Timing of service in sows

Inseminating at the right time is essential to achieve the best farrowing rates and litter sizes. Use this information to ensure successful insemination and improved reproductive performance.

Back to Breeding performance in pigs

Why is timing of service so important?

Insemination must occur some hours prior to ovulation. This normally happens two-thirds of the way through oestrus (e.g. 36–44 hours after the onset of oestrus).

The 'correct' time to inseminate varies between farms and individual sows. It is important to adapt the insemination routine to individual farm characteristics.

Understand the process

There are a number of things you can do to get a better understanding of what works for your farm.

  • Sign up for specialised training in pig breeding and artificial insemination (AI) 
  • Familiarise yourself with the oestrus cycle in pigs to understand what happens, when, and what the signs are
  • Time your actions to fit with the breeding cycle 
  • Keep records – read more on Pig breeding and record keeping
  • Review recorded information regularly to determine any trends for your farm or for individual females, e.g. Is your herd generally a 2- or 3-day standing heat herd?
  • Tailor the insemination routine accordingly

Management guidelines

Identifying the start of standing heat accurately is the single most important thing to get right when scheduling the best time to inseminate.

Being too early or late could result in poorer litter sizes and lower farrowing rates.

If possible, undertake heat detection twice a day. This allows more accurate heat detection and timing of insemination.

Female pigs in standing heat may display a variety of signals, however the most important is standing to back pressure.

Boar stimulation

You should also make effective use of the boar to help stimulate and identify standing heat in breeding females.

The following video offers guidance on boar contact as part of an outdoor breeding environment.

Browse our other tutorial videos on YouTube


It is important to inseminate at least twice.

Acceptable fertilisation results are normally achieved by inseminating 24 hours before ovulation, however, it is impossible to know exactly when ovulation will occur, or to inseminate every female in their optimum period.

Carrying out multiple inseminations over the standing heat period will maximise success.

Aim for two inseminations during standing heat:

  • Sows – consider serving three times, where appropriate or under advice, no more than 24 hours apart
  • Gilts/returns/older sows – consider serving three times (e.g. AM – PM – AM)
  • Adapt the service routine to individual farm circumstances
  • Never inseminate a sow or gilt that is not showing a strong standing heat

What makes heat timings vary?

Most sows weaned on the same day will be reasonably well synchronised, but it is common to find sows coming into heat at different times after weaning.

Seasonal effects also mean that the timing of standing heat can differ by about 12 hours between good and poor breeding times.

It is important to adjust the timing of service to help maintain breeding performance.

Early sows

  • Short weaning to oestrus intervals (four days or less) are associated with longer oestrous periods (three days) and later ovulation
  • Adjust timings for insemination accordingly

Late sows

  • Long weaning to oestrus intervals (six days or more) are associated with shorter oestrus periods (two days) and earlier ovulation
  • Adjust timings for insemination accordingly

Seasonal variation

  • Oestrus tends to occur earlier from January to May than in the autumn
  • Oestrus tends to occur later from September to January than in the spring
  • Adjust timings for insemination accordingly

Useful links