Effect of sampling intervals and digesta markers on abomasal flow determinations.

Four sampling schedules and three digesta markers were investigated with abomasally-cannulated steers. Nonammonia nitrogen flow through the abomasum was used as the criterion for comparison. A single diet, consisting of ground corn cobs and cane molasses and supplemented with soybean meal to 11.5% crude protein, was used. Each steer was fed hourly to maintain a constant digesta flow. Digesta markers used were: polyethylene glycol (PEG) and chromic oxide (Cr2O3), as external markers for the liquid fraction and the particulate fraction, respectively; and indigestible neutral detergent fiber (INDF) and indigestible acid detergent fiber (IADF), as internal markers for the particulate fraction. Treatments were sampling intervals of 24 hr, 48 hr, 48 hr (sampled twice) and 72 hours. Sampling interval did not alter digesta flow through the abomasum. Extending sampling intervals beyond 24 hr or taking more than one sample per day did not appear advantageous. IADF and Cr2O3 appear to be suitable markers for the particulate fraction. However, IADF is an integral part of the particulate fraction and meets the criteria of an ideal marker.