Well, it may not be warm but, technically spring, also known as lambing
season, is here. The other day someone asked me why lambs are always born all
within a few weeks of each other. I blinked
a couple times while I processed that fact that things sheep people take for
granted are complete unknowns to non-sheep people. There’s a whole bunch of information
that goes into answering that simple question, ranging from sheep reproduction
to farming economics. I gave her an inadequate two sentence answer, kicking
myself for all the things I left out. So, here’s the long answer; everything
you never wanted to know about sheep sex.
Unlike cows, pigs
and chickens, sheep (for the most part, there are exceptions for you purists
out there) are seasonal breeders. That means there are only certain times of
year that they “come into heat,” are in “estrus,” or cycle. If you’ve never
heard these terms, they are just farming euphemisms for meaning there are only
certain seasons when an animal can be bred and get pregnant. Sheep usually
start cycling around September and stop around December. So, basically they can
only be bred and get pregnant in the fall. (That’s in the northern hemisphere,
folks.)
From an evolutionary
standpoint this makes perfect sense. Gestation, or the length of pregnancy, in
a sheep is about 145 days or 5 months. If sheep were bred in the spring, they’d
lamb in the fall and the lambs would need a lot of nutrition to grow just when
grass and feed was at an all time low (fall into winter). If they were bred in
the summer, they’d lamb in the winter and most likely would freeze to death if
they lived in a cold climate. Even with a barn, keeping a new born lamb alive
in subzero weather is hard. I can testify to this personally, having warmed up
a lot of frozen lambs in warm water in the kitchen sink or kept orphans in the
kitchen by the wood stove.
So, ewes start
coming into heat, or cycling, or being able to be bred in early fall. But they
can’t be bred every day. They cycle like anyone else. And this is where it gets
difficult to explain to non-animal people. Animal people are all about biology
and sex. Regular people, the ones that don’t raise horses, cows, sheep, pigs,
or goats, often don’t know how their own bodies work, no less how a sheep’s
does. But let’s give it go. Every female of any mammalian species releases an
egg or ovum every so many days and can be bred at that time. For sheep, that’s
every 16 days. If you have a flock of sheep that means in the fall all of them in
any 16 day period all your sheep should come into heat once.
So here’s how a
farmer does it. She decides when in the late winter to late spring she wants to
lamb. Some will lamb early to have lambs ready to be sold for slaughter by
Easter. Others want their lambs to go out on grass in May and grow out on
grass, so they’ll aim to lamb in April. So the farmer decides what month she wants
to lamb. Then she figures out when five month ahead is. She puts the ram (or
rams) in with the ewes five months ahead. Usually the ram stays with the ewes
for only a month or 32 days. That’s two heat cycles and we assume everyone that
can be bred will be bred within two heat cycles. That also means everyone will
lamb within a one month period.
Lambing season is
hard. If you’ve got 30 ewes, odds are one will lamb every day. If you’ve got
300 ewes, odds are 10 will lamb a day. Most ewes need no help lambing, but
still you want to be there to make sure the lambs get cleaned off and dried so
they don’t get cold. You want to be sure they find the teats and suckle. You
want to be sure if the ewe has two or three lambs she accepts them all and
doesn’t put all her attention on the last, forgetting about the first. You want
to be sure no one steals her lambs. You want to be sure they get separated from
the others so they have some “mommy and me time” to bond.
(It’s a lot like humans, actually. When I was in nursing
school, the maternal nursing instructor said “what we worry about with newborns
is that they are kept warm, that they eat, and that they bond to their mom.” That’s
no different from sheep or cows, but the instructor and apparently human
mothers don’t like having that pointed out to them. )
Anyway, back to sheep. Lambing in one month means for
that month you have a lot of sleepless nights. For some odd reason sheep like
to lamb at night, usually on the very coldest night if at all possible. Not
being there means some lambs may die. So, most farmers are up every few hours
checking on their sheep during lambing season. But once it’s over, it’s over.
You get a barn or pasture full of bouncing happy lambs and you can sleep till
next year, when you do it all over again.
