Sheep Farm Husbandry - Reproduction and the ram

By Dr Clive Dalton

Ram correctly serving a ewe in full standing oestrus

It’s too easy to forget about the ram. They certainly get plenty of attention during their selection and purchase, and up to the day they are joined with the ewes, but when they’ve done their work, there’s a great temptation to put them in the back paddock and forget about them. In this modern age of “disposables’ the ram fits in well; we use them and then throw them away. They deserve better.

Basic ram facts

• Ram lambs reach puberty about 6 months of age, but beware of even younger ram lambs missed at docking that can easily be fertile by autumn. Their hidden identity seems to make them more virile!
• Rams are most active in the autumn but most would mate a ewe on heat at other times of year. Mating activity, as in ewes, is stimulated by declining daylight. Rams show a kind of “rut”, but nothing as obvious as seen in goats or deer.
• Rams rarely stop to eat hence lose a lot of weight during the joining period.
• Rams start to produce a strong aroma approaching mating and the bare skin around their eyes and on their underside around front legs and crutch turns pink. They are “in the pink”. For humans with sensitive noses the aroma is similar to a Billy goat but thankfully not as strong.
• This smell comes from the grease in the wool and contains a pheromone that stimulates the ewes to ovulate and show oestrus.
• Rams with high libido may not be fertile – it’s easy to assume they are if you see them enthusiastically courting ewes.
• Courting behaviour is made up of a lot of “sniff hunting” ewes. Rams approach a ewe often from side, pawing her side with head low, rattling his tongue and giving a low bleating.

Ram 'sniff hunting' ewes. He has found a ewe on heat.

• What most farmers do is to rely first on a veterinary check of the rams’ reproductive organs and then change them after each cycle to lessen the risk of any individual being infertile. The flock is mated alright, but you never know which rams were not fully functional and you may keep them – and their progeny which is always a concern incase the defect is inherited.
• There is a big decline in the number of sperm/ejaculate in the mating period reaching the lowest levels 8 days after mating. But after the first cycle of 17 days when things quieten down a bit, the semen quality builds up again. The drop of in sperm number doesn’t seem to affect ewes getting pregnant.
• It’s always wise to use an older experienced ram on young ewes, and a young ram on older experience ewes.
• As rams are reared in homosexual groups, they may take time to learn how to mate females correctly. Find time to watch new rams working to make sure they are serving correctly into the vagina and ejaculating properly. In a good ejaculation the ram will thrust forward with all four feet off the ground.

Vet checking of rams

• It’s very important to get your veterinarian to give all rams intended for use a physical examination well before joining with the ewes.
• Sperm development takes 8 weeks so all the sperm present when the rams are joined have developed prior to mating. So it’s important to get the vet checks done at least two months before joining.
• The newly purchased rams will, if anything, be overfat and lazy because they have been fed well for sale. They should have had a thorough vet check before sale.
• Newly purchased rams should have come with a veterinary certificate to show they have been tested within 60 days of the sale and are free from Ovine Brucellosis.
• If they are going out on to hill country they’ll need exercise training. Put them in a steep paddock near the dog kennels where they will get regular disturbance or make them move every time you pass them on foot or in a vehicle.
• Some farmers put new rams in their driveway so every time a vehicle goes along (hopefully slowly) the rams are chased the full length and back again. Make sure the rams respect the cattle stop at the entrance or they’ll be gone!
• For older rams resident on the property, they may need special checking as they are often neglected after mating and may have a range of health problems.
• It is especially important to check any rams that will be used in single-sire mating mobs.
• In a standing position check the ram’s testicles through his back legs.
• The testicles should be large and hang close to the ground. They should not be tucked up near his body.
• Big testicles denote large sperm producing capacity and a scrotum circumference of 30cm or greater is considered to be adequate.
• The scrotum should feel smooth and silky and not look like crusty corduroy!
• The testicles should feel loose in the scrotum and not have any adhesions to the scrotum wall.
• Feel for a small lump at the very base of the testicle – that’s quite normal and it’s the epididymis or coiled tube for holding the sperm before they go up the vas deferens. The vas deferens is the tube the vet cuts or ligatures above the testicles when the ram is vasectomised. The epididymis should feel rubbery and not rock hard.
• Never use a ram where the testicles feel small (and the epididymis feels a similar size) and is hard. This is bad news for the ram as you would be most unwise to give him a job!
• Now turn the ram over on to his rump and check for old shearing cuts and wounds that may have been flyblown and not healed.
• Check the prepuce or sheath the penis is in. It should not be swollen or exude pus from the end as this is probably “pizzle rot”.
• Any urine stain or dirty wool around the end of the prepuce should be viewed with suspicion.
• The “button” at the opening of the prepuce has some long hairs on it – don’t shear these off as they help urine to drain away.
• With a little pressure at the rear of the prepuce, you should be able to protrude part of the ram’s penis. It has a slight bend but should not be any abnormal shape.
• Don’t panic if you see what appears to be a worm coming out the point (the glans) on the end of the penis. This is normal and for some reason the ram is unique in having such a structure which is believed to help sperm get through the ewe’s cervix.
• Check with your vet about the need for vaccinations against Brucellosis. All newly-purchased rams should have been treated.

