94 Characterizing Yearling Beef Steers Grazing on Smooth Bromegrass Pasture Using Global Positioning Technology

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Abstract Extensive grazing systems often vary in pasture size and terrain, making it challenging for ranchers to accurately locate livestock through visual appraisal. Using satellite-based global positioning systems (GPS), accurate position data can be provided to track animal movements that could inform grazing management decisions. This study aimed to: 1) assess two modern GPS devices for functionality by calculating fix success rate, and 2) evaluate the relationship between average daily distance traveled and average daily weight gain (ADG) performance on yearling steers grazing smooth bromegrass pasture using the GPS devices. Yearling steers (n = 25) grazed a 10.8-ha smooth bromegrass pasture for 156 days from May to September 2021. The temperature ranged from 4.1 to 38.8ºC with an average 22.7ºC and received 490 mm of rainfall. Cattle ADG was 0.65 ± 0.13 kg/d. Each steer was assigned two GPS collars for 28 days to compare two types of sensors. The sensors evaluated were i-gotU GT-600 travel loggers (GU) and Yabby LoRaWAN GPS sensors (YB) utilizing the IoT (Internet of Things) technology. The YB sensor possessed real-time monitoring and remote data access, while data from the GU sensor needed to be removed from the animals and manually downloaded. The YB sensors had a manufacturer declared finest positioning accuracy of 4.6 m, while that of the GU sensor being 9.1 m. With a 10-min sampling rate, battery life of the YB sensors lasted 4 weeks, while the GU sensors demonstrated unreliable battery performance that ranged between 1 to 4 weeks. Fixed success rate (FSR) was calculated for each sensor. Using PROC MIXED of SAS (v 9.4), on average the GU sensors had a 67.1% FSR and the YB sensors observed an 89.9% FSR (P < 0.0001). The YB sensor outweighed the GU sensor on battery life and FSR, thus was utilized throughout the duration of the grazing season. Individual animal traveled distance was calculated after converting the GPS coordinates in decimal degrees to Universal Transverse Mercator coordinates (WGS 1984 UTM zone 14N) in meters. The Euclidean distance between consecutive coordinates was calculated and summed daily to represent the daily traveled distance of an animal. Using all coordinates recorded from YB, steers traveled 2,718 ± 809 m/d. Statistical analysis was conducted using PROC CORR of SAS to determine the correlation between the daily averages of distance traveled and ADG. All values were considered significant α ≤ 0.05. There was no correlation observed between distance traveled and ADG (P ≥ 0.76). Results demonstrate that modern GPS sensors utilizing IoT technology have benefits over traditional GPS sensors and can be used as a tool for extensive grazing livestock tracking.

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