UREA AMMONIATION EFFECTS ON THE FEEDING VALUE OF GUINEAGRASS (PANICUM-MAXIMUM) HAY

Laboratory, digestion, and growth studies evaluated urea as a source o f ammoniation for quality improvement in guineagrass (Panicum maximum) hay. In a laboratory trial, 5.0-kg portions of hay were reconstituted with water to yield final forage moisture concentrations or 25 of 40% and treated with urea at 0, 4, 6, or 8% of tile forage DM, with or wi thout urease addition. Main effects of forage moisture or urease addit ion did not influence (P > .10) CP or NDF concentration or in vitro OM disappearance (IVOMD) of tbe guineagrass hay. Hay CP concentration an d IVOMD increased linearly(P < .01), whereas concentrations of hemicel lulose and ADL decreased Linearly (P < .05) with increasing urea level . In other experiments, round bales of hay (320 kg) were reconstituted with water to yield final forage moisture concentrations of 25 or 40% and treated with urea at 0, 4, or 6% of the forage DM. The urea solut ion was applied as a spray onto the cut edges of the bales, or by low pressure (10 psi) injection. Two- and three-way interactions (P < .05) existed among forage moisture concentration, urea application method, and urea level for CP and NDF concentration and IVOMD of the guineagr ass hay. Greatest enhancements in these forage quality characteristics were obtained when the urea solution was sprayed onto the hay at the 25% forage moisture concentration In two digestion and two growth tria ls, round bales of hay were treated with 0, 4, and 6% urea sprayed ont o the hay at the 25% forage moisture level. In each growth trial, SO S t. Croix White hair castrated male sheep (Trial 1: 34 +/- 5.5 kg, Tria l 2: 17 +/- 3.5 kg) were allotted to six pens of five dead each, resul ting in two pens per treatment. In the digestion trials, six similar s heep were used in a replicated 3 x 3 Latin square design. In the diges tion and growth trials, hay intake increased in a quadratic (P < .05) manner with increasing urea level. Apparent NDF and ADF digestibilitie s increased linearly (P < .05) with increasing urea level. Linear impr ovements in ADG (P < .05) and gain/feed (P < .07); were observed with increasing urea level. Urea ammoniation offers potential for improving the feeding value of tropical forages and provides an option for qual ity forage during the dry season.