Ram showing the 'flehmen' response after sniffing a ewe's urine

Libido and fertility

• A fit ram is capable of completing at least 10 services in 8 hours and some can do 20 or more. The concern is usually about their fertility.
• “Fertility” is the ram’s ability to produce viable sperm, and to measure it you need to check a sample of his semen. Only rams at AI centres are trained to serve into an artificial vagina (AV) so on the farm, a semen sample is obtained by electrical ejaculation. This is not always reliable as you only get a trickle out of the ram and not a good ejaculation as with an AV.
• You can also check fertility by seeing how many ewes return to oestrus after the first 17 days of him joining the flock. But if he’s infertile, you will have lost time on lambing next year.
• “Libido” is the ram’s sex drive. He may have plenty of it but be infertile, so the two may not go together.
• Some ram breeders are doing “serving capacity tests” before they decide on how many ewes to give them. The test measures how many successful services the ram achieves in a given time – e.g. a ram confined in a pen with four oestrus ewes for 20 minutes should have at least two or more ejaculations.
• This test has animal welfare implications so check with a veterinarian on the approved method. Remember also that the pen confinement may affect the ram’s behaviour.
• If your newly-purchased ram has libido or fertility problems, contact the vendor or your vet, as you should be able to claim money back or get a replacement animal. Top breeders will always replace defective rams, but you will have lost time finding out and next year’s lambing will be delayed.

Mating ratios – how many ewes per ram?

• Mating ratios have traditionally been 1 ram to 40-50 ewes, but this has probably grown with the belief that you had better have more rams than needed incase one is infertile. It’s still the standard advice today, and ram sellers don’t want to change it.
• This is terribly wasteful of ram power as many trials have shown that a good fit ram is well able to mate 100 ewes, and some have mated up to 400 ewes where maximum coverage was needed without the need for Artificial Insemination (AI).
• On large hill country blocks you have to watch out for rams that go away with a harem of ewes. The solution is to muster the sheep together at least once a day to make sure the ram or rams have contact with all the flock ewes.
• So if you had chosen to put one ram to 100 or more ewes, it’s important to have good flat or rolling country so he could easily keep in contact with the flock to be mated and not have to search gullies or scrub for them.
• Much depends on the health and fitness of the ram before the start of mating, and old shepherding lore says that rams must be “fit and not fat”.
• Most fit rams are capable of at least 10 services in 8 hours and many are capable of 20 services.
• A high-libido ram in the first days of joining always wants to give the ewe one more service, but generally after a couple of mounts and good ejaculations the ewe is less receptive for more, so the ram moves on to look for more business.
• In well synchronised flocks you often see ewes queuing up for service in the first week of joining. In this situation a ewe may only get one service as her partner has been called away!
• Ram lambs that are large enough (30-40kg) are usually given 30 ewes but if you are pushed, a lamb could mate 50 ewes over a couple of cycles.
• Research has shown that differences in ram ratios do not affect the number of twins born.

How many rams in the mating mob

• 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 can often be 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.
• However, many ewes end up being mated by more than one ram, and is often seen when mixed breeds of rams are used to find twins by different sire breeds. It has also been identified by DNA profiling.
• This can have some benefits to overall flock fertility, especially if the semen quality of a dominant ram is declining due to over work. Studies showed that returns to service were 7-10% higher in single-sire mating mobs than where many rams were present to do the mating.
• 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 for mating.
• Behaviour studies have shown that rams can be racists – in mixed-breed groups they often show a preference to mate ewes of their own breed. This was found in Merinos and black-faced breeds.

Research
Extensive research on mating ratios was done at the Invermay Research Centre by Dr Jock Allison in the 1970s.  This is reported in:
 Allison, A.J. (1975). Optimum  ram/ewe mating ratios. Proceedings of the Ruakura Farmers' Conference, 8-13.

