Can measurements of foraging behaviour predict variation in weight gains of free-ranging cattle?

Authors: Augustine, David; Raynor, Edward; Kearney, Sean; Derner, Justin

Submitted to: Animal Production Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2022
Publication Date: 5/20/2022
Citation: Augustine, D.J., Raynor, E.J., Kearney, S.P., Derner, J.D. 2022. Can measurements of foraging behaviour predict variation in weight gains of free-ranging cattle? Animal Production Science. Special Issue: AAAS|Stobbs Lecture. https://doi.org/10.1071/AN21560.
DOI: https://doi.org/10.1071/AN21560

Interpretive Summary: New types of sensors have been developed that can continuously monitor the location and grazing activity of free-ranging livestock, and transmit that information to the livestock owner remotely. If the measurements collected by these devices can also provide an indication of the animal's nutritional status, such as how rapidly it is gaining weight, this information could help owners make decisions on how and when to move the animals to new pastures, or sell them. We conducted a study that examined whether four metrics of daily foraging behavior collected by sensors placed on yearling steers could serve as indicators of the steers' weight gain. We found the mean daily grazing duration and the steer's velocity while grazing could together predict 62% of the variation in weight gain among the steers involved in the study. These results show that the concept of using sensors to monitor daily foraging behavior as an indicator of animal weight gain has merit, and should be explored further for varying types of cattle and rangeland conditions.

Technical Abstract: Context. Technologies are now available to continuously monitor livestock foraging behaviors, but it remains unclear whether such measurements can meaningfully inform livestock management decisions. Empirical studies in extensive rangelands are needed to quantify relationships between short-term foraging behaviors (e.g. minutes to days) and longer-term measures of animal performance. Aims. We examined whether four daily metrics of foraging behavior (grazing bout duration, grazing time per day, velocity while grazing, and turn angle while grazing) are related to weight gain by free-ranging, yearling steers grazing semi-arid rangeland. Methods. We fitted yearling steers with neck collars supporting a solar-powered device that measured GPS locations at 5-minute intervals and predicted grazing activity at 4-second intervals using an accelerometer. We used these devices to monitor steers in 4 different paddocks that varied in forage quantity, and across two grazing seasons encompassing a wide range of forage conditions. We measured steer weight gain (kg/steer.day) in each paddock during each of three ~60-day time intervals, and we quantified daily foraging behavior during a 15 – 21 day subset of each interval. Results. A model based on only two daily metrics of foraging behavior, mean grazing bout duration (calculated at a 5-minute resolution) and mean velocity while grazing, explained 62% of the variation in animal weight gain. Conclusions. Daily metrics of foraging behavior vary substantially in response to varying foraging conditions in space and time, and can effectively serve as indicators of variation in cattle weight gain. Implications. On-animal sensors that monitor foraging behavior have the potential to transmit indicators to livestock managers in real time (e.g. daily) to help inform decisions such as the when to move animals among paddocks, or when to sell or transition animals from rangeland to confined feeding operations.