- 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 liveweight.
- Only about 20% of farmers mate their ewe lambs. 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 range) and will be on heat for about 4-8 hours.
- Signs of oestrus in the ewe are not very obvious compared to cattle:
- 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.
- Pregnancy in the ewe is five months.
- 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 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, or by changing 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.
- As rams are reared in homosexual groups, they may take time to learn how to mate correctly. Take time to watch new rams working to make sure they are serving correctly 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 ewe often from side, pawing her side with head low, rattling tongue with low bleating.
- Mating ratios of 1 ram to 40-50 ewes seems to be normal. Ram lambs that are large enough (30-40kg) are given 30 ewes. But a good fit ram will easily mate 100 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 than mating. Fighting also leads to injury which rarely recovers 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 ewes that have come to him and are waiting. But it’s just his luck if by 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 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 the ram to stimulate ewes to cycle. It’s recognised as "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 the party starts.
- This practice is sometimes done using teaser (vasectomised) rams that are actually put in with the ewes for close contact and serving.
- Teasers seem to 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.