July 12, 2010

NZ Sheep Husbandry - Managing ewes with multiple lambs

By Dr Clive Dalton

Pregnancy scanning
Pregnancy scanning (at around NZ50c/ewe in New Zealand) has been a great innovation to help farmers improve the management of pregnant ewes. Scanners are now doing more small flocks if the opportunity arises between large flocks, more as a service than a money maker.

The good thing is that after scanning, at least you know which ewes are carrying multiples (twins and triplets) and will need the best feed and special care. And you don’t waste feed and time on ewes with singles and empty ewes which you can get rid of immediately.

Before scanning - old shepherd's tricks
Before scanning was developed, we had to guess if a ewe was carrying multiples by the size of her belly. Some old shepherds would palpate the ewe's belly and try to feel how many lambs were there.

Another trick was to drive the flock slowly for a distance along a race, and then cut off the ewes at the back of the mob that walked the slowest as being ‘heavy laden’ with lambs, as the most likely to have multiples. These were not very accurate techniques but it was all that we had.

Foetal demands
The demands of the growing foetus are not a great burden on the ewe in the early stages of pregnancy, but in the last three weeks the lambs really start to grow, drawing heavily on the ewe’s body reserves, and increasing the strain on her body.

Triplets are clearly the biggest drain, as they (and twins too) start to take up space inside the ewe’s abdomen, which clearly has limits to how far it can stretch. This is the reason usually given for the ewe’s drop in appetite in the last weeks before birth, but it’s also believed to be hormonal which seems highly likely.

The general rule is that in the six weeks before lambing, twin-bearing ewes need 25% more feed and triplet-bearers need 44% more than ewes carrying singles. So multiple-bearing ewes should be fully fed and not lose any body condition in the last five weeks of pregnancy.

Even yarding such ewes for 2.5-3 hours in the last weeks can cause a build up of ketones and risk metabolic problems. It is said to depress lambs' vigour and drive to suck when born.

Hazards to health

A lucky triplet, its mother waiting for it to get what its twin mates have left.
As lambs get bigger, competition for the two teats gets more aggressive
  • Feed intake check. A sudden cold snap can cut the feed supply and cause added stress, so the ewe has to draw even faster on her body fat reserves. She ends up with metabolic problems involving excess ketones in the blood causing ketosis or pregnancy toxaemia – sometimes called twin-lamb disease, as it only happens with multiples. Ewes can die very quickly and require instant injections of glucose. Ewes can also have sudden shortages of calcium causing milk fever or of magnesium causing grass staggers.
  • Bearings. Here the vagina, and worse still the uterus is pushed out or everted. This is a really nasty prospect to deal with, and it needs urgent veterinary attention, as the risks of infection are high. The pressure inside the ewe from the growing lambs is blamed, along with pressure from a full rumen if the ewe has just eaten fresh green feed.
  • Getting cast. Ewes with large expanding bellies can often get on their backs and cannot get back on to their feet again. This often happens if they lie and rest in a hollow or start rubbing because of lice. They can very quickly die of bloat in this position as they cannot belch.

Lamb mortality
It’s important not to assume that the scanning percentage (number lambs scanned/100 ewes joined with the ram) will be your ‘lambing percentage’ (measured as number lambs born/100 ewes joined).

We now know that there can be a 15-20% loss between scanning and birth. In the early days of scanning, ‘scanner error’ was blamed for this late foetal loss, as most loss of embryos always occurs in the first weeks after conception when implantation if taking place.

In recent years, we have had to accept this figure of scanning-to-lambing loss as today’s operators are highly accurate and cannot be blamed. The sheep has an ability to absorb foetal lambs right up to lambing, with the very late ones seen as mummified lambs.

Few farmers count dead lambs at birth as it’s too depressing, but they always have an accurate count at docking. So if you compare scanning percentage with docking percentage (number docked/100 ewes joined), you find the figure is frightening and can be as high as 40% - made up of 20% before birth and 20% after (as ‘perinatal mortality’ in the first 3 days after birth).

It seems to be nature’s way of keeping populations under control and ensuring ‘survival of the fittest’. Buy it’s very frustrating for the shepherd and costly for the nation.

The battle to save lambs
At the Whatawhata Hill Country Research Station, in the 1970s to 1980s, we researched the causes of lamb mortality (D C Dalton, T W Knight, D L Johnson. 1980. NZ J. Agric. Res. 23: 167-173) looking for causes and solutions, and others have repeated this work since – all with the same outcome.

We know what lambs die of (starvation/exposure and dystocia or difficult births), but in the last 20 years have not come up with practical solutions to prevent lambs dying around birth, other than to provide shelter and lamb on flat paddocks. Shepherds have known this for hundreds of years!

Why do lambs die?

