Evaluation of controlled release devices for administration of chromium sesquioxide using fistulated grazing sheep. 1. Variation in marker concentration in faeces

Abstract

A group of 10 sheep grazed as a single flock; five were dosed with chromium sesquioxide (Cr2O3) using an experimental controlled release device, and five were dosed twice a day with gelatin capsules. Total faecal output was collected from each sheep over a period of 13 days, and in addition, a sample was taken twice daily from the rectum (grab sample). In a second experiment total faeces were collected every 2 h for 24 h. Total faecal output was compared with estimates of faecal output calculated from the quantity of Cr2O3 in the dose, and the concentrations in representative samples and in grab samples of faeces. An examination was made of the biases in the estimates from these two types of samples for the controlled release devices and for the gelatin capsules. Use of the controlled release devices significantly reduced circadian variation in the Cr2O3concentration in faeces, compared with twice daily dosing with gelatin capsules. Consequently variability was lower and biases in estimates of faecal output were relatively small. Once daily grab sampling from sheep with controlled release devices produced more reliable estimates of faecal output than twice daily sampling from sheep with gelatin capsules.