When your sheep are on heat

Reproductive potential can be impaired if ewes are used for breeding too early.

When your sheep are on heat
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Young ewes generally reach puberty between seven and 12 months of age, although there are differences between breeds, and environmental conditions such as feeding and care also play a role.

Ewes this age are not suitable for breeding immediately, however; they should have a body mass of at least 40kg or two-thirds of adult mass before they are paired for the first time.

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Animals pair during a period of ‘ruttishness’. The ewes are restless, shake their tails repeatedly and have a slightly swollen vulva. Note, however, that these signs are not as obvious in sheep as in cows.

This is followed by a ‘breeding rest’, during which pairing does not take place. These periods follow a cycle controlled by hormones. The cycle is repeated every 14 to 19 days.

Ruttishness lasts for an average of 27 hours, but can be as short as three hours in the case of young ewes. Under favourable conditions, breeds such as the Merino, Dohné Merino, SA Meat Merino and Dorper become ruttish throughout the year.

But sexual activity is generally seasonal, determined largely by the length of daylight – when the days become shorter in autumn, sexual activity increases. At the start of summer, when days become longer, sexual activity is at its lowest.

Rams can produce fertile seed when they are six to eight months old but are generally not used for servicing before 18 to 24 months. Their sexual activity is not as seasonal as that of ewes, although it is at its highest in autumn.

Observation of heat
One of the best indicators of ruttishness is the presence of rams among ewes. Ewes on heat seek out rams and stay close to them, repeatedly rubbing their necks or bodies against the rams. Teasers, or rams with aprons, which prevent penetration, can be used to identify ewes on heat.

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If constant observation is not possible, markers on the chests of rams can be used to identify ruttish ewes, as the marker will rub off onto the ewe. A mixture of ochre dye and margarine can be rubbed on the rams’ chests if marking equipment is not available.

Methods of servicing
Three main techniques are used:

  • Group or flock pairing, where one or more rams are used to service ewes.
  • Manual pairing, where ruttish ewes are identified by teasers and then paired individually with a specific ram.
  • AI, where ruttish ewes are inseminated with seed.

Optimal flock management
Flock management should be aimed at increasing sexual activity, maintaining rams and ewes in good condition to ensure successful servicing:

  • Provide rams with supplementary feed before and after servicing.
  • Give ewes stimulants from three weeks before servicing to a month after, taking into account their condition.
  • Test rams for fertility and servicing ability before pairing, and walk them 1km to 2km every day at a fast pace for exercise.
  • Place teasers with ewes two weeks before servicing to stimulate sexual activity, if necessary.
  • Complete immunisation and parasite treatment a month to two weeks before servicing.
  • Crutch ewes with wool growth of longer than six months.
  • Enough rams should be used in flock pairing (3% to 4%).
  • Pair young ewes separately.
  • Continue pairing for at least two ruttishness cycles (34 days).
  • Use small camps with sufficient grazing or feed, water and shade.
  • Keep the ewes calm for four weeks after servicing.

Source: Elsenburg infopak by TS Brand, B Aucamp, J Botha and A Kruger.