Joining sheep

Critical factors for a successful joining include:

• Seasonality
• Ewe nutrition
• Ram health

Day length and breeding cycle

Generally, sheep are ‘short day’ breeders, meaning they tend to naturally cycle best as day length becomes shorter. Different breeds vary in their seasonality, with British breeds such as the Border Leister and their crosses being much more seasonal the Merino or Dorset - as indicated in the following chart.

Figure 1 - Indicative pattern of natural cycling activity in various sheep breeds throughout the year (Source: O’Halloran 2007). 

By the end of January, most ewes are cycling spontaneously every 17 days and a joining period of two cycles or five weeks is recommended.

The challenge lies in joining sheep through spring and early summer, particularly in British breeds and their crosses. During this time there is a lower percentage of ewes naturally cycling. There are several options for improving joining outcomes during this period.

The ‘ram effect’

Complete isolation of ewes from rams before suddenly re-introducing rams will have the effect of stimulating ewes to begin cycling. For this to work successfully, ewes must not have any contact (sight, sound or smell) with rams for at least one month before joining commences. A distance of at least 1km from any ram (including neighbours’ rams) is recommended.

Either rams, testosterone-treated wethers (known as ‘teasers’), or vasectomised rams will produce the pheromones needed to achieve the ram effect.

Usually, the ewe’s initial stimulated cycle will be a ‘silent heat’. For this reason, it’s a good idea, if feasible, to use teaser wethers or vasectomised rams during those first 14 days. This prevents entire rams from becoming frustrated and injuring each other while waiting for the ewes to come into standing heat.

Example use of teasers for a natural mating program

1. Inject selected wethers with testosterone seven days prior to commencing teasing.
2. Tease for 14 days.
3. After 14 days, introduce rams to ewes at 2 per cent and join for 35 days (teasers can be removed or left with mob – ram-like behaviour from testosterone only lasts 3-4 weeks).

*It is important to note that testosterone-treated wethers cannot be sold – they can be slaughtered on farm or kept for teasing in subsequent years.

Benefits of using the ‘ram effect’ for joining

• Most ewes are cycling when the entire rams are joined
• The joining and lambing will be more compact
• The lamb drop will be more uniform in age and size at marking, weaning and first shearing

Ewe nutrition and body weight

• Nutrition and condition score are the greatest determinants of ewe reproductive rate.
• Check ewe condition at least a month prior to joining to assess if feeding is required to maintain their condition.
• Check ewes for low condition, udders, poor feet and mouth condition, and cull appropriately.
• Aim to have ewes in condition score 3+ during joining.

Monitoring fat score when ewes are yarded is a useful exercise to measure the nutrition of your ewes and a good guide as to how they are likely to respond at joining. 

An increase of 1 fat score unit will correspond to an increase in body weight of 7-8 kg, regardless of frame size. One extra fat score unit in Merino ewes at joining results in about 13 extra lambs born per 100 ewes joined.

Producers wishing to ensure high lamb-marking percentages should target a fat score 3 for their ewes at joining. 

Ewes joined at high static weights and at fat score 5, and who maintain this fat score throughout gestation, are likely to experience difficult births and pregnancy toxaemia.

Read more about ewe nutrition.

Ram preparation

• Rams should be checked prior to joining for general and reproductive health - carry out the 'four Ts' health check: teeth, testes, toes and tossle.
• Rams can benefit from a high-protein and energy diet in the eight weeks leading up to joining.
• Sperm development takes around seven weeks, so avoid any stress, activities or treatments during the eight weeks prior to joining.

Read more about breeding rams.

Advice when joining ewes in dry conditions

When faced with poor seasonal forecasts, if is important for producers plan ahead with feed. Joining ewes without planning for lambing in the following year will only lead to further ewe loss.

Lamb survival through to weaning may depend on managing for poor availability of grain due to lack of harvests and demand for seed.

Early weaning gives ewes the potential to regain body weight but also relies on this date in relation to the break in the season or drying-off of the season. If weaning has been early, ewes will have regained body reserves and achieved high static body weight before pasture deteriorates in quantity and quality over summer.