Animal behaviour and welfare: Sheep Part 2

SHEEP BEHAVIOUR BASICS: PART 2

Reproduction: Lambing: Lamb survival: Fostering

By Dr Clive Dalton

The ewe

• Sheep are seasonal breeders and ewes are stimulated to cycle by the declining daylight pattern in autumn.
  
• Female sheep reach puberty at about 6 months old, depending on breed and live weight.
  
• Only about 20% of farmers mate their ewe lambs and there is no problem getting these hoggets to come on heat if they have been well fed, and are a minimum of 35-40kg by 6-7 months old.
• Ewes come on heat every 17 days (14-20 days range) and will be on heat for about 4-8 hours.
• Pregnancy in the ewe is five months (154 days)

Signs of oestrus in the ewe
These are not very obvious compared to cattle. Here are some:

• The ewe will seek out a ram.
• She will sniff him and chase after him.
• She will crouch and urinate when a ram sniffs her side or genital area.
• She will fan her tail when the ram sniffs her.
• When the ram is preparing to mount, she will turn her head to look at him.
• Ewes do not mount other ewes as in cattle.

Ram has found ewe on heat. She stands still, looking around at the ram, tail fanning, ears pricked. She is waiting to be mounted.

The ram

• Rams reach puberty by about 6 months of age, but beware of younger ram lambs that miss docking as they could easily be fertile by autumn.
• Rams are most active in the autumn and are stimulated by declining daylight. They show a kind of "rut", but nothing as well developed as seen in goats or deer.
• They start to smell very strongly like a Billy goat approaching mating and the bare skin around their eyes and on their underside around front legs and crutch turns pink.
• This smell comes from the grease in the wool and contains a pheromone that stimulates the ewes to ovulate.
• Rams with high libido may not be fertile so fertility can be checked by a semen test using electro-ejaculation. This does not deliver the same quality of sperm as a good strong natural ejaculation but it is an indicator.
• To avoid problems, farmers usually change rams after each cycle to lessen the risk of a ram being a dud.
• Counting the number of mounts on a restrained ewe over time can also indicate libido, but seek veterinary advice on the ethics of this practice.
• It's wise to use an older experienced ram on young ewes and a young ram on older experience ewes. But some farmers argue the opposite and reckon the extra libido of young rams stimulated the young ewes better.
  
• As rams are reared in homosexual groups, they may take time to learn how to mate females correctly. Take time to watch new rams working to make sure they are serving correctly into the vagina and ejaculating. In a good ejaculation the ram will thrust forward with all four feet off the ground.
• Courting behaviour is made up of a lot of "sniff hunting" ewes. Rams approach a ewe often from side, pawing her side with his head low, rattling his tongue and giving a low bleating.

Ram 'sniff hunting' ewes.

• Mating ratios of 1 ram to 40-50 ewes is normal but a good fit ram will easily mate 100 ewes. Ram lambs that are large enough (30-40kg) are given 30 ewes.
  
• Having a surplus of rams in the flock may be a good insurance against infertility but they will spend more time fighting and establishing dominance and may miss ewes on heat. Fighting also leads to injuries which rarely recover before the end of mating, so an expensive ram is often a write off.
• In large mobs where many rams are used, the dominant rams do most of the mating, chasing the less-dominant away. Practice makes perfect, so these dominant rams, getting more practice do the job quicker and so get more work.
  
• The subordinate ram may get a service when the dominant one has moved away to find more fresh ewes, or with ewes that have come to him and are waiting. But it's just his luck if by the time it's his turn, the ewe is starting to go off heat and won't stand.
• Rams can be racists - in mixed-breed groups they often show a preference to mate ewes of their own breed.
  

The "ram effect"

• It's an old practice to use the sight and smell of a ram to stimulate ewes to cycle. It's called "the ram effect".
• To exploit it ewes are first isolated from sight, sound and smell of all rams for at least 2-3 weeks before joining.
• Then both sexes are put in adjoining paddocks to view and smell each other through the fence.
• After about 4 days the gate is opened between them and they are joined.
• This practice is sometimes done using teaser (vasectomised) rams that are actually put in with the ewes for even close contact and serving.
• Teasers lose their libido over time and young entire rams seem to have more stimulating power through the fence. The little bit of extra frustration seems to help.
  