The “ram effect”

• Old shepherds always knew that the sight and smell of a ram stimulated ewes to cycle. Not surprisingly, modern researches have proved they were right and called it “the ram effect”.
• The main reason to exploit it is to stimulate ewes to come on heat earlier than they may have done to try to get some early lambs, and to synchronise the flock to reduce the spread of lambing.
• Prior to the breeding season, most ewes will ovulate but not show heat signs. This is a “silent heat” so she is never mated.
• Joining rams prior to the start of these silent heats will stimulate ewes to ovulate within 3-6 days and show a proper oestrus 17 days later at which they can be mated.
• So timing is critical. If the ram is joined too early there will be no “ram effect”, and if joined too late the only ewes affected will be those that have not yet had a silent heat.
• To really 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. Then the ewes can smell the male “pheromones” which are in the wool grease of the ram when he starts to stink like a Billy goat. The more powerful the smell, the better the results should be.
• After about 4 days the gate is opened between them for mating to start.
• This practice is sometimes done using teaser (vasectomised) rams that are actually run with the ewes for even closer contact and actual serving.
• Teasers seem to lose their libido over time and young entire rams can have more oestrous-stimulating power when kept next to ewes through the fence.
• The other point is that it’s not always predictable what will happen as there are so many variables involved. Ewes must be in top body condition and so must the rams to get maximum benefit from the ram effect.

Shearing and dipping rams before joining with ewes

• Newly purchased two-tooth rams will have quite a bit of wool on them for the buyer to assess, so they will need to be shorn before joining.
• If you buy rams before Christmas (which is a good NZ practice), then shear them on arrival at your farm.
• This will keep the ram cool during mating and the new wool will be long enough to keep a mating harness in place.
• Shearing very close to joining is generally not recommended incase the shock affects fertility. This will not be very likely if the ram is in good condition.
• Dipping rams before joining is definitely not recommended as it may have bad effect on semen quality. This is not a well-researched area, but it would be wise to be cautious and not dip for six weeks before mating.

Using ram mating harnesses
A mating harness can be used for three reasons:

• To find out if a ram is working and which ewes he has served.
• To sort the mated ewes into lambing mobs.
• To identify barren ewes for early culling.

Old-time shepherds used to take a pot of raddle and a stick and put liberal amounts on the ram’s chest so when he mounted and served a ewe, a mark was left on her rump. This was a messy business that had to be done two or three times a week.

You had to catch the ram and wrestle him over to do the job properly, ending up covered in raddle. It was not surprising that after this indignity and the sight of the pot and stick, he became forever harder to catch!

Thankfully this all became unnecessary when the ram harness was invented. This fits around the ram’s girth behind the shoulders and holds a coloured crayon on his brisket to mark the ewe during each mount. He may leave a small mark after a false mount but usually after a good forward thrust and ejaculation, he’ll leave a good a strong crayon mark. Here are a few points about getting good results from the harness:

• Make sure the harness is properly fitted on the ram and that neither it nor the crayon holder chafe his skin, especially under the front legs.
• It has to be fitted tight to keep the crayon on his brisket.
• Check it regularly.
• Make sure you use crayons of the correct consistency. Hard crayons are for warmer conditions and soft ones for cold. Try some intermediate crayons if you are not sure, but check if the marks are clear.
• Care of harnesses is important both during and after mating. They may stretch (especially leather ones) and need more holes punching in the straps.
• Leather harnesses may need oiling which makes them very attractive to rats so good storage after mating is important.
• Store synthetic webbing harnesses out of direct sunlight.
• Using colours to separate lambing mobs

You can use two basic systems to do this:

Use one colour and draft off marked ewes.

• This eliminates the need to keep changing crayons but it means more handling of ewes in the sheep yards.
• At given intervals (e.g. 8 days which is half the cycle) draft off the marked ewes.
• Run these ewes with a ram fitted with a different coloured crayon.
• About 10-13% may return to service and those that don’t can be spot marked with a raddle on the head or back with an appropriate colour to denote the first lambing mob.

Change crayon colours

• Catch the rams after each 8-day period and change their crayons.
• A good colour sequence is:
• Start– no colour or yellow
• After first cycle – red or orange
• After second cycle - purple or green
• Third & fourth cycle - blue

Not using crayons will reduce contamination of the wool as hopefully most ewes will be pregnant soon after the ram is joined.

You can decide how many cycles you are going to accept before the ewe is considered as a cull. If not pregnant by two cycles, then she should be a candidate for culling unless there are extenuating circumstances e.g. an infertile ram.

All ewes with blue rumps are clear candidates for culling. The odd one may be pregnant but this is not worth worrying about as she will lamb so late.

