Adequate ewe nutrition during
the last six weeks of pregnancy, when 75 per cent of foetal growth
occurs, is essential to ensure appropriate lamb
Pregnancy is divided into three stages
First trimester (days1-45)
Second trimester (days
45-90) - Placental development
Third trimester(days 90-143)
- Foetal growth and development
First trimester (days
Dietary energy supply around
the time of implantation is likely to be adequate because autumn
grass is still available after flushing ewes and there is very
little energy demand from the developing foetus.
Fig 1: Dietary
energy supply during the first trimester is likely to be adequate
because autumn grass is still available.
Second trimester (days
The effect of ewe
undernutrition during second (mid-) trimester on placental
development and subsequent lamb birthweight has been demonstrated
under experimental conditions but weather and/or grazing conditions
need to be severe (winter storms) for at least14 days to seriously
impair placental development. However, severe fluke infestation can
exert this effect on development of the placenta.
Reduced lamb birthweight can
occur when placental development has been limited by competition
within the uterine horn when three embryos implanted and underwent
early foetal development but one foetus failed to develop further
and was resorbed leaving the other developing foetus in the same
horn much smaller than normal and unable to compensate. This
situation often results in the birth of twins with disproportionate
weights e.g. 5.5 kg versus 3.5 kg.
Restricted placental growth in one uterine horn has resulted in the
birth of twins with disproportionate weights e.g. 3.5 kg
(restricted growth - background) versus 5.5 kg (normal growth -
Third trimester (days
Many studies have found
significantly higher mortality in lambs from underfed ewes. The
effects are greater for triplet than twin lambs; singletons were
largely unaffected by dam nutritional status.
Readers are directed to the
NADIS article "Feeding the pregnant ewe in December 2007 and urged
to consult their veterinary surgeon if they are
Body condition scoring is
based on feeling the amount of muscle and fat deposition over and
around the vertebrae in the loin region. These vertebrae have a
vertical bony protrusion (dorsal spinous process) and a short
horizontal protrusion on each side (transverse processes). The ease
with which these protrusions can be felt is used to assess a
sheep's body condition score.
The animal should be standing
in a relaxed position. It should
not be tense, crushed by other
animals or held in a crush.
If the animal is tense it is not
possible to feel the short ribs and
get an accurate condition score
Condition Score 1
Score 1-Backbone (spinous
The bones form an elevated narrow ridge. Each vertebral process
can be felt easily as a bone under the skin. There is only a
very small eye muscle. The sheep is strong but
Score 1-Short Ribs (transverse
The ends of the short ribs are very obvious. It is easy to feel
the square shape of the ends. Using fingers spread 1cm apart, it
feels like the fingernail under the skin with practically no
The spinous processes are elevated but the points are rounded
with muscle. It is easy to press between each bone. There
is a reasonable eye muscle(store condition).
The ends of the short ribs are rounded but it is easy to press
between them. Using fingers spread 0.5cm apart, the ends feel
rounded like finger ends. They are covered with flesh but it is
easy to press under and between them.
The spinous processes are only slightly elevated above a full
eye muscle. It is possible to feel each rounded bone but not
to press between them. (Forward store condition ideal for most lamb
markets now. No excess fat).
The ends of short ribs are well rounded and filled in with muscle.
Using 4 fingers pressed tightly together, it is possible to feel
the rounded ends but not between them. They are well covered and
filled in with muscle.
It is possible to feel most spinal processes with pressure. The
backbone is a smooth slightly raised ridge above full eye
muscles and the skin floats over it.
It is only possible to feel or sense one or two short ribs and
only possible to press under them with difficulty. It feels like
the side of the palm, where maybe one end can just be
The spine may only be felt (if at all) by pressing down
firmly between the fat covered eye muscles. A bustle of fat may
appear over the tail (wasteful and uneconomic).
It is virtually impossible to feel under the ends as the triangle
formed by the long ribs and hip bone is filled with meat and fat.
The short rib ends cannot be felt.
In most typical sheep flocks, over 90 percent of the
sheep should have a body condition score of 2 to
Fig 3: Ewes must be vaccinated against the
clostridial diseases four weeks before lambing.
Ewes must be vaccinated
against the clostridial diseases four weeks before lambing. It is
advisable to vaccinate the flock as two separate groups with the
later lambing ewes vaccinated one week to 10 days later than those
ewes lambing during the first week.
Restrain the sheep
adequately in the corner of the pen or raceway
Part the fleece to the
Tent the skin with the free
hand (not holding the injector)
Slide the needle parallel
with the body surface through the skin near the base of the skin
tent. Observe that the needle has penetrated the skin.
Slight resistance may be
felt as the solution is injected subcutaneously
Fig 4: Vaccinate
ewes when fleeces are dry
The fleeces must be dry when
sheep are vaccinated and care must be taken to ensure correct
subcutaneous injection of every ewe. Subcutaneous injection of ewes
when the fleece is wet can result in abscess formation. Speed is
not important, careful and gentle handling of the pregnant ewes is
essential during the procedure. By ensuring ewes are in good
condition at vaccination time, and receiving an appropriate level
of supplementation as determined by the blood samples collected
(NADIS health bulletin December 2007), you will guarantee plentiful
accumulation of protective antibodies in the colostrum at lambing
If sheep are vaccinated with
a combined pasteurella/clostridial vaccine and erysipelas vaccine,
the interval between the two products should be at least one week.
