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The objective of this study was to determine the effect of variety and amylopectin content of barley on ruminal fermentation and ammonia-N utilization by mixed ruminal bacteria in vitro. Three barley varieties (WestBred Gustoe, Nebula, Baronesse) and their waxy counterparts were tested. The control grain was corn. All barley varieties were examined at three substitution levels: 25, 50, and 75% with the remaining being corn. Ammonia-N was labeled with 15N-ammonium sulfate. Samples were collected at 0, 2, 4, 6, and 8 h. Barley inclusion enhanced (P<0.05) propionate production and total VFA at the 75% substitution level and, at 8 h, increasing the proportion of barley in the grain mix increased (P<0.05, linear effect) propionate concentration and decreased (P<0.05, linear effect) acetate to propionate ratio. Across sampling points, the waxy variety of WestBred Gustoe resulted in higher (P<0.05) fluid bacteria incorporation of ammonia-N than corn (by 7.6 and 11.9%, 25 and 75% substitution levels, respectively). At the 75% substitution level, waxy barleys resulted in an 8% higher (P<0.01) ammonia-15N incorporation into bacterial N than their non-waxy counterparts. At the end-point of the incubation, barley treatments and waxy barleys had higher (P<0.05) 15N-enrichment of the fluid bacterial N compared with corn and non-waxy barleys, respectively. The combined (fluid- and particle-associated bacteria and protozoa) microbial ammonia-N uptake, however, was not different between corn control and treatments with barley. Results suggest that ruminal responses to barley supplementation may vary depending on its variety and starch composition and differ between fluid- and particle-associated microorganisms. [Copyright &y& Elsevier]

The objectives were to investigate the effect of grain type and a Yucca schidigera extract based product (Grain Prep® surfactant, GP) on ruminal fermentation and ammonia utilization by mixed microbial populations in vitro (Study 1) and ruminal degradation parameters of flaked corn DM and starch in sacco (Study 2). In Study 1, three 8 h incubations were completed with ruminal inoculum from two lactating dairy cows. A GP treated feed mixture, containing alfalfa hay, grain, and soybean meal, was incubated with buffer and ruminal inoculum. The grain part of the feed mixture was either corn (C) or 50:50 corn and high amylopectin barley grain (CB). GP was applied to the feed mix at 0, 60, and 120 ppm (as is basis). At time 0 h, the ammonia pool was labeled with 15N. Inclusion of barley in the grain mixture increased media pH and decreased ammonia concentration (13.0 mM versus 12.7 mM, respectively), but the concentration of total and individual VFA, or incorporation of 15N into bacterial protein, was not affected by grain type, and GP had no effect on ammonia or VFA concentrations. At the incubation end-point (8 h), GP tended (P=0.11) to linearly increase the proportion of bacterial N originating from ammonia N. In Study 2, flaked corn grain produced in a commercial feed preparation facility was treated with GP at 22 ppm (as is basis; GP) or with water (control) and incubated in the rumen of three lactating Holstein cows for 0, 2, 4, 6, 16, 24, 48, and 72 h. Solubility of corn DM and starch increased with GP, compared to the control, by 16 and 18%, respectively. The proportion of potentially degradable DM and starch was reduced, and effective degradability of DM and starch were increased, by GP. A 50% substitution of corn by barley grain had a positive effect on ammonia N utilization in the rumen in vitro. The saponin based surfactant did not affect fermentation or ammonia utilization, but GP treated corn had a higher in sacco degradability of DM and starch in the rumen of lactating dairy cows, mostly due to an increase in the soluble/instantly degradable DM, or starch, with the GP treated corn grain. [Copyright &y& Elsevier]