| Ruminally cannulated steers were used in a 4 x 4 Latin Square to determine the effect of feed intake level on fiber digestion and other digestion events. Alfalfa haylage, corn silage, and a corn-soybean meal grain mix were incorporated in a 45:20:35 ratio, respectively, DM basis, and fed at either 100, 85, 70, or 55% ad libitum. The fiber fraction provided a larger percentage of digestible DM to total DM digested at low feed intakes than at high. A more rapid rate of cellulose digestion and a slow rate of passage of particulate matter through the rumen and total digestive tract with decreasing feed intake were key factors responsible for bringing about changes in digestion coefficients. The lower tract, accounting for 11-17% of DM disappearance, tended to play a greater role during periods of high feed intake. Waste fiber from dairy cattle, collected with a liquid/solid separator, was evaluated as a roughage source for growing lambs. Fresh dairy waste fiber (DWF) was either mixed with ground alfalfa hay at 0, 10, or 25% (DM) at feeding or ensiled at 0, 25, or 50% (DM) with energy feedstuffs--ground corn, corn silage, corn stalklage, or alfalfa haylage. Increasing DWF decreased DM intakes and decreased digestibilities of DM and nitrogen for all rations except stalklage. Hemicellulose of DWF generally was digested well by lambs fed all rations. Dairy waste fiber was mixed in 1:1 ratios (DM) with either ground alfalfa hay, chopped cornstalks, chopped whole corn plant, or ground corn. Prior to ensiling, mixtures received either no additive, dry cane molasses at 5% of DM, urea at 1% of DM, dry cane molasses at 5% plus urea at 1% of DM, NaOH at 3.3% of DM, or NaOH at 3.3% plus urea at 1% of DM. Effects of these additives on 72 h extent, rate, and lag time of fiber digestion in vitro were measured. Molasses tended to increase digestion rate, especially of hemicellulose. Urea additions resulted in lower extent of digestion of stalklage:DWF and increased rate of hemicellulose digestion of corn silage:DWF. Addition of urea and molasses overcame the depression caused by urea on digestibility of the stalklage:DWF mixture. Sodium hydroxide increased (a) extent of digestion of certain fiber fractions of all silages (except corn silage:DWF), (b) digestion rate of corn silage:DWF and corn:DWF mixtures, and (c) lag time for all feedstuffs except corn:DWF. Urea aided in reducing lag times of alkali-treated roughages. |
