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Journal of Dairy Science Vol. 68 No. 10 2596-2601
© 1985 by American Dairy Science Association ®
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Estimation of Forage Dry Matter Intake in Lactating Dairy Cows Using a Deuterium Oxide Dilution Technique1

J. A. Rogers2

Department of Dairy and Animal Science, The Pennsylvania State University, University Park 16802

W. O. Odwongo and H. R. Conrad

Department of Dairy Science, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691

ABSTRACT

A method for estimating dry matter intake was investigated in dairy cows fed orchardgrass-bluegrass forage. Four Holstein cows in late lactation were confined to tie stalls and fed green chopped forage to verify accuracy of the technique. Intake of dry matter was estimated using equations that described the kinetics of total body water turnover. Total body water and water turnover rate was determined by a single intravenous injection of deuterium oxide (270 mg/kg body weight). Change in concentration of deuterium oxide in the blood was determined by infrared spectrophotometry for 8 d. Total body water was calculated by zero time extrapolation of deuterium oxide concentration time curve using single pool kinetics. Water turnover rate was defined as reciprocal of the slope of the time curve times total body water. Equation used for calculating forage dry matter intake was dry matter intake (kg/d) = percent forage dry matter x [water turnover rate (kg/d) - grain water (kg/d) - drinking water (kg/d) - fecal water (kg/d)]/percent forage water. Fecal water was estimated as 4.435 + .264 x water turnover rate. Intake of dry matter was underestimated by 4.6 to 7.2%.

Actual difference between predicted and measured intake, however, was only .50 to .76 kg/d. Potential exists for this method to determine intake of dry matter of dairy cows grazing forages.

FOOTNOTES

1 Authorized for publication as Paper No. 7102 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

2 Eastman Chemicals Division, Animal Nutrition Supplements, Kingsport, TN 37662.






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Copyright © 1985 by the American Dairy Science Association ®.