PSIII-11 - The effect of feeding supplemental zeolite (clinoptilolite) of two different particle sizes on measures of nitrogen utilization and nutrient digestibility in finishing beef heifers

Clinoptilolite (CLN), could potentially improve nitrogen (N) utilization when fed to beef cattle as it can bind ruminal-ammonia-N (NH₃-N), limiting its loss and subsequent detoxification into urea-N, which is released into blood and is excreted in urine. However, the effectiveness of CLN is influenced by physical properties such as particle size. Although decreasing the particle size has been shown to increase the binding of ammonium in-vitro, this remains to be evaluated in vivo. Therefore, the objective of this study was to determine the effects of feeding CLN of two different particle sizes (30 and 400 µm) on ruminal NH₃-N and plasma-urea-N (PUN) concentrations, ruminal pH, and nutrient intake and apparent total-tract digestibility. Six ruminally-cannulated beef heifers (mean initial BW± SD, 620.8 ± 30.15) were used in a replicated 3 × 3 Latin square design with 21 d periods (sample collection from d 15 to 21). Dietary treatments were: 1) finishing ration with no supplement (CON), 2) CON +30-µm CLN (CL-30), and 3) CON + 400-µm CLN (CL-400). Clinoptilolite was top-dressed (2.5% of diet DM) during morning feeding. Intake was measured daily. Ruminal fluid was collected on d 19 for NH₃-N analysis and blood was collected 3 h post-feeding on d 21 for PUN analysis. Indwelling pH loggers were used to measure ruminal pH (d 15 to 21) and grab fecal samples were collected from d 19 to 21 to determine total-tract nutrient digestibility. Statistical analysis was conducted using PROC MIXED in SAS. There was no treatment effect (P ≥ 0.13) on ruminal NH₃-N and PUN concentrations, ruminal pH, and nutrient (DM, OM, NDF, ADF and CP) intake and apparent total tract digestibility. In conclusion, feeding CLN to finishing heifers had no effect on measures of N utilization, ruminal pH and nutrient intake and apparent total-tract digestibility.