Lambing

Ewe behaviour prior to lambing

• A few hours before lambing, a ewe will move away from the main flock to find a quiet birth site.
  
• Particular areas of lambing paddocks such as hollows or hill tops can be very popular spots and many lamb mix-ups and mismothering can happen here.
  
• It may be necessary to fence these areas off after a while when they get muddy. This will avoid a great deal of extra work and frustration for the shepherd.
• Ewes heavy in lamb become very quiet and near lambing are more vigilant and graze less. This restlessness lasts until the ewe finally selects a birth site.
  

On the birth site:

• The ewe paws the ground.
• She keeps turning round and round.
• She lies down and gets up a lot.
• Her waters burst and she gets up to smell the ground where it fell.
• Then after labour contractions the lambs will be born.
• The ewe then gets up and licks the lambs.
• The lamb may be finally delivered with the ewe standing.
• The ewe produces the afterbirth.
• She will remain on the site till the lambs have suckled.
• Ewes vary in the time they spend on the birth site.
• Old experienced ewes will move off as soon as the lambs have suckled and can move with her. These ewes with good maternal instincts and experience seem to be able to count and will not leave their lambs behind - going back to gather up stray twins or triplets. They stand with head down giving a low bleat and constantly nuzzling the lambs.
• Younger ewes with no previous experience will stay longer on the birth site, as they have the novelty of a lamb to deal with. If disturbed then these sheep panic more easily leading to lamb neglect.
• It's good practice to leave newly lambed ewes alone on their birth site, and only move them after a couple of days when they have clearly bonded and moved off to another area of the paddock themselves.
• Shifting ewes or lambs in the middle of the birth process is a disaster and will lead to mismothering of lambs.
• It's a good idea to spot mark multiples at birth and then leave them alone. This helps to ensure correct mothering later.
  

Burglar ewes

• Often a ewe that has not lambed will steal a lamb from a newly-lambed ewe as her maternal instincts have got out of phase.
• She can cause enormous disruption in a lambing paddock as you often don't know that she hasn't lambed until the day you find her with a lamb a few days old, and then a new one!
• The only cure is when you discover the trick is to shut her out of the lambing paddock until she has lambed or if she is near lambing, lamb her.
• Often you are tempted to put her in the killer's paddock when you discover what she's been up to and the trouble she has caused to your records!
  

Mothering and lamb survival

• Sheep are classical "follower species" where the lamb follows the ewe most of the daylight hours and right up to weaning.
• The lamb starts following movement immediately it is on its feet after birth. You'll see a very young lamb follow the shepherd, the dog or the bike, and this can lead to mismothering.
• Lambs learn to recognise their mothers by sight by about 3 days of age.
• Multiple births are common in sheep. Finnish Landrace sheep can even have litters up to 7-8. As the ewe has two teats, there is high mortality in these highly fertile breeds unless the lambs are artificially reared.
• Breeders once started to select sheep with four functional teats but this has not got very far.
• Good lamb survival depends on the ewe licking the lamb and the lamb finding the teat immediately after birth.
• Teat seeking behaviour is important. The lamb has got to be determined to get on its feet, start nuzzling the ewe to find an area of bare skin and find a teat to suck on.

A good ewe will stand still while the lamb is seeking the teat

• Some lambs find the skin under the front legs and waste time looking for a teat there before moving to the rear end of the ewe.
• A good ewe will encourage the lamb to move to the rear by standing still and nuzzling its rump and anal area.
• Inexperienced young ewes will not stand still and turn round to lick the lamb all the time. Lamb dies of starvation often through this overzealous mothering.
• Once the lamb has found the teat it will stand with head down reaching below the ewe, pushing upwards and once on the teat, wagging its tail while suckling. But don't assume that a lamb wagging its tail has always found the teat - check that its under belly is rounded and full of milk.

