To maximise ewe flock performance at lambing you need to minimise both ewe and lamb wastage. In New Zealand it is estimated that between 5-25% of lambs die before they are weaned, with the majority dying around lambing1.
A sheep that has rolled over onto its back is called a “cast” sheep. It may not be able to get up without assistance. This happens most commonly with short, stocky sheep with full fleeces on flat terrain. Heavily pregnant ewes are most prone. Cast sheep can become distressed and die within a short period of time if they are not rolled back into a normal position. When back on their feet, they may need to be supported for a few minutes to ensure they are steady.
Vaginal Prolapse (Bearings)
The exact cause of bearings is not known but appears to be associated with various risk factors.
Ewes carrying twins are 5.3 times more likely to have a bearing than single ewes and triplet ewes 11.3 times more likely.
Topography also plays a role in that ewes lambing on moderate to steep paddocks are more at risk than those on flat paddocks.
Shearing in the 3 months prior to mating and in the second half of pregnancy appears to offer some protection from bearings.
Ewes which gain weight from mating to scanning are at higher risk.
Other identified risk factors are feeding salt or swedes in late pregnancy.1
A mass of pink tissue hanging from the vulva, usually in heavily pregnant ewes carrying twins or triplets.
Dry ewes can also have bearings (the cause is likely to be different from those seen in pregnant ewes).
The “bearing” may be the inverted (inside out) vagina.
If it’s big it may contain the bladder, the cervix and the uterus (womb).
Treatment and Prevention
If the bearing is recent and small, you may be able to push it back in.
Firstly disinfect the prolapse then attempt pushing it back in, emptying the bladder and pointing the ewe downhill will assist in this.
In some cases, if the bearing has dried out or if it is a very large bearing, euthanasia may be the best option.
A veterinarian can be called to complete a caesarian in order to save the lambs. If the bearing does retract, it is important to retain the bearing to prevent it coming out again. This is done by the vet placing sutures around the vagina and vulva or with the placement of a bearing retainer.
At risk ewes should be kept off hilly pastures and encouraged to do gentle exercise.
It is also important to maintain a steady diet, reduce the amount of fibre in their diet, and avoid ewes from exceeding a BCS of 4.
Dystocia (Difficulty In Lambing)
Dystocia is an important cause of death in single lambs, but can also affect twin lambs.
Treatment and Prevention
A difficult birth can be caused by the lamb being too large for the ewe’s birth canal.
Ram selection can be a contributing factor, particularly where terminal sire rams are used over small hoggets or ewes.
Ensure ewes are well grown as hoggets and in adequate but not fat body condition.
Malpresentation e.g. head or leg back, or tail presented to birth canal, or ewe weakness, or over nutrition of ewes in late pregnancy.
Force should not be used to deliver lambs (alive or dead) due to the danger of injury to the ewe and lamb.
Use lubrication, manipulation and adjust the presentation so that the lamb’s head and feet (if head first), or two hind feet (if tail first), are together as they exit the birth canal.
Tell-tale signs of birth trauma include large-headed lambs, no evidence of walking or breathing, subcutaneous oedema, empty stomach and haemorrhage of the liver, or of the brain or spinal cord.
Apart from lamb deaths, dystocia also accounts for a large proportion of ewe deaths. Ewes that are given assistance at birth should be clearly marked, and the lamb also identified for later culling. This is because ewes will often go on to have birth difficulties in subsequent years, and lambs from these ewes may also not be good breeders.
Wet-drying ewes is also a good chance to examine them for mastitis. The udder will be swollen and painful, hot and discoloured, and ewes may be lame. This can be a major cause of lamb loss, especially if it extends into both halves of the udder.
Conversely, mastitis may be caused by ewes losing lambs.
Other causes are milk stasis at weaning, damage from lambs or other sheep, infections including scabby mouth, dirty conditions such as sheep camps, or injury from shearing.
Lambs born to ewes with mastitis at docking have been shown to be 3x less likely to survive to weaning.
Lambs born to ewes with mastitis at weaning have been shown to be 3.9x less likely to survive to weaning.2
Starvation / Exposure
Starvation/exposure is arguably the most common cause of lamb loss. It is estimated that between 25-50% of the losses that occur during the first week of life are due to this3.
There are multiple predisposing factors that will lead to lambs dying due to this syndrome.
Goiter or subclinical iodine deficiency.
Infectious agents such as Campylobacter or Toxoplasmosis.
Unfavorable weather conditions (e.g. cold wind and rain).
Steep and poorly sheltered lambing paddocks.
Mastitis or hard udders.
Lack of milk production by the ewe.
Disturbance of the ewe during or just after birth.
Techniques to Reduce Losses3
Ensure ewes are fed adequately during pregnancy.
Scan ewes and split singles and multiple ewes for differential feeding.
Avoid using terminal sire rams over hoggets or small ewes.
