Monitoring post-weaning behaviour in Merinos d’Arles ewelambs at grazing with a walk-over-weighing

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إنجليزي. One-hundred weaned Merinos d’Arles female lambs (24.8±3.44 kg of liveweight, LW), were allocated in a grazing experiment under Mediterranean conditions. The objective was to study: (1) their adaptive behaviour during thetransition period (i.e. after being separated from their mothers) and; (2) the adaptation of such naïve ewelambs to voluntarily cross through a walk-over-weighing (WoW), strategically placed in the paddock for the automaticmonitoring of the individual LW. The experiment lasted five weeks. Animals grazed a mixed sward (ryegrass and native herbaceous legumes), and were submitted to a rotational system in paddocks (0.33 ha) grazed during 5 dayseach. The progressive voluntary daily number of passages through the WoW (N°Pass), looking to visit the water trough, molasse and the mineral salt blocs, was assessed, as it was the daily kinetic of visits (CrossK) and the numberof biologically plausible LW records (PlausLW) registered by the WoW. With valid LW records the average daily gain (ADG, g/d) was calculated. The N°Pass increased with time, attaining the last three weeks around 340 passages/d.CrossK shows a normal distribution from 8 am to 6 pm, with a peak of passages between 7 and 8 am. During the first week of the experiment, PlausLW (records/d) was low (28), but improved with time (130, 174, 170 records/d last 3weeks, respectively). Variability in the intra-group ADGs increased between the first and the last week (i.e. sd=0.06 kg/d, sd=0.13 kg/d). According to the overall behaviour and growth performance, it was concluded that these ewelambswere considered adapted to the grazing system as well as to the use of the WoW after 21 d. Using the WoW, under the conditions of this study miming real-life production conditions, allowed us to perform a close monitoring of thegrazing behaviour and performance of these growing animals.