Effects of a daily dose of zeolite on rumen ammonia of lactating dairy cows consuming fresh-cut ryegrass pasture

Zeolites are aluminosilicates that can be safely fed to ruminants on a daily basis. They have a strong affinity for cations, including ammonium (NH4 +), which creates the potential to adsorb excess ammonium released in the rumen and reduce urinary nitrogen (N) excreted. The main objective of this proof-of-concept study was to evaluate the effect of a single dose of 300 g of zeolite, deposited into the rumens of cannulated dairy cows before the main morning meal of fresh-cut ryegrass pasture, on changes in rumen ammonium concentrations over the following 8 h. The two-week trial was a cross-over design with 12 cows, either fed ryegrass as a sole diet (Control) or with zeolite (Zeolite). There was a consistent trend for rumen ammonium concentrations in the zeolitetreated cows to increase more slowly over time, and were lower than control cows 8 h after the zeolite was given (P = 0.08). This study provides some indications that a daily dose of zeolite, fed at the onset of the morning meal, may have a moderating effect on rumen ammonium concentration, and reduce plasma urea N concentrations in lactating dairy cows fed a ryegrass-dominant diet.