Dead twins - note one is bigger than the other. The bigger one shows
signs of dystocia by its swollen neck

When you post-mortem lambs in the first three days of birth, here are a few basic signs to provide some clues to the cause of death. Them more of these you can see, singly or in combination, then the more accurate the conclusion. The most common single signs are:
  • A lamb under 3.5kg, especially it’s a twin or triplet, will have died of exposure/hypothermia.
  • A lamb over 5.5kg, will most likely have died of dystocia.
  • If the head is large and swollen, the neck swollen neck, and a blue swollen tongue protrudes from its mouth, then dystocia is certain.
  • No milk in stomach – it clearly had not suckled so assume starvation probably through mismothering.
  • Pads still on feet –it hasn’t stood up and walked, so assume mismothered.
  • Membrane over nose would be suffocation.
  • Some birth membrane still on body, most likely it has been licked so assume mismothered.
  • Lungs not inflated – it has not breathed. Check if lungs will float in water then it has breathed.
  • Kidney fat brown – fat not mobilised so died soon after birth.
  • Kidney fat white – fat has been mobilised so probably lived for few days.
  • Malformation (e.g. no rectum) may be cause of death a few days after birth.

‘Starvation/Exposure’ was always lumped together in our early research, but now researchers are using the term ‘Starvation/Mismothering/Exposure complex’ (SME). These terms illustrate how little we know, and how much guessing still has to go on to predict what lambs die of at birth.

Birth weight is critical

Dead lamb - born a multiple under 3.5kg

The main finding was that birth weight was critical for survival, and subsequent research has come to same conclusion. The best birth weight was around 4kg, but of course it was controlled by how many litter mates the lamb had as this caused the wide range found.

As mentioned above, if a lamb is under 3.5kg at birth (which is very common in triplets), then survival chances are low due to starvation/exposure, and similarly above 5.5kg (most often singles) risks are high due to dystocia. But then multiples can die of dystocia too if more than one lamb gets stuck in the birth canal.

An exhausted ewe after lambing triplets, probably a week early. The two larger lambs (weighing 2.2kg and 2.8kg) have got to their feet and found the teat. The tiny triplet (weighing 1.2kg) is struggling to stand and has not had a feed. It's going to be left behind with poor chances of survival.

Controlling birth weight
This is the problem – we don’t know how to control birth weight of the lamb.
Feeding the ewe during pregnancy is the obvious way to do this – in theory, but research over the years has shown that it to be a very hit and miss affair. Some trials showed positive responses but others failed to do so.

In the past with less fertile NZ Romney sheep when a good lambing percentage was 100% docked, we had to reduce feed intake in the last three weeks of pregnancy to avoid dystocia in the many single lambs born, but it’s not a wise move now with today’s highly productive sheep, as it may trigger major health problems. Today’s advice is to keep ewes on a level plane of nutrition right through pregnancy.

The ability to stand up

This triplet has just stood up 4 hours after birth and is very weak and
wobbly on its feet.Its chances of survival are low.

How quick a lamb is able to get up on it's feet is vital to survival, as it will then start teat-seeking and hopefully get a feed of colostrum. Research has shown that if you can reduce the time a lamb gets up from 45 mins down to 15 mins, there's a 49% greater chance of it being alive at weaning. This ability to 'get up and go' is very much related to the lamb's fat stores at birth.

Easy-care sheep

With the low profits from sheep over the last 30 years, intensive shepherding of ewes at lambing was not economically viable, so breeders solved the problem by selecting for ‘easy-care’ traits where ewes with lambing problems were culled.

Shepherds kept away from ewes at lambing and any ewe with problems died. This had bad animal welfare implications so the policy was changed to inspection of ewes at lambing, and marking for culling any ewe that had to be assisted at lambing. Her ewe lambs were marked for culling too. It’s been very successful.

This approach coincided with an massive increase in fertility of the New Zealand ewe flock through selection and importation of fertile breeds such as the Finn and East Friesian, so ewes were selected that could lamb multiple with ease, bond and mother them, and then rear them to weaning.

Triplet problems

Will this triplet patiently waiting be given a chance for a
drink before the ewe moves on?

As the average fertility of the national flock has increased, the number of triplets has increased, and these are causing challenges under out outdoor low-labour and easy-care lambing systems. Some ewe flocks now have 30% of ewes having triplets and 15% of hoggets lambing with triplets too.

Now that we have more lambs been born because of the triplets, it has increased the number of lambs weaned, but the mortality rate has not changed. So from a national viewpoint, it’s hard to ignore a 40% overall lamb loss between scanning and weaning, realising the export value of these lambs. It’s an awful waste still waiting for an answer.

