Linking foraging behaviour of free-ranging, lactating beef cows with diet quality and weight gain in semi-arid rangeland

Authors: Augustine, David; REED, MONTE - Producer; Kearney, Sean; Porensky, Lauren; SCASTA, DEREK - University Of Wyoming; PELLATZ, DAVE - Thunder Basin Grasslands Prairie Ecological Association; Derner, Justin

Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2025
Publication Date: 8/28/2025
Citation: Augustine, D.J., Reed, M., Kearney, S.P., Porensky, L.M., Scasta, D.J., Pellatz, D., Derner, J.D. 2025. Linking foraging behaviour of free-ranging, lactating beef cows with diet quality and weight gain in semi-arid rangeland. Applied Animal Behaviour Science. 292. Article e106802. https://doi.org/10.1016/j.applanim.2025.106802.
DOI: https://doi.org/10.1016/j.applanim.2025.106802

Interpretive Summary: Ranchers raising cattle in expansive and rugged rangelands often have difficulty finding and assessing the nutritional condition of their animals. We evaluated the use of a cattle collar that carried (1) a GPS unit for animal tracking, (2) an accelerometer to measure neck and head movement patterns, (3) solar panels on the back of the animal's neck to provide power, and (4) a communication device to send data from the collar to the rancher via satellite transmissions and associated software. Specifically, we examine the use of these devices on lactating cows with calves on a working ranch in eastern Wyoming. We found that the GPS and accelerometer data could be used to measure the cow's foraging behaviors in ways that were correlated with the quality of their diet, and the rate of cow+calf weight gain. These results indicate substantial potential utility for near-real-time monitoring of foraging behavior as an indicator of animal performance via on-animal sensors in extensive rangelands. However, operationalizing such a system will likely depend on continuing improvements in sensor durability and data management efficiency, and reductions in sensor and data transmission costs.

Technical Abstract: Monitoring free-ranging livestock foraging behavior and health with on-animal sensors has emerged as an effective means to enhance adaptive management for ranching operations. We evaluated the use of GPS collars collecting animal locations at 5-min intervals and estimating activity (grazing, walking, or stationary) via a 3-axis accelerometer to quantify foraging behavior of lactating Bos taurus beef cows with calves on a ~7,600 ha working ranch in a sagebrush grassland ecotone in northeast Wyoming. We used the sensor data to quantify five metrics of foraging behavior at a daily time step including (1) mean velocity while grazing (VG), (2) mean grazing bout duration (GBD), (3) mean turn angle while grazing (TAG), (4) total daily grazing time (TTG) and (5) total daily travel distance (TD), and related these metrics to measurements of cattle diet quality, weight gain, and stock density. While foraging behavior metrics varied among individuals, we found that daily estimates of VG, GBD, TAG and TD were all significantly related to stock density and variation in remotely-sensed estimates of dietary crude protein content. Over longer time periods of weeks to months, cattle diet quality and weight gain were significantly related to VG (positive correlation; R2 = 0.49 – 0.79), and GBD (negative correlation; R2 = 0.52 – 0.79). These findings indicate that ranchers have the ability to influence diet quality and animal performance via both the rotation of herds among pastures of varying composition and quality, as well as through changes in herd size relative to pasture size (i.e., animal density). Furthermore, our results indicate there is substantial potential utility for near-real-time monitoring of foraging behavior as an indicator of animal performance via the combination of GPS tracking, accelerometer data, and a method to wirelessly transmit data to the internet. However, operationalizing such a system will likely depend on continuing improvements in sensor durability and data management efficiency, and reductions in sensor and data transmission costs.