Use of magnesium ferrite as reference substance to measure passage of food in the gastro-intestinal tract of ruminants

The present work describes the basis and the technique of a direct measurement method for the retention time of food in the forestomachs of sheep. By this method an inert ferrite as powder (MgOFe2O3) is added as a tracer to the food. A small and light magnetometric sensor, encapsulated to withstand the action of physiologic liquids and implanted within the abomasum, detects the presence of small amounts of the tracer at their arrival in the abomasum, as indicated by the appearance of spikes in the recorded pattern. In order to insure that both food and tracer will flow at the same rate, an impregnation method was developed, attaching the tracer material to the tested component of the food. Measurements of time elapsed between giving the marked food and the first appearance of it in the abomasum (retention time) were performed, by continuous monitoring. Retention time could be consistently related to the length of the food particles, as expected. The method has potential applications in other parts along the digestive tract.