Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/1999
Publication Date: N/A
Technical Abstract: Five grain sorghum hybrids grown in 38- and 76-cm rows (high density (HD) and normal density (ND), respectively) were steam-flaked (SF), high-moisture (HM) harvested followed by rolling and ensiling, or dry-rolled (DR). These grains were evaluated in the laboratory to determine the effects of grain sorghum planting density and subsequent processing method on in vitro dry matter disappearance (IVDMD) and pH in a reduced strength buffer (25% McDougall's Buffer Solution and 75% distilled H2O) in vitro system. Treatments were arranged as a 3 x 2 factorial, (three processing methods and two planting densities) blocked by hybrid, and data were analyzed by analysis of variance. Relative to ND, HD planting resulted in lower (P < .10) in vitro ruminal culture pH at 6 h (5.79 vs 5.84), and lower (P < .10) IVDMD at all incubation times except 12 h (37.1, 42.3, 46.4, and 49.1% for HD and 38.5, 42.6, 47.9, and 50.4% for ND at 6, 12, 18, and 24 h, respectively). These differences in IVDMD may have resulted from the lower (P < .001) N content of the HD sorghum relative to the ND (9.7 vs 10.8% CP). Disappearance of dry matter (DM) at 6, 12, 18, and 24 h was least (P < .001) for DR (29.7, 32.6, 37.6, and 41.3%, respectively), and greatest for SF (47.4, 52.7, 56.8, and 57.4%, respectively), followed by HM sorghum (36.2, 42.1, 47.0, and 50.6%, respectively). In vitro ruminal culture pH was least (P < .001) at 6, 12, 18, and 24 h for SF (5.6, 5.0, 4.8, and 4.6, respectively) and greatest (P < .001) for DR (6.1, 5.8, 5.8, and 5.6, respectively), followed by HM sorghum (5.8, 5.5, 5.3, and 5.1, respectively). These data indicate that relative to planting density, processing has a much greater effect on in vitro ruminal DM disappearance and pH.