Further advice should be obtained from your veterinary surgeon if
bluetongue vaccine is used around this time.
The common diseases
of ewes during late gestation includes:
Ovine pregnancy toxaemia (twin lamb
Ovine pregnancy toxaemia is
most commonly encountered in lowground flocks affecting older ewes
carrying three or more lambs during the last month of gestation. On
farms which rely almost exclusively upon pasture-based systems with
little supplementary feeding, ovine pregnancy toxaemia is seen in
severely underfed twin-bearing ewes.
Ovine pregnancy toxaemia
occurs following a period of severe energy shortage, whether the
result of poor roughage quality, inadequate concentrate allowance
or high foetal demand, but clinical signs can be precipitated by a
sudden stressful event such as adverse weather conditions,
handling, vaccination or housing.
Fig 5: Death of
a twin-bearing Blackface ewe caused by feeding only poor quality
silage at irregular intervals - note the lack of available
The early clinical signs of
ovine pregnancy toxaemia include disorientation leading to
isolation from the remainder of the flock. Over the next 24 to 48
hours affected ewes become increasingly dull and depressed and are
easily caught because they are blind.
Head pressing into the corner
of a pen is a common finding. Continuous fine muscle tremors may be
observed around the muzzle and affecting the ears. Ewes often
become recumbent with the hind legs held out behind the ewe.
Inability to stand leads to urine scalding of the ewe's skin and
Clinical signs of
pregnancy toxaemia (listed as the disease
Video Clip - Click on the picture
Fig 6: Over 24
to 48 hours affected ewes become increasingly dull and depressed
and are easily caught because they are
Fig 7: Head
pressing behaviour develops later in the disease
ovine pregnancy toxaemia
The response of ovine
pregnancy toxaemia to treatment is generally poor even when
clinical signs are detected early. Housed ewes should be penned
separately and offered palatable feeds to promote appetite, and
fresh water. If ewes are housed, turnout to good pasture may
promote appetite although such grazing is seldom available.
Treatment with propylene glycol, intravenous glucose injection, and
glucocorticoid injection is successful in approximately 30% of
cases which are still able to walk when treatments
Palatable feeds to promote
appetite, and fresh water
Drench with propylene
Ewes with pregnancy toxaemia
must be checked at least twice daily for signs of abortion/lambing
because they may be too weak to expel the foetuses/lambs. Failure
to expel dead foetuses leads to them becoming rotten, releasing
poisons into the ewe's system which leads to her death. Those ewes
which do recover from pregnancy toxaemia are rarely able to nurse a
single lamb and should generally be culled once they have regained
body condition. Wool slip occurs commonly in these recovered ewes
four to six weeks after abortion/lambing.
Ewes with multiple lambs must
be fed appropriate levels of high quality roughages and
supplementary concentrate feeding during the last six weeks of
pregnancy. (see NADIS health bulletin December 2007).
Fig 8: Woolslip
after pregnancy toxaemia.
Hypocalcaemia is not uncommon
in 3-crop or older ewes maintained at pasture during late
gestation, but can also occur sporadically during early lactation.
Hypocalcaemia is often observed when ewes are brought down off hill
grazing onto improved pastures prior to lambing. "Outbreaks" of
hypocalcaemia can result from errors in formulating home-mix
rations, incorrect mineral supplementation, stress related events
such as dog-worrying, movement on to good pastures prior to
lambing, or following housing.
Affected ewes are depressed,
weak, and unable to stand even when supported. There is rumen
stasis with the development of bloat. Passive reflux of rumen
contents may occur with green fluid present at the nostrils and
around the lower jaw. Without appropriate therapy, the condition
develops to coma, and death follows 24 to 48 hours
Clinical signs of
Depressed, weak unable to
Rumenal stasis and
Reflux of ruminal contents
with green fluid around nostrils and lower jaw
Coma and death within 48-72
There is a rapid response to
slow intravenous administration of 20-40 mls of a 40% calcium
borogluconate solution given over 30 to 60 seconds. Eructation is
observed 1-2 minutes after intravenous calcium administration.
Characteristically, ewes will stand within 5 minutes of intravenous
injection, urinate and wander off to rejoin the rest of the flock.
The response to subcutaneous administration of 60-80 mls of 40%
calcium borogluconate solution injected over the thoracic wall
behind the shoulder may take up to four hours especially if the
solution had not been warmed to body temperature and injected at
Fig 9: There is
a rapid response to slow intravenous administration of 20-40 mls of
a 40% calcium borogluconate solution given over 30 to 60
Fig 10: Affected
ewes are depressed, weak, and unable to
Fig 11: Rapid
response to intravenous calcium borogluconate (see fig
Addition of appropriate
minerals to the ration during pregnancy and thorough mixing are
essential to prevent hypocalcaemia. Outbreaks of hypocalcaemia
occurring over two to three days may still result after stressful
events such as movement or housing.
Insufficient mixing of minerals in this home mix