Abstract
Three tetracycline compounds, demeclocycline hydrochloride (DMCH), tetracycline hydrochloride (TCH), and chlortetracycline hydrochloride (CTH), were administered by gavage and tested as fluorescent bone markers for adult cotton (Sigmodon hispidus) and roof (Rattus rattus) rats. Probit and logistic regression models did not fit the data well; a more extensive test, with more widely spaced doses and additional low doses, may improve fit. TCH and CTH, which are considerably less expensive than DMCH, appeared to be similar to DMCH in marking roof rats at higher doses (72, 108, and 162 mg/kg) but not at low doses (32 and 48 mg/kg). Cotton rat mandibles were not as distinctly marked as those of roof rats by any of the compounds. Only at high doses (162 and 243 mg/kg) of DMCH or TCH were more than 50% of cotton rats scored as marked by both evaluators. The dose-response test results support field evidence that DMCH is not an effective marker for cotton rats. Neither TCH or CTH appear to be better candidates than DMCH as markers for cotton rats.
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