Rate and Extent of NDF Digestibility of Low-Quality Cool- and Warm-Season Forages

                Forages represent the predominant class of feed within most ruminant livestock operations.  Due to differences in plant variety, stage of maturity, and management practices, forages vary significantly with respect to quality parameters such as digestibility, CP, and palatability.  In addition, many ruminants consume low-quality forages (<7% CP) for extended periods during the annual production cycle.  In an effort to meet the nutritional needs of these animals, supplemental CP is often provided to increase forage OM intake, forage digestibility, and animal performance.

                Forage types can be broadly grouped into cool-season (C3) and warm-season (C4).  Physiological and biochemical differences distinguish C3 (first organic product during carbon fixation is 3-carbon 3-phosphoglycerate) from C4 (first organic product is the 4-carbon oxaloacetate) grasses.  It is generally considered that C3 grasses have a higher nutritional quality than C4 grasses, which has been attributed to higher levels of nonstructural carbohydrates, protein, and water and lower levels of fiber.  Preliminary data suggests that there may be differences in the rate and extent of digestibility of neutral detergent fiber (NDF) in low-quality C3 and C4 forages which contain comparable concentrations of CP and NDF.  This suggests that current CP supplementation strategies and nutritional management plans, primarily developed from C4 data, may not be applicable to low-quality C3 forages.  This research will attempt to further characterize differences in ruminal digestibility of a diverse set of C3 and C4 forages.

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