Application of Virtual Fencing for the management of Limousin cows at pasture

Abstract

A potential use of pasture-based systems requires an efficient grazing management strategy. Thanks to the Virtual Fencing (VF) physical fences are replaced by virtual ones and, when the animals approach the boundaries, they receive a paired stimulus: an audio cue followed by a low electrical pulse if animals cross over the fences. This study aims to i) to evaluate the animal's ability to learn, and then respond positively, to VF ii) VFs’ efficiency to manage the herd within grazing areas virtually delimitated; iii) to assess the chronic stress related to the VF, evaluating the hair cortisol concentration (HCC), during the experiment. Twenty Limousine cows were fitted with a commercial VF-GPS collars (Nofence AS, Batnfjordsør, Norway). The experiment was divided into four trials: Trial zero (T0) with inactive collars to let the animals get acquainted with them; Trial one (T1) where three of the four virtual boundaries coincided with the physical ones, while the virtual one was set across the pasture to restrict the grazing area; Trial two (T2) in which the grazing area was further extended moving forwards the virtual board; Trial three (T3) in which the virtual line was set longways to the pasture. Results show a significant decrease of stimuli delivered (i.e., sounds and electrical pulses) (p < 0.001), among trials. Moreover, a reduction (p < 0.0250) in the ratio between sounds and electrical pulses was observed between T1 and T3, with T2 being like both. Regarding the cows’ learning capacity, the events in which the sounds were followed by electrical pulses were significantly less in T3 (p < 0.001). Furthermore, in T3 the duration of the audio tones was lower than T1 and T2 (p < 0.0005). Animals were increasingly kept inside the inclusion zones during the trials, with the lowest number of escape events from the inclusion zone registered in T3 (p < 0.001). No differences were observed in the HCC before and after the VF treatment. The progressive reduction of the studied parameters between following sessions, indicates an increase in associative learning through time. VF virtual fencing has proven to be an effective tool in managing Limousin cows at pasture However, future research is needed to evaluate the animals’ performances in terms of grazing activities and on the assessment of chronic stress conditions as well.