23 February 1996

Ewes mothering traits vital for lowest lamb mortality

Mis-mothering is one of the main reasons why 15% of lambs die within a few days of birth. Rebecca Austin reports on Scottish research to reduce lamb mortality

LAMB mortality is the focus of a five-year Scottish Agricultural College trial set up two years ago.

It seeks to find out why ewes show good or poor maternal behaviour and how that relates to oestrogen and progesterone levels and to oxytocin release.

Ewe behaviour at lambing is primed by progesterone and oestrogen levels in the bloodstream, particularly in late pregnancy. These two hormones act in the brain to increase the number of receptors for oxytocin, another hormone released at lambing, to bond with. That link-up that triggers maternal behaviour in the ewe.

In the first two years project leader Cathy Dwyer compared behavioural differences in Suffolk and Scottish Blackface ewes. Gimmers were first mated to rams of their own breed. The next year single embryos were implanted in ewes of the different breed (Suffolk embryos in the Blackface or vice versa) to study effects of lamb behaviour and ewe behaviour and physiology.

Dr Dwyer found that it was the Suffolk lamb that influenced ease of lambing and not the breed of ewe. In total 25% of the Suffolk and Scottish Blackface ewes needed help at lambing and 80% of these were carrying Suffolk lambs.

Suffolk lambs took twice as long to get on their feet and even longer to find the udder than Blackface lambs. Most of the latter were on their feet in 15 minutes and 75% found the udder within an hour. In fact up to 90% of Blackie lambs had sucked within two hours, compared with only 65% of Suffolk lambs.

All ewes exhibited a similar behaviour pattern. As expected they got up, licked the lamb and would emit a rumbling bleat and in some cases paw lambs in an attempt to get them up. As gimmers, Blackface ewes bleated twice as often as Suffolks but when experienced bleated half as often as Suffolks. Blackface ewes licked their lambs intensively for at least an hour; Suffolks groomed less, stopping and starting more often.

Work is funded by the Scottish Office of Agriculture, Environ-ment and Fisheries.

Time spent licking lambs is vital.