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Title: External marker administration through an automated head-chamber system provides analogous estimates of fecal output compared to traditional hand feeding

Author
item Gunter, Stacey
item BECK, MATT - Lincoln University - New Zealand
item Moffet, Corey
item REUTER, RYAN - Oklahoma State University

Submitted to: Ruminant Physiology International Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/23/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The objective of this experiment was to determine if titanium dioxide (TiO2) dosed through an automated head-chamber system (AHCS; GreenFeed; C-Lock Inc., Rapid City, South Dakota) is an acceptable way to administer a fecal output marker to cattle grazing. The AHCS used on this experiment has a 2 bin bait feeding system. Bin 1 contained unmarked alfalfa pellets (UMP) and Bin 2 contained alfalfa pellets marked with 1% TiO2 on a dry matter basis (MP). Twelve heifers (body weight = 402 ± 5 kg) were stratified by body weight and then randomized to either 1) dosed with TiO2 by hand (HFD) or 2) dosed with TiO2 through the AHCS (AHCSD) for 19 days. During the morning (0800) all heifers were offered UMP at 0.25% of BW in individual feeding stanchions. The AHCSD heifers received a single dose (32 ± 1.6 g) of MP at their first visit each day to the AHCS system and all subsequent feeding was UMP. The HFD received only UMP during AHCS system visits but received their 32 g of MP during the morning feeding in the stanchions. On day 15, all heifers were dosed with a bolus containing 2.5 g of ytterbium chloride (Yb). Fecal samples were collected via rectal grab every 4 hours for the first 12 hours and then every 12 hours till the end of day 19; concentrations of Yb in feces were fitted to an one-compartment, age-dependent model. There was statistical agreement (P = 0.04) and little difference (P = 0.43) between the HFD and AHCSD methods for the fecal output estimates. However, the among animal variation differed between the 2 dosing methods (standard deviations of 0.1 and 0.7 kg/day, respectively). Increased variability associated with the AHCSD system probably resulted from greater variability in the dose timing because MP were consumed at appetency. There was a lack of agreement between the pulse dosed Yb and Ti fecal output estimates (P = 0.15), but they were also not statistically different (P = 0.30). Bland-Altman analysis showed an acceptable bias (-0.5 kg/day) between Ti and Yb fecal outputs, however, there were wide Limits of Agreement with large 95% confidence intervals, further indicating the lack of agreement between the two dosing methods. Labor savings associated with dosing cattle with indigestible markers through an AHCS may allow more use of the technique; however, caution is recommended due to the increased variability noted in fecal output estimates.