Ewe health challenges at lambing

As ewes approach late pregnancy and lambing, nutrient demands on their body increase in tune with the rapidly growing foetuses inside.

Sheep health experts Dr Paul Nilon, Tasmania and Dr Bruce Watt, Central Tablelands, presented a Making More From Sheep Webinar in May, about the main health challenges ewes experience during this time of late pregnancy.

While Lifetime Ewe Management recommends Merino ewes should be condition score (CS) 3 and above, we tend to run our prime-lambs at ‘too-higher’ condition score – they should be about CS 2.75–3.25. Above this level you begin to get a range of issues including casting, pregnancy toxaemia, prolapse, dystocia (particularly in singles) and foot abscess issues. If ewes are consistently heavier than CS3.5, the you are probably understocked and that will be a key profit driver.

Metabolic diseases hypocalcaemia and pregnancy toxaemia are the most common causes of downer ewes. The conditions often overlap, and hypocalcaemia inevitably leads to pregnancy toxaemia if left untreated. Pregnancy toxaemia is very difficult to treat, so all effort needs to go into prevention. Hypocalcaemia is treatable, but is also best prevented in the first instance.

Pregnancy toxaemia is a complex metabolic disease but the end result is inadequate blood glucose to maintain the ewe’s central nervous system functions.

Determinants include:

  • Older fat ewes, multiple bearing
  • Inadequate feed intake to keep blood glucose high:
    • Poor quality feed or an inadequate amount
    • Lameness preventing feeding, eg. foot abscess
    • Prolonged yarding, handling or transport
  • Can also have ‘not so fat’ ewe pregnancy toxaemia, which has slightly different physiology and better treatment outcomes.

Clinical signs:

  • Sheep are unresponsive, ‘blind’ or staring into space. Once down they are profoundly depressed, and will hold their head towards their flank.
  • You may smell ketones on her breath, and many animals will have a wool-break.
  • Generally, there are not huge numbers affected at once, but it will be progressive through the mob.

Treatment:

  • Early stages (before they go down): oral propylene glycol, oral or IV glucose or dextrose, there is evidence that Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) may help these animals (eg. Metacam used for lamb marking); induce lambing (drugs from local vet).

Downers: not many will respond, so Paul suggested to play them Mozart’s requiem!

  • Can have moderate success treating skinny ewe pregnancy toxaemia with glycol/dextrose.

Prevention:

  • Run sheep at a slightly lighter weight (CS 2.75-3.25)
  • Grain supplementation: if they have good feed in front of them, they may only need a lolly/trickle (eg. 100-150g/hd/day). You may need to feed enough energy to maintain body condition if there’s a gross deficiency.
  • Deft, quick handling at pre-lambing treatments. Get them in and out of the shed quickly and back on feed.
  • Treat foot disease, particularly foot abscess, with antibiotics and NSAID’s (Metacam injection or Buccalgesic orally) to relieve pain.
  • If in containment, it’s better to feed pregnant ewes daily than just three times/week in the last 5-6 weeks of feeding, before turning the ewes into the paddock for lambing.

Hypocalcaemia occurs in the last month of pregnancy as a result of sudden changes of food, or stressors such as prolonged cold weather off-shears. The critical event is insufficient circulating calcium to maintain neuromuscular function.

Determinants include:

  • Change from dry to lush pasture in late pregnancy
  • Prolonged yarding, handling or transport
  • Chronic grain feeding without calcium supplement. Chronic exposure to irrigated green grass or winter cereals. Native pastures are rarely deficient in calcium.

Clinical signs:

  • Sheep go down suddenly, and appear relatively bright and alert in the early stages. They will become dull over time. A proportion will have a characteristic frog-back leg position
  • Can affect 10’s to 100’s in a mob at a time
  • Diagnose on response to treatments to 150mL Calcigol/Flopak. Will get 60% or more up within an hour.

