Joining length for rams and ewes
The joining period should be long enough to give all your ewes a realistic chance of getting in lamb, but short enough to allow other management practices, such as shearing, crutching and weaning, to be carried out on time.
Controlled joining can be anything from 6 weeks to 6 months. When working out the optimum length of joining, it's important to consider the number of joining opportunities your ewes will have to cycle.
Under ideal circumstances, good conception rates can be achieved from a 6-week joining. However, if your maiden ewes are in a poor condition or lambs have not been weaned early enough, a period of up to 10 weeks may be necessary.
Ewes' ovulation cycle
During a normal joining, ewes will exhibit oestrous peaks at about 16-day intervals. In theory, a ewe need only cycle and ovulate once in order to conceive. However, where large numbers of animals are involved, in a big paddock, the theory needs to be modified to achieve a practical result. Some ewes may not cycle at all until several weeks after rams are introduced. Others may either not conceive at their first service, or may not mate during their first cycle.
With an approximate time of 3 weeks per cycle, ewes that cycle but don't conceive during the first, second or third weeks of joining, will have another chance to do so in the fourth, fifth or sixth weeks respectively.
If ewes have their first cycle during the fourth week (or later) they will only get 1 opportunity to conceive. This can often occur with maidens and ewes that are in poor condition. The chance of conception will also be reduced if lambs are not weaned early enough to allow ewes to recover.
Minimum joining period
A minimum joining period of 6-weeks for rams and ewes will be successful if:
- feed quality is good
- ewes are in good condition
- ram fertility and libido are high
- management activities (such as weaning) have been carried out on time and to a high standard.
These conditions are most likely to occur for a well-managed autumn joining but will rarely happen in spring/summer joinings.
Maximum joining period
Joining rams and ewes for longer than 3 months is not advisable as lambing will interfere with other management activities such as shearing and crutching. There will also be a large variation in lamb size at marking, with the older lambs being almost too big to handle and the younger lambs too small to mules (if it is required).
A long joining period will mean that at weaning, the younger lambs will have a reduced chance of survival. The tendency is then to delay weaning and allow them to grow out, which in turn interferes significantly with the following year's joining.
A 10-week joining is considered a good compromise between the minimum and maximum joining periods. With a 10-week joining, your ewes will have the opportunity to cycle 4 times. If good conception rates cannot be achieved from a 10-week joining, regardless of the time of year, it will be due to problems elsewhere within your management system. Even during dry years, a 10-week joining period will allow your ewes, including your maidens, an opportunity to get in lamb.
By using the ram effect, most of your ewes will cycle during week 1 of joining. Those that don't conceive will have other opportunities at weeks 4, 7 and 10. Even in dry years, this will give all your ewes (including your maidens) ample time to get in lamb. It's still possible that with a 10-week joining there will be a spread in lamb size during marking and weaning, but it will be manageable.
A 10-week joining period will result in a 10-week lambing. This allows for a gestation period of 21 weeks, and leaves 11 weeks in the year between the end of lambing and the start of the next joining. If management is good and your ewes lamb early, it will also allow lambs to grow out and be weaned for 4-6 weeks before the next joining.