Location: Livestock Nutrient Management ResearchTitle: Technical note: using an automated head chamber system to administer an external marker to estimate fecal output by grazing beef cattle
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2021
Publication Date: 8/12/2021
Citation: Beck, M.R., Gunter, S.A., Moffet, C., Reuter, R. 2021. Technical note: using an automated head chamber system to administer an external marker to estimate fecal output by grazing beef cattle. Journal of Animal Science. Article skab241. https://doi.org/10.1093/jas/skab241.
Interpretive Summary: Methane emission by grazing cattle accounts for over three quarters of all cattle produced methane and is a powerful greenhouse gas. Herbage intake by grazing cattle needs to be measured to more accurately assess and subsequently mitigate this methane source. However, the current methods used to measure intake by grazing cattle are labor intensive, require daily restraint of the cattle, and disrupts grazing times behavior. So, scientists from ARS (Bushland Texas and Woodward, OK) and Oklahoma State University tested the accuracy of a new intake marker delivery system. This research showed that the machine delivered marker was as accurate as the traditional delivery system. Hence, these machines can be used to deliver the intake marker and result in less labor required, no daily restraint of the cattle, and no disruption of daily grazing time or distribution; and therefore, should provide better estimates of grazing intake. This information will be of interest to other researchers investigating the effects of grazing behavior and diets on greenhouse gas emissions.
Technical Abstract: The objective of this experiment was to determine if titanium dioxide (TiO2) dosed through an automated head chamber system (GreenFeed; C-Lock Inc., Rapid City, South Dakota USA) is an acceptable method to measure fecal output. The GreenFeed used on this experiment had a 2 hopper bait dispensing system where hopper 1 contained alfalfa pellets marked with 1% titanium dioxide (TiO2) and hopper 2 contained unmarked alfalfa pellets. Twelve heifers (body weight = 402 ± 5 kg) in a common pasture were stratified by body weight and then randomized to either 1) dosed with TiO2-marked pellets by hand feeding (HFD) or 2) dosed with TiO2-marked pellets by the GreenFeed (GFFD) for 19 days. During the morning (0800), all heifers were offered a pelleted, high-CP supplement at 0.25% of body weight in individual feeding stanchions. The HFD heifers also received 32 g of TiO2-marked pellets at morning feeding, whereas the GFFD heifers received 32 g of unmarked pellets. The GFFD heifers received a single aliquot (32 ± 1.6 g; mean ± standard deviation) of marked pellets at their first visit to the GreenFeed each day with all subsequent 32-g aliquots providing unmarked pellets; HFD heifers received only unmarked pellets. Starting on day 15, fecal samples were collected via rectal grab at feeding and every 12 h for 5 days. A two-one sided t-test method was used to determine agreement and it was determined that the fecal output estimates by HFD and GFFD methods were similar (Probaility = 0.04). There was a difference (Probaility < 0.01; Bartlett’s test for homogenous variances) in variability between the dosing methods for HFD and GFFD (standard deviation = 0.1 and 0.7, respectively). This difference in fecal output variability may have been due to variability of dosing times-of-day for the GFFD heifers (0615 ± 6.2 hours) relative to the constant dosing time-of-day for HFD and constant 0800 and 2000 sampling times-of-day for all animals. This research has highlighted the potential for dosing cattle with an external marker through a GreenFeed configured with two (or more) feed hoppers because estimated fecal output means were similar; however, consideration of the increased variability of the fecal output estimates is needed for future experimental designs.