Assessing different sampling regimens for estimating dietary characteristics using internal markers

Objectives: The objectives of this experiment were to optimize fecal sample protocols using internal markers (acid detergent insoluble ash [ADIA], indigestible NDF [INDF] and ADF [IADF]) to estimate DM digestibility (DMD), CP digestibility (CPD), and DE. Materials and Methods: Steers (n = 6; 754 ± 20.5 kg of BW) used in this experiment were housed in individual pens and were fed a starter and finisher diet in 2 periods. Fecal bags were fitted to steers for 4 d during each period. Fecal samples were collected every 12 h for 2 d. The fecal sampling regimens evaluated were (1) one sample collected on one morning (AM-1d); (2) samples collected on 2 mornings (AM-2d); (3) a morning and evening sample collected on 1 d (AM&PM-1d); or (4) a morning and evening sample collected on 2 d (AM&PM-2d). Results and Discussion: The ADIA marker was found to be inadequate under the current experimental and this was largely driven by improvements in precision rather than accuracy. Implications and Applications: Researchers will need to determine whether the improvements in method precision are worth the increased requirements in labor, time, and animal handling. This decision should be driven by experimental design limitations.