Growth and behaviour of post-weaned Mérinos d'Arlesewe lambs, as measured by a Walk-over-Weighing system under Mediterranean grazing conditions

Liveweight (LW) is a key and conventional indicator for monitoring and assessing overall animal performance and welfare, representing the progress along 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 and the animals. A Walk-over-Weighing (WoW) system, already evaluated with other breeds under different conditions, was tested in this experiment lasting 14 weeks (i.e. 3 for acclimation and adaptation and 11 for data collection). We validated its use for routine and frequent monitoring the growth rate in post-weaned Merinos d'Arles ewe lambs, reared under Mediterranean grazing conditions. Similarly to previous work, the necessity for an initial adaptation period of the animals as well as for an essential data cleaning procedure of the raw database automatically collected by the WoW, were corroborated. Adaptation of naive ewe lambs enabled the required voluntary passages across the weigh 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 cleanings. A strong concordance of WoW LW data with the gold standard (a standard static scale) LW reference data was demonstrated. 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 perspectives for more precise and frequent monitoring of LW in grazing sheep without human intervention, compared to what is currently carried out on commercial farms.