Urea for preservation of moist hay

Moist tall fescue (Festuca arundinacea Schreb.) hay was treated with granular urea at rates of between 0 and 220 g urea N kg^-1 dry matter (DM) and baled with a conventional baler. Moisture content (MC) at the onset and end of baling were 400 and 280 g kg^-1, respectively. The hay was stacked in small stacks and stored for 35 days. Fifty-six and 91% of the incorporated urea had been hydrolyzed by 4 and 14 days after baling, respectively. Urea hydrolysis elevated pH and lowered bale temperatures relative to untreated hay. Temperatures in untreated bales were above 50°C for 17 days after baling while treated bales were up to 18°C cooler. Treated hay lost significantly less water during storage than untreated hay. Final MC was significantly related to initial MC and the interaction of urea treatment and initial MC. Total bacterial counts were not significantly changed by urea treatment. Initial populations of yeasts and molds were greater than 10⁵ colony forming units (CFU) g^-1 fresh weight (FW) but were less than 10¹ CFU g^-1 FW after 35 days when another 12 g urea N kg^-1 DM was added. Dry matter of treated hay retained 32% of initial N added as urea after 14 days of storage. Urea significantly improved in vitro dry matter and cell wall digestibilities in samples taken the day of baling and also after 35 days of storage.