Polypay breeding group
Licking her lambs
10 year old ewe with quads
Yearling Katahdin mom
Mary had a little lamb
- Spring lambs
Mother Nature meant for sheep to mate in the fall, so that
their lambs would be born in the spring when the weather is mild
and the grass is plentiful. This scenario would provide the best
chance for lambs to survive and thrive.
Ewes are considered "seasonally, polyestrus" because their reproductive
cycle is controlled by the photoperiod and they come into heat
(estrus) every ~17 days (until they become pregnant) during their fertile period. Photoperiod
is the relationship between light and dark in a 24-hour period.
Ewes are short-day breeders. When day length becomes shorter (in
the fall), this triggers the ewe's brain to release hormones that
jump start the reproductive system. The further away from the
equator the sheep breed originated, the more likely it is to exhibit
these seasonal breeding patterns. Conversely, sheep breeds developed
in the tropics or nearer to the equator are less likely to display
seasonal breeding patterns. Breeds in the U.S. that have less
seasonal breeding patterns include the Dorset, Rambouillet, Polypay,
Karakul, Merino, Finn, and hair sheep.
During their fertile period, ewes will come into estrus (heat)
every approximately 17 days until they are bred or their fertile
period is over. Only during estrus will a ewe allow a ram to mate
her. The duration of estrus is 24 to 36 hours. A ewe in heat will
seek out the male. She may sniff, lick, or nuzzle him. She may
fan her tail. The classic behavior response of the ram when he
detects a ewe in heat is to lift his nose in the air and curl
his upper lip. This is called the Flehmen response.
Though it depends upon breed, nutrition, and management, ewes
can become mothers by the time they reach their first birthday.
This is okay if the ewe lamb has achieved approximately two-thirds
of her mature size (weight) before being bred. Thus, for some
producers, it is commonplace to breed well-grown ewe lambs when
they are 7 to 9 months of age. Other producers wait until their
ewes are 18 months old before breeding them to lamb as 2 year
olds. Different breeds of sheep reach puberty (sexually maturity)
at different ages.
A healthy, mature ram can probably mate 100 (or more) ewes during
a breeding season, though a ratio of 1 mature ram to 30 to 50
ewes is more common to make sure lambing is not too spread out.
Six to 7 month old ram lambs that have achieved approximately
50 percent of their mature size can be used for breeding. Ram
lambs are usually put in with fewer ewes, 15 to 25. Some rams
show a preference for ewes of their own breed or kind.
- Artificial insemination
Artificial insemination (AI) is much more difficult in sheep than other
livestock for several reasons. The ewe has a more complicated
cervix and it is difficult to pass a standard insemination rod
through the many cervical rings. Ewes show fewer visible signs
of estrus, making heat detection more difficult. A teaser ram
is often used to detect heat. However, high levels of conception
are possible when ewes are inseminated with fresh semen deep into
the vagina. Good results are achieved when frozen semen is injected
into the uterine horns via a surgical procedure called laparascopy.
Trans-cervical AI requires special equipment.
A ewe is pregnant for 142 to 152 days, approximately five months
or slighter shorter. Pregnancy is also called gestation. Since
ewes gestate for only five months, it is possible for them to
lamb more often than once per year. While annual lambing is most
common, lambing intervals of 8 months are realistic, especially
in the tropics and with breeds that are less seasonal in their
During her last month of pregnancy, a ewe needs extra nutrition
because her lambs are growing rapidly inside of her and her mammary
tissue is developing. 70 percent of fetal growth occurs during
the last month of pregnancy. The growth of the fetuses is also
reducing her rumen capacity.
If a ewe doesn't get enough feed during late pregnancy, she may
get sick because her unborn lambs are taking all of her nutrient
intake. Thin and fat ewes and ewes carrying multiple fetuses are
most prone to pregnancy toxemia (ketosis). Thus, it is common
to feed grain during late gestation. On the other hand, if a ewe
eats too much during late pregnancy, she may have trouble delivering
her lambs because they may get too big. Fat ewes are also more
prone to problems at lambing time.
On many farms, it is common to vaccinate ewes during late pregnancy
for the colostridial diseases that most commonly affect sheep
and lambs: clostridium perfringins type C & D (overeating
disease) and tetanus. By vaccinating the pregnant ewe, the lambs
will acquire immunity when they drink the colostrum, the first
milk produced by the ewe after lambing. In fact, a pre-lambing vaccination is the only way to protect lambs against type C.
A ewe's immunity to internal parasites (worms) is comprised around
the time of lambing. Scientisits call this phenomenon the "periparturient
rise" in worm eggs. Some producers will deworm their ewes
during the last month of pregnancy to prevent this from happening.
Due to the widespread emergence of drug-resistant worms, a better
strategy might be to increase the protein content of the ration,
as the primary parasite that affects sheep is a a blood sucking
worm (barber pole) that causes blood and protein loss. Higher
protein rations have been shown to reduce egg counts in periparturient
Ewes usually give birth to 1 to 3 lambs at each birthing episode.
Birthing is also called parturition. Twin births (two babies)
are most common in well-fed flocks and with most breeds of sheep.
First-time moms, especially yearlings, are more likely to have
single births, though twins are not uncommon in some breeds. Ewes
produce their largest litters of lambs when they are between the
ages of 3 and 6.
There are some breeds of sheep that average more than two lambs
per litter. In the U.S., the most prolific sheep breeds are Finnsheep
and Romanov. The hair sheep breeds are also very prolific (Katahdin,
St. Croix, and Barbado). The more lambs a ewe ha,s the more feed
she need to produce milk for them. Oftentimes, extra lambs
need to be fostered onto other ewes or artificially reared. Proflic
breeds are not recommended for novice shepherds or in situations
where nutrition is a limiting factor.
Because some sheep are raised in difficult environments, sometimes
it's more desirable for a ewe to have just one lamb. This is because
there may not be enough food for the ewe to support the growth
of two lambs. If the flock has to travel far for food and water,
it's usually better to have one strong lamb than two or three
smaller lambs that may struggle to keep up. Smaller, weaker lambs
that lag behind the flock are more likely to be killed by predators.
- Birth weights
The weight of newborn lambs varies by breed, sex of lamb, litter
number, and ewe nutrition. The lambs from medium to small breeds
are similar in size to human babies, usually between 5 and 10
pounds, with an average of 7 to 8 pounds. When birth weights get
too heavy (relative to the size of the breed), difficult births
can be encountered. Medium-size babies tend to have the highest
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