292 Altering the particle size of supplemental zeolite (clinoptilolite): Effects on nitrogen utilization and nutrient digestibility in backgrounding cattle

Abstract

Abstract The objective of this study was to evaluate the effects of feeding supplemental clinoptilolite with a particle size of either 30 microns or 400 microns (US 40 mesh) on measures of nitrogen (N) utilization and nutrient digestibility in backgrounding cattle. Six ruminally cannulated beef heifers were used in a replicated 3 × 3 Latin square design with 21-d periods. The dietary treatments were: 1) a basal forage-based backgrounding TMR with no supplement (CON), 2) CON + 30-micron clinoptilolite (CL-30), and 3) CON + 400-micron clinoptilolite (CL-400). Clinoptilolite was top-dressed (2.5% of diet DM) during morning feeding (1100 h). Ruminal fluid (d 19 at 2, 3, 4, 6 and 12 h post-feeding), spot urine and grab fecal (d 19 at 1400 and 1900; d 20 at 0300, 0700, 1500, and 2300 h; d 21 at 0500 and 1100 h), and blood samples (d 21 at 3 h post-feeding) were collected and analyzed for nutrients and metabolites. There was no diet effect (P = 0.50) on ruminal ammonia-N (NH3-N) and plasma urea-N (PUN) concentrations. Similarly, urine N and urea-N (UUN), and fecal N excretion did not differ (P ≥ 0.28) across diets. There was no diet effect (P ≥ 0.11) on dry matter (DM) and organic matter (OM) intake, and apparent total tract DM, crude protein (CP), and neutral detergent fiber (NDF) digestibility. However, although it did not differ for the CL-400 compared to CON and CL-30 heifers, apparent total tract OM digestibility was greater for CL-30 than CON heifers. In summary, although feeding supplemental clinoptilolite with a particle size of either 30- or 400-microns to beef heifers did not enhance N utilization, apparent total tract OM digestibility was greater for heifers fed supplemental 30-micron but not 400-micron clinoptilolite compared to the CON diet.