Factors affecting the apparent intestinal (small and large) disappearance of dry matter and crude protein from rumen undegradable residues of various feeds determined using the mobile bag technique for cattle

Abstract

This study evaluated the effects of retention time in the post-abomasal digestive tract, washing time (15, 50, 75, 100 s), bag size (3.5 × 5.5 vs. 2.5 × 4.0 cm), sample size to surface area ratio (3.9 vs. 7.5 mg cm-2), pepsin treatment (untreated vs. pepsin-HCl) and bag material (nylon vs. polyester) on apparent dry matter (DM) and crude protein (CP) disappearance from rumen undegradable residues (RUDR) of canola meal, soybean meal, barley straw, barley silage and dehydrated alfalfa using the mobile bag technique. RUDR were placed into 44 or 48 µm mesh size bags and inserted into the duodenum of cannulated steers, with bags recovered in feces. Retention time of bags was not influenced by substrate. Small bags took slightly longer (P < 0.05) to pass through the post-abomasal digestive tract. Retention time in the post-abomasal digestive tract did not affect CP disappearance but had a minor impact on DM disappearance (P < 0.05). Interactions (P < 0.05) were noted between bag size, washing time and substrate. Bag material (nylon vs. polyester) influenced (P < 0.05) CP but not DM disappearance. No effects of pepsin HCl pre-incubation or SS:SA ratio were observed. Polyester may be preferred due to the high N content of nylon. Key words: Cattle, mobile bag technique, nutrient disappearance