Intensive shepherding for small high fertility flocks
In small flocks it’s worth providing all the help you can. Here are some suggestions:

  • Get all the lambing gear sorted a month before the first lambs are due. Pay special attention to medications for metabolic diseases like pregnancy toxaemia (low glucose), grass staggers (low magnesium) and milk fever (low calcium). You can get all three preventatives in the one bottle or sachet complete with needle. Talk to your vet.
  • Make sure you know how to use the gear, especially how to put a feeding tube down a lamb’s gullet without filling it’s lungs with milk and drowning it.
  • Treat the ewes quietly before lambing, but some gently exercise is good for them. Do this by shifting them between paddocks.
  • If you have a dog, it must be under full control at all times, and the ewes are used to seeing in with you. All other dogs should be kept away from the flock.
  • It’s always better to leave newly-lambed ewes on their birth site till they are fully bonded with their lambs, but with triplets, weak twins or a ewe that’s not mothering all her lambs, it’s more important to get them under cover for their first night.
  • Get them into shelter as soon as they’ve licked their lambs and the lambs have stood up and started teat seeking. Keep them in this shelter, certainly for their first night after birth.
  • The best idea is to make some simple ‘lambing pens’ in the paddock from hay bales or small gates with a cover over half the top.
  • Learn a few tricks to get the ewe to follow one or two lamb while you keep moving towards the pen carrying the others. The last thing the ewe wants at this stage is more stress.
  • The ewe will want to rush back to her birth site where the smells of her burst waters are very attractive, so keep the lambs close in front of her as you move backwards, bleating like a lamb to attract her to the lambs.
  • Once the ewe is into a pen, then it’s easier to check her udder and milk supply, and it saves the trauma of catching her in the paddock.
  • If she's too heavy to turn over, then you can block her up against the side of the pen and milk her from the side like a cow.
  • This will clear the wax seal in the end of the teat, which a weak lamb takes too long to suck out.
  • By squirting some colostrum from a teat down each lamb’s throat immediately after birth, you know all three have had that first vital feed.
  • It’s no good just standing, watching triplets teat-seeking in the paddock with the mother fussing around them, especially if she hasn’t seen lambs before – and assuming they’ll all get a feed. On a wet night, the shock from 29C inside the ewe to 5-6C in driving rain will kill them with hypothermia in less than half a hour.
  • In a mothering/teat seeking mixup, nobody gets a decent drink in the first couple of hours, which can be fatal for one or more of them. The biggest lamb will find the teat and the weaker ones will not.
  • Triplets are not always the same birth weight which is critical in survival. Also there may be a delay between the first and third arriving, so the first lamb if big and strong has got on to its feet, found the teat and emptied it. The mother may give it all the attention so the late born triplet has little chance.
  • At birth, use different raddle marks on each triplet set, so if you see lost lambs in the paddock blaring for their mums, then you know where they belong.
  • The best way to catch and hold triplets in the paddock e.g for inspection or tagging, is by using a fishing landing net. After you've caught them, they can stand with the ewe being able to see and smell them.
  • Watch out for ‘burglar ewes’ that will bond with newly-born lambs from other ewes, before they have lambed themselves. They can cause great havoc among twins and triplets.
  • Keep a close eye on the most popular lambing spots in a paddock, as you’ll find it hard to sort out which are a ewe’s own lambs when they have lambed together. It’s a good reason to spread ewes out before lambing.
  • Popular lambing spots can get very dirty too, so it’s often wise to fence them off half way through lambing. Applying iodine to fresh navels is very important.
  • Learn to recognise when a lamb is full. Press upwards on its tummy in front of its back legs and it should feel like a drum. If it’s not inflated, then the lamb has not fed and you need to ‘tube it’ with some good quality lamb colostrum replacer.
  • For starved lambs, take them inside, give them a feed of colostrum and wrap them in an electric blanket to maintain a constant heat. Dunking them in a bath of warm water used to be the trick, but the water soon cools. If you do try this, dry them and wrap them in the blanket.
  • As the ewe’s milk supply starts to build up, watch out for lambs getting blocked up with yellow faeces. This happens often in windy drying weather.

Decisions – to remove or leave triplets on the ewe
There’s no doubt that today’s high performance ewes have enough milk to feed triplets, but there are other points and decisions to be made. Here they are:
  • When do you want to market your lambs? Triplets will rarely have reached a market weight by Christmas in New Zealand’s North Island. So they’ll end up as store lambs, and they’ll be on the farm right through the dry summer period needing money spent on them, worms, lice, blowfly treatment and maybe more. You may not get rid of them till autumn or early winter.
  • So if you want to have the bulk of work over by Christmas, you’ll need to remove a triplet. Then you have to decide what to do with the it. You can:
  • Euthanase it if it’s very small and weak.
  • Mother it on to a ewe with a single – accepting the work involved.
  • Rear it yourself on milk powder at financial loss if you include labour.
  • Give it away as a pet lamb to have it returned when the kids are sick of it.
  • If you leave triplets on their dams, best practice is to run them with twins as a stray has a greater chance of sneaking a feed from a confused ewe than if they are mixed with singles – where ewes know their lambs and defend them at all costs.
You also need to be alert to lambs appearing to have lost their mothers in the paddock, at about day10-13 after birth. Farmers who have noticed this say that it seems that by this time, two lambs have established a strong sucking order each with their own sides, and will not let the third lamb in. After the two have sucked the ewe moves on to prevent further sucking, and the third lamb misses out – again. Eventually the ewe seems to decide that two lambs are enough, and stops worrying about her third one, being happy to leave it behind.

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