker for goats, particularly for quantitative use in palatability and acceptance studies.