Ytterbium Binding among Particle Size Fractions of Forage Cell Walls

Abstract

Cell walls from corn silage, orchardgrass silage, chopped alfalfa hay, and alfalfa haylage were used in two experiments to determine the relative binding of ytterbium among forages and sieve size fractions within each forage. In Experiment 1, ytterbium was added at the rate of 1 mg/g cell wall to 4760, 2380, 1190, 600, and <600-μ sieve size fractions of each forage in 30 ml distilled water at 25°C for 48 h. Mean recovery of ytterbium-169 from cell walls of each forage was 56.2, 34.7, 80.3, and 78.4% and for each sieve size across forage was 48.9, 50.5, 66.3, 72.9, and 73.3%. In Experiment 2, cell walls of each forage were incubated as in Experiment 1, then washed with water and acetone and dry sieved using the same screen sizes as in Experiment 1. Recovery of ytterbium-169 was approximately 20 times lower for corn silage and orchardgrass silage than for alfalfa hay and haylage. Mean specific activity for each sieve size was 7858, 5124, 7142, 9156, and 13506 cpm/g cell wall. The increase in specific activity with decreasing sieve size resulted in low estimates of logarithmic mean particle size using accumulative activity as compared to using accumulative weight in a logarithmic normal distribution. Ytterbium should not be used as a marker in experiments of particle size reduction and its use could bias passage rates in experiments of rate of passage. © 1985, American Dairy Science Association. All rights reserved.