CHARACTERIZATION OF LIMESTONES AND THEIR EFFECTS UPON IN VITRO AND IN VIVO ACID NEUTRALIZATION AND UTILIZATION OF FEEDSTUFFS BY CATTLE
Abstract
Capacities of limestones of differing particle size to neutralize acid in vitro and to modify pH and utilization of feedstuffs in vivo were compared. In vitro acid neutralization during pH-stat titrations was faster for fine than coarse limestone. Mixed microbial cultures were more resistant to pH change when they contained fine calcium carbonate. Rations containing 25:75 corn silage:concentrates and 0.95% Ca from either coarse or fine limestone were fed to rumen-fistulated heifers. Dry matter digestibility in polyester bags was higher for the coarse limestone treatment after 16 hr in the rumen (P < .05), but did not differ after 48 hr. Total rumen VFA concentrations were higher (P < .05) for the fine limestone treatment. Rumen volumes, dry matter disappearance and rumen fluid pH and dilution rate did not differ between coarse and fine limestone treatments. Intestinally-cannulated steers were fed rations containing 60% corn silage and 40% concentrates with either 0.35% Ca from a control limestone or 1.05% Ca from coarse or fine limestone. Duodenal and ileal pHs were higher for the limestone treatments. Limestone did not affect rumen pH or total tract dry matter and starch digestibilities, but duodenal and fecal pHs and ruminal dry matter and starch digestibilities tended to increase with increasing level and fineness of limestone. Rumen fluid volume, osmolality, A/P ratios and concentrations of total VFA were unaffected in rumen-fistulated Holstein cows fed 60:40 corn silage:concentrates and either 0.5% Ca (Control) or 1.0% Ca from either coarse or fine limestone. Rumen pH increased (P < .05) with limestone supplementation. Fecal pH tended to increase (P > .05) and fecal starch percentage decreased (P < .05) with increasing level and fineness of limestone. Ruminal fluid dilution and particulate turnover rates were slower (P < .05) for the coarse limestone than the control treatment. Differences between coarse and fine limestones noted in vitro were observed under some conditions in vivo, but they were not consistent for all experiments.
Degree
Ph.D.
Subject Area
Livestock
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