EFFECT OF SAMPLING METHOD ON ESTIMATES OF FORAGE QUALITY AND DIGESTIBILITY.

Authors: DILWORTH, CARLA - REDLANDS C.C.; APPEDU, LISA - SWOSU; Brown, Michael; Starks, Patrick; PERKINS, ASHLEY - REDLANDS C.C.; DAWKINS, DAVID - REDLANDS C.C.; BILES, CHARLES - EAST CENTRAL U.

Submitted to: Research Day Abstracts: Regional Universities Research Day
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/2002
Publication Date: 11/1/2002
Citation: DILWORTH, C., APPEDU, L., BROWN, M.A., STARKS, P.J., PERKINS, A., DAWKINS, D., BILES, C. EFFECT OF SAMPLING METHOD ON ESTIMATES OF FORAGE QUALITY AND DIGESTIBILITY. RESEARCH DAY ABSTRACTS: REGIONAL UNIVERSITIES RESEARCH DAY. 2002. Abstract p. 73.

Interpretive Summary: Abstract Only.

Technical Abstract: Forage utilization may be improved by supplementing grazing animals with specific nutrients that are deficient in the forage. Timely identification of nutrient deficiencies in forages can be difficult when done through clip sampling and laboratory analyses. This research at the Grazinglands Research Laboratory studied the potential of using in situ remote sensing to estimate forage nutrients on a real-time basis, as compared to collecting and analyzing random (all grass species from a random quadrat) or selected (bermudagrass only) pasture samples for purposes of formulating supplements for improving lamb gain and forage digestibility. Forages were evaluated in four, 1.6-hectare mixed-plant-specie pastures that were predominantly bermudagrass. Pastures were grazed by 7 to 13 lambs from June 5 to July 31, 2002. Lambs from two pastures received supplements according to remotely-sensed real-time forage quality estimates and average lamb weight; supplements were changed biweekly. No differences in overall lamb gains, forage nutrient quality, or forage digestibility were found between supplemented versus unsupplemented pastures (P > 0.10). Crude protein content declined (P < 0.05) over the grazing season, while changes in fiber content depended on sampling method; remote sensing overestimated (P = 0.02) acid detergent fiber and underestimated (P < 0.001) neutral detergent fiber as compared to samples analyzed in the laboratory. A decline in forage digestibility over time was found when using selected clipped samples but not in random clipped samples (sampling method x time interaction; P < 0.001). Forage digestibility estimated from lamb fecal samples also declined over time, suggesting lambs consumed a diet more similar to selected clipped samples. Results suggest remotely-sensed estimates of forage quality may be more beneficial in guiding supplementation regimens when the remotely-sensed data accounts for selectivity by the grazing animals.