MONOSACCHARIDE DIGESTIBILITY BY DAIRY-COWS FED DIETS HIGH IN CONCENTRATE AND CONTAINING ALFALFA SILAGES

Alfalfa was ensiled by the conventional wilting process or as a mixtur e of 70% fresh alfalfa plus 30% wheat straw treated with SO2. The effe cts of these silages on the digestibility of monosaccharide constituen ts of the TMR by dairy cows was examined. Ten cows in early lactation were divided into two groups of 5 that had similar performance data at the onset of the experiment. Cows were fed for ad libitum intake for 28 d a TMR composed of 70% concentrates, 15% alfalfa hay, and 15% sila ge. The alfalfa silage had lower glucose, xylose, and total carbohydra tes than the silage of alfalfa plus wheat straw treated with SO2. Dige stibilities of DM (70 to 71%), OM (72%), and total carbohydrate (83%) were similar in the two TMR. The digestibilities of NDF carbohydrate f or both TMR were similar. Regardless of treatment, NDF glucose was mor e digestible than NDF xylose and NDF uronic acid and less digestible t han NDF arabinose, galactose, and mannose. The digestibility of total neutral detergent-soluble carbohydrates was 89% in both TMR, but those of neutral detergent-soluble xylose, mannose, and galactose were lowe r than those of neutral detergent-soluble glucose, arabinose, and pect in.