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Unique interrelationships between fiber composition, water-soluble carbohydrates, and in vitro gas production for fall-grown oat forages

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Recently, several research projects evaluated the potential of fall-grown oat (Avena sativa L.) for use as emergency fall forage to extend the grazing season, or for routine use as an additional forage production option. Sixty samples of ‘ForagePlus’ oat were selected from a previous plot study for analysis of in vitro gas production (IVGP) on the basis of 2 factors: i) high (N = 29) or low (N = 31) neutral detergent fiber (NDF; 62.7 ± 2.61 and 45.1 ± 3.91%, respectively); and ii) the range of water-soluble carbohydrates (WSC) within the high and low-NDF groups. For the WSC selection factor, concentrations ranged from 4.7 to 13.4% (mean = 7.9 ± 2.06%) and from 3.5 to 19.4% (mean = 9.7 ± 4.57%) within high- and low-NDF forages, respectively. Our objectives were to assess the relationships between IVGP and various agronomic or nutritional characteristics for high and low-NDF fall-oat forages. Cumulative IVGP was fitted to a single-pool nonlinear regression model [Y = MAX × (1 – e (–K × (t – lag)))], where Y = cumulative mL of gas produced, MAX = maximum cumulative mL of gas produced at infinite incubation time, K = rate constant, t = incubation time (h), and lag = the discrete lag time (h). Generally, cumulative IVGP after 12, 24, 36, or 48 h within high-NDF fall-oat forages was negatively correlated with NDF, hemicellulose, lignin, and ash, but positively correlated with WSC, nonfiber carbohydrate (NFC), and total digestible nutrients (TDN). For low-NDF fall-oat forages, IVGP was positively correlated with growth stage, canopy height, WSC, NFC, and TDN; negative correlations were observed with ash and crude protein (CP), but not generally with fiber components. These responses also were reflected in multiple regression analysis for high- and low-NDF forages. After 12, 24, or 36 h of incubation, cumulative IVGP within high-NDF fall-oat forages was explained by complex regression equations utilizing (lignin/NDF)2, lignin/NDF, hemicellulose, lignin, and TDN2 as independent variables (R2 ≥ 0.432). Within low-NDF fall-oat forages, cumulative IVGP at these incubation intervals was explained by positive linear relationships with NFC that also exhibited high coefficients of determination (R2 ≥ 0.749). Gas production was accelerated at early incubation times within low-NDF forages, specifically in response to large pools of WSC that were most likely to be present as forages approached boot stage by late-fall.
W. K. Coblentz , S. E. Nellis , P. C. Hoffman , M. B. Hall , P. J. Weimer , N. M. Esser , M. G. Bertram
USDA Scientist Submission
Journal of dairy science 2013 Nov. v.96 no.11
Elsevier Inc.
Journal Articles, USDA Authors, Peer-Reviewed
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