DIGESTION BY CATTLE OF UREA-TREATED, AMMONIA-TREATED, OR ROLLED HIGH-MOISTURE BARLEY

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Abstract
A study was conducted to compare the feeding value of processed high-moisture barley (HMB) treated by rolling (R-HMB), adding 6% urea (U-HMB), adding 3% anhydrous amonia (A-HMB), or left untreated (W-HMB). After ensiling for at least 42 d, the four treated HMB were fed with timothy hay (1:1 on a dry matter basis) to four ruminally fistulated steers during four time periods in a 4 × 4 Latin square design. During each period, treated HMB was incubated in saccus in the rumen of steers fed the same HMB. Chromium sesquioxide was mixed with the HMB and served as an indigestible fecal marker. HMB dry matter (DM) remaining in bags after incubation was 96.9, 69.3, 91.6 and 95.0% after 12 h and 85.6, 46.9, 67.0 and 50.0% after 36 h incubation for W-HMB, R-HMB, U-HMB and A-HMB, respectively. Disappearance of DM in R-HMB was greater (P < 0.01) than in chemically treated HMB at all time intervals tested. Disappearance of DM in W-HMB was less (P < 0.01) than in chemically treated HMB at incubation times of 8–36 h but was similar at 1 and 4 h incubation. Examination of the barley hulls by scanning electron microscopy indicated that chemical treatment of HMB resulted in greater digestion of the hull, greater growth of bacterial cells, and less production of extracellular polysaccharides than physical treatment (rolling) of HMB. Starch digestibility was greater (P < 0.05) for steers fed R-HMB (86.8%) than for steers fed A-HMB (76.9%) or U-HMB (69.1%). No differences between treatments were observed in DM digestibility. Key words: Cattle, nylon bags, high-moisture barley, electron microscopy, ammonia, processing