[Marker transfer between food particles during digestive transit in the rabbit. Estimation method based on fecal granulometry].

Five adult rabbits (New Zealand White x Californian) were fed ad libitum for 10 days a pelleted feed compound containing dehydrated lucerne whose particles (0.05-0.5 mm in size) were marked with a rare earth, i.e. ytterbium (Yb). In order to estimate the proportion of marker liable to leave its initial site of binding, we measured the amount of ytterbium present on faeces particles larger than 0.5 mm. The total amount of faeces was collected during the following 3 days. The faeces screening technique used in this study was adapted from that applied to feed. However, the repeatability was low for the large particles (greater than 1 mm), whose number was small. Half of the digesta particles (52%) exhibited a smaller size than 0.05 mm. The proportion of large particles (greater than 1 mm) in the faeces was low (1.5%) while that of the other particle classes ranged from 20-33.5%. After pelleting, more than 40% Yb initially bound to lucerne particles measuring 0.5 to 0.05 mm, was present on fine particles (less than 0.05 mm). Accordingly, only minima and maxima amounts of Yb having migrated on large particles (greater than 0.5 mm) could be measured, i.e. 2.5 and 8.9%, respectively of the ingested Yb. Taking also into account a migration towards small particles, about 10% Yb was liable to leave its initial site during its passage through the digestive tract of the rabbit.