Lambs in the first 3 days :

A nice sunny sheltered spot to aid survival but where's its mother?

• Dystocia of single lambs that get too big and stick in the birth canal.
• Death of small multiple lambs that have not sucked.
• Lambs that die from wet and cold - hypothermia.
• Multiples left behind to starve when ewe takes off with one lamb.
• Lambs that suffocate as membranes around lamb have not broken at birth.
• Lambs that follow other ewes and are rejected. Not found again by own dam.
• Lambs that have slipped down steep hillsides away from their birth site.
• Lambs that die from haemorrhage as ewe has chewed the navel or tail
  

Bonding

• First sound then sight soon reinforce the ewe/lamb bond that was built initially on smell. The ewe recognises the lamb's bleat, and the lamb learns the ewe's call.
  
• This is important as lambs get older and spend time away from the ewe for short periods, e.g. with other lambs.
• Lambs show great play behaviour especially approaching dusk when they race along fences and play "king of the castle". They can often fall down holes and drown in water troughs during this activity.
• When danger is seen, the ewe first calls the lamb then checks its approaching identity by sight.
  

Triplet problems

A good ewe will recognise she has more than one lamb and mother them all

• The increasing fertility in modern sheep breeds has led to higher numbers of triplets and quads in commercial flocks.
• As a ewe only has two teats, inevitably there are higher death rates in these multiples and if they are reared, either on the ewe or artificially, it leads to many smaller lambs at weaning.
• Some farms now get up to 40% triplets and once litter size (number of lambs born/100 ewes lambing) gets over 2.2, an increasing number of quads are born which the ewe cannot rear.

With quads, at least one lamb has to be removed

• With triplets, observant farmers have noticed that between 10-15 days after birth, the ewe decides that she cannot feed all her lambs so she starts to leave one behind.
  
• The two that get to the udder first can soon drink all the milk so when it's the turn of the third lamb, there is no milk left. The neglected third lamb is found motherless in the paddock and will die if not removed and fed which may not be economic.
• Advisors recommend that ewes with twins and triplets are run together and ewes with singles grazed on their own.
  
• This is because there’s a better chance of multiples moving between dams than a ewe with a single accepting a stray multiple lamb.
  

Reviving starved lambs

• If a lamb is badly chilled and not had any colostrum, chances of survival are poor.
• Colostrum is vital – and it will have to be tube fed.
• Wrapping the lamb in an old electric blanket works best. It stays at constant heat.
• Bathing a starved lamb in a blood-heat water may work followed by placing them under a heat lamp. In the batch as the water cools, this effectively finishes the lamb off.
• Make sure you don’t overheat the lamb under the heat lamp.
• Vigorous rubbing with an old towel helps circulation followed by the heat lamp.
• Whisky or brandy was a traditional lamb “saviour” but it’s more effective if the shepherd takes it!
  

Fostering

A lamb on its own calling out and not full. Find its mother or else it could mean fostering or artificially rearing it with all the work involved

• Bonding of the ewe and lamb is very rapid at birth - it only takes a few minutes. Once the ewe has smelled the lamb she will not take a lamb that smells differently.
• To foster lambs on to ewes, there are a few tricks but realise that some ewes are more determined than others not to be fooled.
• To add a lamb to a ewe that already has a single, have the lamb ready and cover it in the ewe's birth fluids so both lambs smell the same. The fostered lamb will be more active so make sure the ewe licks her own lamb well and it gets a drink. It's best to artificially feed it to make sure it gets enough colostrum.
• For a ewe with a dead lamb, skin the dead lamb and make it into a suit with holes for legs to fit on the fostered lamb.
• Use strong smelling oil or commercial product to put on lamb and up the ewe's nostrils. This is not always effective.
• Put the ewe in close confinement or in a headbail and leave the lamb with her till she accepts it. This may take a few days and some ewes will win the battle with you and never take the lamb.