44 GNSS tracking to phenotype cattle locomotion energy requirements in mountainous rangelands.

Abstract Spatial use patterns of grazing livestock have been widely studied over the last three decades. Selective behavior and adaptation to pasture conditions are two of the mechanisms that result in the spatial distribution of grazers in a paddock. Animal trajectories depend on the availability of resources and the trade-offs associated with moving between areas. A critical component of these tradeoffs is the energy required for locomotion, which can be particularly important when the terrain is rough, as is the case in mountain rangelands. Thus, differences between individuals in energy expenditure for locomotion can serve as phenotypes of adaptation to mountain range grazing. Precision rangeland management (PRM) tools, such as GNSS/GPS tracking collars/tags, can be used to quantify the spatial behavior of grazing cattle. In the present study, 10 cows from a herd of 110 animals were fitted with GNSS collars (Digitanimal Ltd.) in a 1400 ha grazing area in Sierra Nevada National Park (southern Spain). Most of the range had slopes between 30 and 60% (885 ha). In addition, 344 ha had slopes between 15 and 30%, 140 ha had slopes greater than 60%, and only 21 ha had slopes less than 15%. Elevation ranged from 1700 to 2800 m.a.s.l. Various crosses between indigenous and European breeds were present among the monitored animals. Daily 3D trajectories were calculated from GNSS coordinates and digital elevation models using the trajr package for the open-source software R. The locomotion energy requirements associated with each trajectory were estimated based on Brosh et al. (2006), who defined an average requirement per meter of vertical (differentiating between uphill and downhill) and horizontal path (kcal per kg body weight). The body weight of individuals was estimated as the average weight of the breed according to official breeding plans. For crosses, the average body weight of the breeds involved in the cross was used. An analysis of variance (ANOVA) was performed to compare individuals, followed by a post hoc Tukey test to detect statistical groups. The results showed a large phenotypic variability, with some animals expending more than twice as much energy for locomotion as others (P < 0.000). Lighter cows, mostly indigenous breeds and F1 crosses, showed higher locomotion energy expenditure, which means that they spend more proportional energy on locomotion than heavier cows (Table 1). This study presents a novel approach to phenotype grazing behavior using PRM technologies and provides a potential way to select animals better adapted to mountainous rangelands. Selectivity and social behavior may also influence cow movement patterns and merit further investigation.