Reducing mother-young separation distress by inducing ewes into oestrus at the day of weaning

Abstract

AbstractThe aim of this study was to determine whether or not oestrus induction on the day of weaning would reduce the distress experienced by ewes upon separation from lambs. For this, 43 ewes, their eight week-old lambs and six mature rams were used. Prior to weaning, 21 of these ewes were induced to display oestrus on the day of mother-young separation (treated group [T]) while the remaining 22 untreated ewes served as controls (C). T and C ewes were housed together. Blood samples were collected on the day of weaning (prior to mother-young separation and 24 hours later) and then nine days later, for plasma progesterone (P4) and cortisol determination. Lambs were separated from their dams by a wire fence at weaning in full view of each other. Three rams were tethered to posts with 3 m plastic chains in the ewes' pen. T and C groups were simultaneously tested in identical test pens. C ewes showed a greater increase in serum cortisol concentration after separation from lambs (47.64 ± 4.26 n mol l–1) than T ewes (28.79 ± 6.29 n mol l–1). T ewes exhibited fewer vocalisations ewe–1h–1 and fewer vocalisations at 6, 12 and 18 h post separation than C ewes. On the day of weaning, more T ewes were seen to be situated away from lambs and in close proximity to the males, compared to the C group. Thus, more T than C ewes were mounted (14 as opposed to 3) and these received a greater number of mounts (1.02 ± 0.23 per hour, as opposed to 0.11 ± 0.06). It was concluded that by inducing ewes into oestrus at weaning it is possible to reduce the signs of separation distress.