A SIMPLE METHOD FOR FOSTERING LAMBS USING ANESTROUS EWES WITH ARTIFICIALLY INDUCED LACTATION AND MATERNAL-BEHAVIOR

The possibility of a simple method for using anoestrous ewes to foster orphan or triplet lambs was investigated. Twenty-two anoestrous ewes (12 multiparous and ten nulliparous) were given vaginal sponges containing medroxyprogesterone acetate (250 mg) and oestradiol dipropionate (ODP) (25 mg) for 2 weeks. When these were removed a second sponge was inserted containing the same concentration of progesterone and 50 mg of ODP. This second sponge was left in place for a further 4 weeks and significant udder development (one-quarter to one-third of that seen in animals at parturition) was seen in all of the multiparous ewes and in eight out of ten of the nulliparous ones. Plasma prolactin concentrations in these animals were increased around ten-fold by this treatment and the first milk expressed after the 6 week treatment period had the colouring and consistency of colostrum. Twelve of the ewes (eight multiparous and four nulliparous) were presented with lambs ranging from 30 min to 6 days old. None of the ewes showed full maternal acceptance of lambs following the hormone treatment alone, but after 2-3 min of mechanical stimulation of the vagina and cervix they all immediately became maternal towards the lambs, formed a selective bond with them within 3 h, and reared them successfully through until weaning (one lamb died 1 week after fostering). The initial quality of maternal care was indistinguishable from that of 12 normal post-partum ewes. Only one lamb was raised by each ewe due to the low level of lactation induced, but in all cases udder development was increased as a result of suckling and by 14-16 weeks post-fostering there were no obvious differences between the sizes of lambs reared by normal post-parturient sheep and those reared by the artificial foster mothers.