Effect of Addition of Varying Amounts of Urea on Preservation of High Moisture Alfalfa Hay

¹ Department of Animal Sciences University of Arizona Tucson 85721
² Department of Animal Sciences University of Arizona Tucson 85721

Experiments were conducted to evaluate the effects of uniformly adding urea (.8, 1.3, 1.5, and 2.6%) to alfalfa hay at baling (Experiment 1) or on the top surface of bales (1 kg per bale or 2.1% of DM) subjected to water and rain damage (Experiment 2). Addition of 1.3% urea to high moisture alfalfa hay (24 to 26%) effectively lowered bale temperatures, nonenzymatic browning, visible mold, and chitin content from those of high moisture, untreated hay. During 5 mo of storage, ADF and NDF in untreated hay increased considerably, but changes were much less when 1.3% urea was added. Urea disappeared rapidly from hays, and, by 36 d after harvest, urea was detectable only at the 2.6% addition. Urea-treated hays, fed as 60% of diet, were eaten readily by late lactation cows; differences were not significant among treatments in DMI, milk yield, milk composition, or digestion coefficients of DM, ADF, and NDF. Urea on the top surface of hay subjected to water damage prevented heating and molding observed in untreated hay. Addition of urea to high moisture alfalfa hay resulted in higher nutritional quality through reduced heating, molding, and lower structural carbohydrate content compared with control, high moisture hay.

Key Words: alfalfa hay • urea addition • high moisture hay • dairy cows

Submitted on June 29, 1992
Accepted on November 30, 1992