Prevention:

  • Deft, rapid handling of sheep at prelambing treatments
  • Don’t give calcium for the first half of pregnancy, unless they are being fed grain (low calcium). If you hyper-supplement them in early pregnancy their capacity to absorb dietary calcium goes down. When the load for calcium increases late pregnancy, if the parathyroid is already wound down the ewe will struggle to cope.
  • Oaten hay is deficient in calcium
  • Legume hay is a good source of calcium – if it’s 20-30% of the ration, this should be enough
  • Sheep on irrigated grass pastures, including winter cereals, need a calcium supplement
  • All cereal grain supplements should be spiked with limestone (2%) or dolomite (4%)
  • Best way to spike grain with calcium? Put the limestone into a hopper and mix with grain up the auger. Otherwise put the limestone on the top of a grain bin and let it shake down (less effective). If you have triangular feeders that have a V in the middle, place calcium there, but too much lime in self feeders can block them up. If you are trailing grain, you may need to look at providing an additional calcium supplement – the cheapest is a limestone:salt mix, or use blocks.

Vaginal prolapse is an increasingly common problem, particularly as producer’s transition from Merino to specialise in a prime lamb maternal base. There are reports of up to 3% of some flocks in some years, and occasional reports of greater than 10%.

Determinants (in estimated order of importance): age and parity (multiples); body condition; hills; foot disease.

Speculated determinants: tail length (should have the same as Merino’s, but hasn’t yet been proven); pasture type (lush, high water content); calcium/magnesium metabolism; breed differences.

Clinical signs:

  • Last month of pregnancy in fat multi-bearing ewes
  • Vagina partially everts in the last month
  • To be distinguished from prolapsed uterus (post lambing) and vaginal evisceration.

Treatment:

  • Wash them down, squeeze them up with a towel to move the blood out of them, and push prolapse back in
  • Hold in place with sutures or retaining devices
  • You may decide to induce lambing – success rate is pretty good provided you can get the lambs out

Note: a uterine prolapse occurs after lambing, is twice as big, and has lumpy bits on it

Prevention:

As we only have a poor handle on the determinants, these are recommendations only.

  • Body condition: aim to keep prime lamb ewes at CS 2.75-3.25. This will provide lots of benefits in other areas (ease of lambing, casting, ewe mortality)
  • Follow the recommendations for Merinos tail length. Leave an adequate tail for good fly control and you may help prolapse.
  • Treat foot disease to prevent pregnancy toxaemia and for animal welfare reasons, and you may help prevent prolapse.
  • Calcium supplements should be provided on lush winter cereal and ryegrass. May help prolapse, although they doubted it would have great influence.

Mastitis is primarily a problem of prime lamb flocks, particularly poll Dorsets.

  • Incidence of 2-20% in individual mobs
  • Mortality of up to 60% of clinical cases
  • For each clinical case there are 3-5 sub-clinical cases with reduced milk production.

Determinants:

  • Two major pathogens: 1. Staph aureus Mannheimia haemolytica
  • Damaged teats facilitate spread. In Australia, usually by grazing stubbles and scabby mouth
  • Probably spread between ewes by orphan lambs stealing a drink
  • Spreads well when lactating sheep are fed on grain trails
  • Genetic factors: teat shape, predisposition

Clinical signs:

  • Lumpy udder, one side can go black
  • Look for ewes with hindlimb lameness or awkward gait

Treatment:

  • Early treatment with oxytetracycline gives best chance of recovery and of limiting outbreaks

Prevention:

  • Currently no vaccine. Cannot prevent all cases but damage is limited by early detection of new cases.
  • Treat early. If possible, isolate the ewe and lamb, but this is tricky in a paddock situation.
  • Be particularly vigilant if feeding grain. Spread the grain trail out so lambs don’t have as much chance to steal a drink.
  • Do an annual cull of sheep with lumps and misshapen udders.
  • In the future genomics may identify high risk sires.

Key messages

  1. Keeping ewes at CS 2.75 – 3.25 is likely to reduce lambing diseases and may help improve stocking rates.
  2. Provide adequate feed to twinners in late pregnancy to prevent pregnancy toxaemia, and if necessary supplement with grain, even if only a trickle.
  3. Avoid over-supplementation with calcium in early pregnancy. Deft handling prelambing reduces the risk of hypocalcaemia. Provide calcium supplements to late pregnant animals on lush grass and winter cereals.
  4. Keep weight under control to reduce the risk of prolapse.
  5. Seek local advice on your current pre-lamb worm control strategy, but prelamb drenching is not a must in all situations.

To view the Ewe health challenges at lambing webinar, it will be posted on the Making More From Sheep webinar series page.

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