Assessing the effect of the changes in fattening stages and seasons on the amounts of movement and energy expenditure of fattening cattle in grazing condition using GPS

The beef fattening production system in Japan typically uses a large amount of imported feed under housing management. Since this system has several economic and environmental problems, the grazing fattening system using Japanese Brown cattle (a local breed which is thought to be suitable for grazing system) has recently been receiving attention. However, there have been few studies about the amounts of movement and energy expenditure (EE) of fattening Japanese Brown cattle in the grazing condition, and consequently, beef producers must be subjective to determine the amount of supplemental feeds. Therefore, in the present study, we evaluated the movement and energy expenditure of fattening Japanese Brown cattle under grazing conditions using Global Positioning System (GPS). The experiments were carried out during 2 seasons in 2015: summer and autumn. The experiments were conducted at three pastures of Kumamoto Agricultural Research Center with nine Japanese Brown fattening steers (Three steers for each pasture). Using GPS collars, positional data were collected at 1-min intervals during one week for each steer in a period. Home range, slope gradient, average walking speed, walking distance, vertical locomotion and the ratio of EE in walking to standing (EE ratio) were calculated from GPS points and Digital Elevation Map (DEM) model. The data were separated into two fattening stage (early and late stages of fattening) by the threshold value of 500 kg of body weight. We analyzed the effects of the fattening stage and season on the calculated values, and gained the least square means. The results indicated that EEr and movements varied significantly (P<0.05) between fattening stages and seasons; EEr and movements were higher in the late stage of fattening than the early stage and in summer than autumn.