   Lambs fall victim to severe spring weather  THOUSANDS of new-
born lambs have been killed by severe winds and rain that have
swept through parts of Britain, writes Nicholas Schoon.  Sheep
farmers had been expecting fewer lambs this season because the
proportion of pregnant ewes carrying twins and triplets rather
than singletons was sharply down. This dearth of multiple births
is put down to particularly cold, wet weather at tupping time
last autumn when the rams were brought in to mate.  The ewes may
have been in poor condition at the time of conception last year
or soon afterwards. Now, in the spring, their lambs are being
exposed to equally vicious weather conditions.  Each year 23
million lambs are born in Britain, starting in January in the
southern lowlands and ending as late as May in more northerly
uplands.  Farmers estimate that they lose up to 5 per cent of
lambs at birth or soon afterwards, but this year the National
Farmers' Union in south-west England is making an estimate of 8
per cent.  John T