Influence of forage species and diet particle size on the passage of digesta and nylon particles from the reticulorumen of steers

Abstract

To assess factors that influence the passage of digesta from the reticulorumen, ruminally fistulated steers (387 kg) were fed to appetite in a 4 x 4 Latin square design either orchardgrass (OG) (Dactylis glomerata L.) or switchgrass (SG) (Panicum virgatum L.) hays. The two hays were fed in either the long form or ground to pass a 2-cm screen. Steers fed OG diets had greater DMI (P < .05) than steers fed SG diets (11.7 vs 10.4 kg/d respectively). Particle size of ruminal digesta and feces determined by wet sieving was greater (P < .05) for the OG and long hay diets than for the SG and ground diets. Particle size of digesta collected from the anterior dorsal sac and anterior ventral sac of the rumen and from the reticulum did not vary (P > .25) with site. Conversely, ruminal concentrations of 1-mm nylon particles tended (P = .11) to be greater in the lower strata of the reticulorumen at 12 and 24 h after dosing. Neither a site effect nor a site x time-after-dosing interaction (P > .75) was observed for the 3- or 5-mm nylon particles, suggesting that a sorting process independent of specific gravity occurs in the rumen for smaller particles (before the reticulomasal orifice). Passage rate of the 1-mm nylon particles from the reticulorumen was greater (P < .01) for animals fed the SG than for those fed the OG diets, whereas for the 5-mm particles, passage rate was greater for the OG diets.(ABSTRACT TRUNCATED AT 250 WORDS)