Excretion of chromium sesquioxide and polyethyleneglycol by dairy cows

Abstract

A polyethylene glycol with average molecular weight of 3000-4000 was used as a marker in digestion trials with 6 Ayrshire cows in comparison with Cr2O3. Two rations were fed, consisting of artificially dried grass cut in June and in October. The dried grass was ground and pelleted, with the markers added at the rate of 7.08 [plus or minus] 0.30 g Cr2O3 and 12.54 [plus or minus] 0.10 g polyethylene glycol per 100 g. Over a 5 day trial period recovery of Cr2O3 from the feces averaged 97.2% of amounts consumed, while polyethylene glycol recoveries averaged 96.0% in the June-cut grass ration and only 82.3% for the October-cut grass ration. The variable recoveries of Cr2O3 apparently were due to variations in content of the carrier cubes, but the low recoveries of polyethylene glycol were likely due to artifacts arising during analysis of the feces. Concentrations of Cr2O3 in dry matter of separate defecations varied [plus or minus]10% from the 24 hr. weighted mean, while variations in polyethylene glycol were [plus or minus] 40-60%. Cr2O3 was probably associated mainly with the solid fraction of the digesta and polyethylene glycol with the liquid fraction.