Search

Three digestion and two cattle growth studies evaluated ammoniation level or the nutritional value of ammoniated forage relative to nontreated forage plus a molasses-urea supplement. In trial 1, mature limpograss (Hemarthria altissima) was treated with anhydrous ammonia at 0, 2, 3 or 4% of the dry matter (DM), and fed to steers (217 kg) in a digestion trial. Increases (P<.01) in the apparent digestion coefficients of organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF) and hemicellulose (HC) resulting from increased level of ammoniation were significant for the linear contrast. Urea, or cane molasses-urea were added to nontreated limpograss (digestion trial 2, growth trial 1), or rice straw (Oryza sativa, digestion trial 3, growth trial 2) and compared with ammoniated forage (4 g NH3/100 g DM). Growth trials 1 (63 steers, 220 kg) and 2 (54 steers, 277 kg) lasted 94 and 91 d, respectively. Ammoniation increased (P<.05) apparent digestion coefficients of OM, NDF, ADF and HC compared with nontreated forage plus urea or molasses-urea. Steers fed ammoniated forage had improved (P<.05) DM intake (DMI), daily gain (ADG) and gain/feed (G/F) compared with those fed nontreated forage plus urea. Steers fed ammoniated limpograss had similar (P>.05) DMI but improved (P<.05) ADG and G/F compared with those fed limpograss molasses-urea, while steers fed ammoniated rice straw had similar (P>.05) DMI, ADG and G/F compared with those fed rice straw molasses-urea. Molasses-urea addition to nontreated forage resulted in similar (P>.05) OM digestibility, but reduced (P<.05) digestibilities of NDF, ADF and HC compared with nontreated forage plus urea. Steers fed limpograss molasses-urea had increased (P<.05) DMI and ADG, but similar (P>.05) G/F compared with those fed limpograss plus urea; steers fed rice straw molasses-urea had improved (P<.05) DMI, ADG and G/F compared with those fed rice straw plus urea. Ammoniation provides an opportunity for improving the feeding value of low quality tropical forages, and offers an option to traditional winter feeding programs of nontreated forage plus molasses-urea.