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- Title
Evaluation of fecal near-infrared reflectance spectroscopy profiling technology to predict forage intake estimated using n-alkane markers in grazing cattle.
- Authors
Johnson, J. R.; Carstens, G. E.; Prince, S. D.; Ominski, K. H.; Wittenberg, K. M.; Undi, M.; Forbes, D. A.; Hafla, A. N.; Tolleson, D. R.; Basarab, J. A.
- Abstract
Improved methodology to estimate intake of grazing animals is needed for better-informed management strategies, as current techniques are limited. The objective of this study was to evaluate the accuracy of fecal near-infrared reflectance spectroscopy (NIRS) to predict forage intake estimated using n-alkane markers in grazing animals. Fecal samples were collected from individual animals across 11 trials (n = 260) in which forage DMI was predicted using the alkane-ratio technique. For each trial, fecal samples were collected 2 times daily for 5 consecutive days and composite samples were subjected to NIRS analysis by a Foss NIRS 6500 scanning monochromator (Foss, Eden, Prairie, MN). Fecal spectra were used to develop equations to predict fecal alkane concentration (8 trials; n = 212) and n-alkane predicted DMI (11 trials; n = 260). For the prediction of fecal alkane concentrations, coefficients of determination for calibration (R²c) and cross-validation (R²cv) were 0.90 and 0.87, respectively, for fecal C32 concentration and 0.99 and 0.98, respectively, for fecal C31 concentration. Calibration and cross-validation accuracies (R²c and R²cv) for the prediction of forage DMI estimated using the n-alkane method were 0.90 and 0.87, respectively. These results indicate the presence of strong associations between fecal NIRS spectra and fecal alkane concentrations but do not provide information regarding the robustness of these equations, which is necessary for industry application. To evaluate the robustness of the equations in this study, independent-trial validation was performed. This type of validation was accomplished by removing a single trial from the database and using the remaining 10 trials to develop the calibration equation to predict the independent trial. For this study, independent-trial validation results for the prediction of fecal alkane concentrations and forage DMI estimated using the n-alkane method were poor (R²v < 0.15). Although cross-validation results indicate the potential of this technology to predict forage intake of grazing animals, the independent-trial validation results suggest that a larger database will be needed to enhance robustness of predictive equations across diverse production systems.
- Subjects
ANIMAL droppings; FORAGE; CATTLE
- Publication
Journal of Animal Science, 2017, Vol 95, p55
- ISSN
0021-8812
- Publication type
Abstract
- DOI
10.2527/asasann.2017.112