Provide trace element supplementation where it is required (Iodine and Selenium).
Provide shelter in lambing paddocks.
Cull ewes with udder defects.
Minimise disturbance during lambing beats.
Most commonly seen in lambs born on wet, muddy and contaminated environments.
Often where lambs may have not received enough colostrum.
Infection (e.g. Fusibacterium necrophorum and Arcanobacter pyogenes) enters through the naval and affects various organs of the body.
(rarely seen in New Zealand, more common in housed environments)
Affects lambs 1-3 days of age. Infection of the intestinal tract due to non enteric forms of E. coli. Often leads to distention of the abdomen, pain and a profuse watery discharge from the mouth. Lambs die very quickly.
Campylobacter Toxoplasmosis Hairy shaker
These causes of abortion can lead to the birth of weak lambs that die soon after birth.
Both subclinical iodine deficiency and clinical disease (Goiter) can lead to the birth of weak lambs that die soon after birth. Diagnosis of subclinical iodine deficiency is done by dissecting out the thyroid gland of about 20 new born dead lambs and weighing both the glands and the lamb to work out the thyroid to lamb ratio. A ratio of greater than 0.4g/kg is indicative of subclinical iodine deficiency and ratio’s over 0.7g/kg indicative of goiter.
Low selenium levels can lead to lambs being born dead (congenital) or dying 3-6 weeks after birth (acquired) with white muscle disease.
Click here for more information on Trace Element Deficiency.
Low bodyweight lambs struggle to maintain body temperature. All lambs have a high surface area to bodyweight ratio, but particularly those under 3-4kg rapidly lose energy if left exposed.
Lambs that suckle strongly can survive well in cold conditions, but in general lambs are not tolerant of wind.
Pasture height greater than 10cm improves lamb survival as it allows lambs to take shelter from wind, particularly in cold, wet conditions. Shelter belts and windbreaks can be maintained in lambing paddocks to improve ewe and lamb comfort.
Stocking Density and Husbandry at Lambing
Twin-bearing ewes have higher rates of lamb survival if lambing in smaller mobs (100 to maximum 200). This is especially important for maidens, as they are inexperienced and more likely to ignore the lamb’s attempts to suckle.
Pasture availability should be highest for twin-bearing ewes (>1200kg DM/ha) to avoid ewes needing to walk away from lambs looking for feed.
Mothering ability is repeatable across years, so where possible take note of ewes that fail to rear a lamb in a year.
Good maternal characteristics are enhanced within a flock by:
Choosing ewes that are early to conceive and bear twins (determined by ultrasound scanning and/or observation at lambing).
Wet/drying ewes at docking/tailing to remove ewes that failed to rear a lamb and tag the ewes that did not conceive, or had pregnancy loss.
Avoid interruptions to lambing such as chasing with dogs, driving into a paddock if ewes aren’t accustomed, loud noises.
Select and manage ewes for low rates of dystocia.
Good predator control (e.g. wild pigs and dogs).
Wet / Drying Ewes
Wet/drying ewes can be done by looking at and feeling each ewe’s udder at lamb marking. Ewes fall into one of three categories depending on udder characteristics.
Udder is swollen, with milk easily squeezed from the teat, often with saliva on the teat.
Ewe is rearing a lamb.
Keep ewe for continued production.
Udder is swollen but has no or little milk and no saliva on the teat.
The ewe has lambed but lost the lamb.
Tag the ewe for culling.
Udder is small, flaccid, empty.
The ewe has not lambed, either due to failure to conceive or pregnancy loss.
Tag or immediately draft the ewe for culling.
Check udders for lump, signs of swelling, heat and redness. Look for clots or blood.
Treat active infection with antibiotics. Mark ewe.
Recheck at weaning. Cull if lumps or infection still present.
Docking / Tailing
Lambs should be docked/tailed between the ages of 2 and 12 weeks of age, with the youngest animal in the mob being at least 24 hours old. This is to ensure the maternal bond can form. If lambing extends for more than 6 weeks it is best to have 2 separate sessions.
Lambs should be vaccinated with a clostridial vaccine. This can be given at the same time as docking/tailing. In lambs, for a flying start with optimal protection, begin the vaccination programme at docking, and give the booster 4-6 weeks later or at weaning.
R Jackson, RPN Hilson, AR Roe, N Perkins, C Heuer and DM West. Epidemiology of vaginal prolapse in mixed-age ewes in New Zealand. New Zealand Veterinary Journal, 62(6), 328–337, 2014)
KJ Griffiths, AL Ridler, CWR Compton, RA Corner-Thomas & PR Kenyon. Associations between lamb growth to weaning and dam udder and teat scores. N Z Vet Journal 2019 1-8.
West DM. Bruere AN. Ridler AL. The sheep. Health, disease and production. 2nd edition p84-86.