title: Unique interrelationships between fiber composition, water-soluble carbohydrates, and in vitro gas production for fall-grown oat forages.
abstract: 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: (1) high (n=29) or low (n=31) neutral detergent fiber (NDF; 62.7±2.61 and 45.1±3.91%, respectively); and (2) 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 gas produced (mL), MAX=maximum cumulative gas produced with infinite incubation time (mL), K=rate constant, t=incubation time (h), and lag=discrete lag time (h). Generally, cumulative IVGP after 12, 24, 36, or 48h 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-grown 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 were also reflected in multiple regression analysis for high- and low-NDF forages. After 12, 24, or 36h 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 TDN(2) as independent variables (R(2)≥0.43). Within low-NDF fall-grown oat forages, cumulative IVGP at these incubation intervals was explained by positive linear relationships with NFC that also exhibited high coefficients of determination (R(2)≥0.75). 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.
authors.affiliation: US Department of Agriculture-Agricultural Research Service, US Dairy Forage Research Center, Marshfield, WI 54449. Electronic address: wayne.coblentz@ars.usda.gov.
authors.forename: W K
authors.initials: WK
authors.lastname: Coblentz
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: S E
authors.initials: SE
authors.lastname: Nellis
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: P C
authors.initials: PC
authors.lastname: Hoffman
authors.affiliation: US Department of Agriculture-Agricultural Research Service, US Dairy Forage Research Center, Madison WI 53706.
authors.forename: M B
authors.initials: MB
authors.lastname: Hall
authors.affiliation: US Department of Agriculture-Agricultural Research Service, US Dairy Forage Research Center, Madison WI 53706.
authors.forename: P J
authors.initials: PJ
authors.lastname: Weimer
authors.affiliation: University of Wisconsin Marshfield Agricultural Research Station, Marshfield 54449.
authors.forename: N M
authors.initials: NM
authors.lastname: Esser
authors.affiliation: University of Wisconsin Arlington Agricultural Research Station, Arlington 53911.
authors.forename: M G
authors.initials: MG
authors.lastname: Bertram
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D018554:Avena / Q000737:chemistry* / Q000254:growth & development*; D001826:Body Fluids / Q000378:metabolism; D002417:Cattle; D004040:Dietary Carbohydrates / Q000032:analysis*; D004043:Dietary Fiber / Q000032:analysis* / Q000378:metabolism; D004063:Digestion; D005260:Female; D005285:Fermentation; D005740:Gases / Q000378:metabolism*; D066298:In Vitro Techniques; D012044:Regression Analysis; D012417:Rumen / Q000378:metabolism; D012621:Seasons; D012995:Solubility; D014867:Water
chemical_list: D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D005740:Gases; D014867:Water
keywords: fiber composition; in vitro gas production; oat; water-soluble carbohydrate