Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 21, 2006
Publication Date: February 6, 2007
Citation: Coleman, S.W., Bowers, E.J., Riley, D.G., Chase, C.C. 2007. Determination of Alkane Content in Fresh Fecal Samples to Estimate Intake on Pasture [abstract]. American Society of Animal Science Southern Section Meeting. 85(2): Page No. 17.
External markers of wax alkanes C32 and C36 are effective tools for determining intake of grazing animals. The technique requires daily dosing of markers which is impractical under extensive grazing conditions, so controlled release capsules (CRC) have been used. However, consistency of payout from the CRC has been questioned. Also, accepted protocols for alkane analysis employing freeze drying or air drying are time consuming. The objective of this study was to evaluate analysis of fresh feces to determine alkane content and CRC payout. Nine lactating cows and 1 ruminally-fistulated steer grazed a Bahiagrass pasture. The steer and 6 cows were dosed with a CRC that is reported by the manufacturer to release approximately 400 mg each of C32 and C36 daily. Feces were collected daily from the ground for each animal over the next 30 days and divided into two sub-samples, one immediately analyzed for alkanes and the other one was dried (50°C) and analyzed later. External markers were first detected on d 2 in all dosed animals. The last day of elevated concentrations varied from d 13 to d 23 indicating payout was variable among animals on the same diet. Mean C32 and C36 values of dosed animals rose sharply from d 0 (44.1 ppm, 31.9 ppm) to d 3 (117.1 ppm, 108.0 ppm) and remained at those levels until payout ceased. Concentrations of external markers in dosed animals were higher in fresh feces than dry (90.8 vs. 83.1 (P < 0.01) for C32 and 85.1 vs. 76.0 ppm (P< 0.01) for C36). Fecal concentrations of alkanes naturally occurring in plant tissue were 603.5 vs. 600.6 ppm for C33 (P=0.66) and 714.9 vs. 725.0 ppm for C35 (P=0.16) in fresh vs dried samples, respectively. These results indicated that analysis of fresh fecal material was as effective as dry material in determining alkane content. Intake values calculated using constant payout rates for CRCs may be in error due to variable payout, but fresh analysis may facilitate determination of a more accurate payout rate.