Induction of maternal behaviour in non-pregnant, hormone-primed ewes

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Abstract
It has been suggested that the induction of maternal behaviour in non-pregnant ewes by treatment with oestrogen and progesterone followed by artificial, mechanical vaginocervical stimulation (VCS), could be used to produce foster mothers for orphan or triplet lambs. To investigate the reliability of the technique, 46 non-pregnant sheep of two breeds (Suffolk (S) and Scottish Blackface (BF)) and two levels of experience (nulliparous (N) and multiparous (M)) were used. All ewes were given 6 weeks of treatment with vaginal sponges containing oestradiol and progesterone, followed by 2 min of VCS and exposure to a neonatal (< 2 days old) foster lamb. Plasma oestrogen and prolactin concentrations were significantly elevated by the hormonal treatment; prolactin was significantly higher in M ewes compared with N ewes (BFN = 91, SN = 107, BFM = 301, SM = 687 μg/l,P< 0·005). Significant udder development was seen in most ewes (proportionately 1·0 Mv.0·62 N, P = 0·01) and more M ewes produced milk than N ewes (0·67v.0·19,P< 0·005). No ewes showed maternal behaviour to the lamb from hormone treatment alone. After VCS, one of 26 N ewes and five of 12 M ewes expressed maternal behaviour. In the M ewes, significantly more S ewes were maternal than BF ewes (proportionately 0·75 SMv.0·25 BFM,P< 0·05). It is concluded that the technique alone is not sufficiently reliable to be a useful fostering aid. It is suggested, however, that previous exposure to neonatal lambs, handling of ewes before testing and using newborn lambs, may be fruitful areas of investigation to improve the technique.

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