What to do with the information?
If the harnesses have done the job they were designed for, then you will know which weeks the ewes will lamb in, which is very important information to plan feeding. The information is not perfect of course, so you will always be suspicious of ewes that are supposed to be in a later lambing round that are bagging up rapidly.

How long to keep a ram?

• The answer to this question is straightforward – change rams before they come round to mating their own daughters.
• So if you buy a two-tooth ram to mate ewes in autumn 2005, his daughters will be hoggets in autumn 2007 (if you wanted to mate them) and two-tooths in autumn 2008.
• If you have high Index rams that you will clearly want to use over many flock ewes in future, then you’ll have to use single-sire mating to identify his progeny or use DNA profiling.

Rams for small flocks

• Here the main problem is boredom for the ram. He mates all the ewes in the first cycle and then spends the next month at least sniff hunting them every time they move in the vain hope of some work.
• It’s no wonder he breaks out into the neighbours or out the main gate and goes to town!
• On too many small farms the quality of the rams used is dismal as they are viewed simply as something to get the ewes pregnant, and they have been bought for a give-away price at the late ram sales.
• Lambs these days are worth big money and the best way to work out what to pay for a ram is to divide his cost by the number of lambs he will sire at say $70 each. So a rubbish ram at $30 is not a good buy.
• Small farmers should consider cooperating in buying a good ram between them with some good performance records, and if convenient putting their ewes together for joining or giving the ram one cycle at each property. Late lambing ewes are not such a problem on small farms where they get more attention.
• It’s not a good idea to keep a pet lamb as the flock ram as there have been some nasty accidents by them knocking over owners and their children at mating time.

Artificial insemination (AI)

• In New Zealand, widespread commercial AI in sheep has not developed yet. It’s only been used by breeders with high-value rams and for “sire referencing. Here a group of breeders use the same ram at the same time as a “benchmark” sire, against which their own rams can be compared. This allows them to rank rams over different properties in a sire comparison or progeny test.
• Commercial AI services only develop when the sires available are of such high in genetic merit that masses of farmers want them all at the same time. They are then prepared to pay the charges and also accept all the extra on-farm work which may include some technical training in semen handling and insemination technique which is more difficult that with cows.

Basic facts on sheep AI

• The best quality semen for AI comes from rams that ejaculate into an artificial vagina (AV) and not from electroejaculation, so rams have to be trained to serve into an AV and this can require special skills.
• This is why many farmers send their rams to commercial AI stations for semen collection and also for storage. From here they order what semen they want each day.
• Normally 2-3 ejaculates are collected from a ram in a day.
• This would give enough sperm in 0.1ml of semen to mate 50 ewes.
• Because of all the extra work involved in AI, it’s a good idea to synchronise groups of ewes in the flock to come on heat together. This is done by treating them with intravaginal devices (IVDs) containing progestagen. The IVDs are left in for 12 days and after removal will come on heat 48 hours later.
• All the ewes are inseminated - sometimes called “blanket insemination” or “fixed-time” insemination.
• The other method which gives better results is called “on heat” insemination which means that a teaser ram is used to identify ewes on heat and they are brought in twice a day for insemination.
• Ewes ovulate after the end of standing oestrus, but the problem is you don’t know when they start, and the exercise has to fit in with working hours.
• When using a harnessed teaser ram to identify any on heat, bring in any ewes that were marked overnight and inseminate them that morning.
• Then in late afternoon bring in any new ewes found on heat and inseminate them. It would be a good idea to give these late ones another insemination the next morning if the teaser was still interested in them. A further insemination 10-12 hours after her first insemination can increase fertility by 6-10%.
• There are two methods of insemination. Ewes are inseminated either into the cervix (cervical insemination) or into the uterus (intra-uterine insemination). Only a veterinarian can carry out intra-uterine AI.
• With cervical insemination an experienced operator can do 50-60 ewes/hour with fresh semen, and with intra-uterine, 25-35ewes/hour is a good work rate with frozen semen.
• “Conception rate” (CR) after AI is normally lower than by natural service.
• Good operators will guarantee 60% CR for intra-uterine and 50% for cervical AI.
• Fresh semen must be used within 24 hours of collection for cervical insemination and frozen semen is only suitable for intra-uterine insemination.
• Keeping stress to a minimum is important in an AI programme. By the time a ewe on heat has been mustered, yarded, drafted, restrained for insemination and then had a speculum inserted into her vagina to light up her cervix for insemination – she may be more than a bit stressed which may affect conception rate.
• Clearly it would be most unwise to consider an AI programme in sheep without consulting your veterinarian and a professional AI service provider.