Submitted to: Research Day Abstracts: Regional Universities Research Day
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2002
Publication Date: 10/23/2002
Citation: PEDRO, A., NORTHUP, B.K. 2002. PREDICTING FORAGE QUALITY OF TWO WARM-SEASON GRASSES WITH NEAR INFRARED REFLECTANCE SPECTROSCOPY. RESEARCH DAY ABSTRACTS: REGIONAL UNIVERSITIES RESEARCH DAY. Abstact p. 81-82. Interpretive Summary: Abstract only
Technical Abstract: Forage produced by grasses found in tallgrass prairie is important to many livestock producers in Oklahoma. Quality of these forages changes during the growing season as plants mature and produce greater amounts of cell wall. Rapid, accurate estimates of forage quality could be used to improve grazing management. However, traditional laboratory techniques require significant amounts of equipment and manpower, and results cannot be obtained quickly. This study determined whether useful predictive relationships could be developed between results of traditional laboratory analyses and near infrared reflectance spectroscopy (NIRS), to allow quick descriptions of forage quality. Samples of the grasses big bluestem (Andropogon gerardii) and little bluestem (Schizachyrium scoparium) were collected during March-September 2000 from a tallgrass prairie site in central Oklahoma. These materials were ground to a 2 mm particle size, scanned by NIRS, and analyzed for nitrogen content and in vitro digestible organic matter disappearance(IVDOM). Relationships between reflected wavelengths from NIRS (750-2500 nm range) and amounts of the two characteristics described by wet laboratory analyses were defined by regression techniques. Equations that defined relationships between N content determined by laboratory analyses and NIRS techniques for the two species were both significant (R^2=0.99; P<0.01), and the equations had similar slopes and y-intercepts. Alternatively, equations that defined relationships between laboratory analyses and NIRS-determined IVDOM (R^2 >0.93) were also significant (P<0.01), but the slopes and y-intercepts for the two species differed. These responses indicated that forage quality of these species changed differently over time, particularly during the latter part of the growing season. Also, the strong relationships between the laboratory and NIRS-determined characteristics showed that NIRS could be used to quickly (and accurately) estimate forage quality of these grasses. Such assessments would be useful for improving management decisions, such as those related to supplementation of cattle or timing of grazing. Data from additional years and locations are required to fully test the ability of NIRS to estimate forage quality of these warm-season grasses.