Evaluating a Walk-over-Weighing system for the automatic monitoring of growth in postweaned Mérinos d’Arles ewe lambs under Mediterranean grazing conditions

Live weight (LW) is a key and conventional indicator for monitoring and assessing overall animal performance and welfare, representing the progress through different physiological stages, while providing close indication of individual physical and health status. Measuring LW in practice is still, however, quite rare and infrequent under commercial sheep farming conditions, mainly because sessions are time-consuming, stressful either for the operator or the animals. A Walk-over-Weighing (WoW) system was tested in this experiment lasting 14 weeks (i.e. 3 weeks for acclimation and adaptation and 11 weeks for data collection). We validated its use for routine and frequent monitoring of growth rate in postweaned Merinos d’Arles ewe lambs (n = 100), reared under Mediterranean grazing conditions. The necessity for an initial adaptation period of the animals was confirmed. Also, the importance of conducting an effective data cleaning procedure of the raw database automatically collected by the WoW was corroborated. Adaptation of naive ewe lambs enabled the required voluntary passages across the weighing platform and a high volume of individual and daily data after 2–3 weeks. Close monitoring of individual growth was then possible after performing sound data cleaning. A good agreement was demonstrated between WoW LW and a reference LW value (measured with a standard static scale). At the individual level, even with the lowest number of LW values collected with WoW, it was possible to monitor variations in LW at daily intervals. The establishment of an early warning system to help farmer decision-making could therefore be possible. Our results show interesting prospects for more accurate and frequent monitoring of LW in grazing sheep without human intervention, compared to what is currently carried out on commercial farms.