Breeding age of ewes

Determining the optimum age for first breeding maiden ewes isn't always straightforward—there will be gains in some areas and losses in others.

For example, delaying maiden ewe breeding for 12 months will result in higher wool production from the ewe, but this needs to be carefully weighed-up against the potential for fewer lambs over the ewe's productive life cycle.

Maiden ewes must be at the target liveweight and on a rising plane of nutrition to be successfully joined.

Minimum body weight

Maiden ewes need to attain a minimum body weight of about 40 to 45kg to reach sexual maturity, and generally at this weight have a conception rate of about 80%. Heavier ewes should do even better.

A slight difference in weight, just by a few kilograms, reduces the conception rate by as much as 40%.

If a ewe is lighter than 28kg they will not conceive, so ewe lambs born late in the lambing period may have difficulty reaching the required breeding weight in the following year.

Meat sheep breeds (crossbreds, composites and Dorpers) tend to reach the target weight quicker than Merino maidens. These breeds can be joined as early as 7 to 9 months while Merino ewes may need 9 to 10 months before they reach the required weight for first joining.

Delayed joining

In a well-managed breeding program, the average ewe is joined 5 times, first at about 1.5 years and last at 5.5 years.

Delaying the first joining will not increase the productive breeding life of the ewe. It will, however, reduce the number of joinings possible during this period to 4, and reduce the total average number of lambs per ewe to 3. This means that about 50 fewer lambs will be produced per 100 ewes in their productive life span.

Joining maidens before the 12–18 month mark is estimated to increase returns when based on a conservative lambing percentage of 60% lambs weaned per ewes joined.

Benefits of early joining of maiden ewes when best management advice is followed:

  • increased profitability through increase in lambs born per year
  • increased lifetime reproductive performance
  • faster genetic improvement with selection of progeny born to ewe lambs reducing the generation interval.

However the benefits of delaying maiden ewe joining include:

  • improved wool production
  • increased growth rate
  • higher final saleable value for their meat.

Wool production

Ewes that do not have a lamb will produce a heavier, higher quality fleece. Lambing places additional demands on the ewe and wool production is generally less.

The effects on wool production will be similar for ewes that lose their lamb after birth. However ewes that conceive, but do not carry their lambs to term, will lose little in wool production.

Mothering ability

Although mothering ability is heritable, it's something that is largely learnt through experience.

Ewes on their first lamb, regardless of age, are generally poorer mothers, and a significant proportion of lamb losses that occur after birth can usually be attributed to this inexperience.

Mismothering can be compounded by difficult births and starvation, caused by:

  • joining maidens with rams that are too large
  • insufficient feed available at lambing.

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