Noseband sensor validation and behavioural indicators for assessing beef cattle grazing on extensive pastures

Abstract Advances in on-animal sensor technologies to monitor location and activity have enhanced the ability to study foraging decisions of free-ranging herbivores. Sensors monitoring jaw movements that quantify ingestive behaviours, such as the RumiWatch (RW) noseband sensor system, have primarily been used in indoor animal housing systems or structurally homogeneous, small pasture (paddock) environments. Continuously monitoring these ingestive behaviours in extensive and heterogeneous rangelands has not been previously conducted. We evaluated the accuracy of the RW noseband sensor system for two grazing seasons in 130-ha pastures (paddocks) composed of native, mixed-species plant communities in a semiarid environment. The noseband sensor was used to compare ingestive behavior at different sites and seasons characterized by varying sward complexity, stocking rate, and levels of forage limitation. We evaluated the noseband sensor against direct visual observations of yearling steers grazing with two different validation studies. First, the time duration of grazing recorded by the sensor was compared to direct visual observation data (Validation Study 1). A high correlation (rs = 0.95) for hourly grazing time resulted between the RW system and visual observations. Second, we examined the ability of the RW system to measure prehension bite rates in distinct plant communities varying in height and leaf angle (Validation Study 2). The accordance between direct observation and measurement by the RW system for bite rate improved from 2019 (Concordance Correlation Coefficient (CCC) = 0.71) to 2020 (CCC = 0.80) after modifications to improve the fit of the halter supporting the noseband sensor. Correlations between the sensor and visual observations increased by ∼17 % with this modification for grazing bouts in mixed-species and midgrass-dominated swards; correlations remained ∼10 % lower in shortgrass-dominated swards. Our results show that the RW system is an effective tool for monitoring free-ranging cattle grazing activity and quantifying bite rates in a heterogeneous rangeland ecosystem. Bite rate measurements are more accurate in swards with vertically oriented stems and leaves compared to lawn-like prostrate swards. Grazing bout length and rumination chew rate may represent behavioral indicators employed in managing animal performance in semiarid rangelands. Our validation study and experimental investigation indicate that the RW noseband sensor is a useful animal-borne sensor technology for research demanding sustained ingestion measurements across mixed-species forage communities.