The benefits of more informed sow culling

Culling a sow is one of the most important management decisions a producer can make. In making the decision, the first consideration should be whether the welfare of the sow is compromised. Should this be the case, then the sow should be hospitalized, destroyed or culled immediately.

However, if the sow’s welfare is not compromised, the second question should be whether there is an additional pregnant gilt that will farrow in the same batch. If not, the sow cannot be culled.

The financial impact of the time of culling.

Timing of culling 

On many farms, sows are culled at the point of weaning. Perhaps the decision is even made during lactation, but why?

There are three major times when culling should be considered:

• At the end of the breeding week
• At the first heat check
• At the pregnancy check

Keeping cull sows beyond the breeding week

Sows, as they age, need to be culled. Culling sows after breeding provides options for the farm – it does not stop the culling and replacement of old sows.

When we wean on a Thursday, the first day of the new batch should be Friday. Breed all possible sows (including culls) over the breeding week. Then review the number of females which have been mated. If the breeding target has been easily met, remove the cull sows the following Friday.

In addition, retaining the sow for a week, allows the udder to regress and even possibly some lameness/stiffness issues have been corrected.

Sows kept until pregnancy checking

If we retain the sow until pregnancy check, the concept is to ensure that sufficient sows are pregnant before any culling takes place. If sufficient sows are pregnant, do not spend time pregnancy checking the sow marked for culling. The duly culled pregnant sow will not be recognized at slaughter, as 28 day foetuses are extremely small. Culling at this stage brings the additional benefits of recovery from weaning and lactation with the possibility of additional weight recovery.

A possible secondary advantage of these pregnant animals is that through pharmacological abortion, they may be used to fill holes in the breeding program.

Sows culled pre-farrowing

It is not contemplated that extra sows are kept to the point of farrowing. It is assumed that the number of pregnant sows that enters the farrowing pool will equal 110% of available farrowing places – thus for a 10 sow batch farm – 11 pregnant sows will enter the pool.

If you retain all bred sows in excess of 110% to the point of farrowing, welfare problems will arise associated with the overstocking in the farrowing, nursery, grower and finishing areas.

Some sows still need to be culled

Some sows still need to be culled, however, and these include:

• Any sow or gilt which has a welfare problem
• Return sows - even sows or gilts that return once should be culled if possible
• Sows with behavioural issues - sows that kill piglets or low numbers weaned

Which sows should not be automatically culled?

• Sows of a particular age
• Sows with one litter of low numbers
• Sows that look at you funny

Making decisions about replacing a sow

If a culling programme is to change, when should decisions be made to cull?

Farrowing . When the batch fails to fill all the farrowing places, you must immediately add gilts to the system.

The farm’s team already knows that there is going to be a need for extra gilts in five weeks’ time (four week weaning).

If it is impossible to hit the next batch breeding target, there is no excuse to again fail to reach the batch breeding target in 20 weeks time, when the batch farrows, weans and then breeds again. If a mistake occurs in this batch, accept it. But ensure that it does not happen again.

Breeding . At the point of breeding, if the breeding target is missed, future gilts for the next time this batch is going to be bred need to be prepared. They will be around 10 weeks of age.

Pregnancy diagnosis . At the time of pregnancy diagnosis, the likely number of sows that will farrow in this batch is known. The future gilts required to mate within this batch next time round, are now 15 weeks old.

10-11 weeks of gestation . All sows around weeks 10-11 of pregnancy should be carefully examined by the farm manager. Any sow that is deemed to be suboptimal should be marked for culling. Selected future gilts need to be added to the pool so that they will be in second, third or fourth oestrus post boar exposure when this batch is being bred again.

Let us assume that the gilts enter the breeding pool at around 100kg, are introduced to a boar, cycle within five days and then cycle twice before being bred (mated on her third heat into the breeding pool), this is seven weeks post introduction into the breeding pool. Reviewing the future breeding batch at 10-11 weeks of pregnancy gives the farm time to ensure breeding targets and met.

What should be looked for at 10-11 weeks of gestation?

1. Ensure all sow to be retained sows are pregnant – visual assessment.

2. Ensure that all future sows are sound on all their feet.

3. Ensure that all future sows have no visual gross abnormalities to their udders.

4. Review the sow’s performance – age, # weaned, # total born (not born alive), returns.

If the culling programme is changed, how many sows should farrow?

The obvious minimum answer is the number of batch farrowing places, but note that the term is minimal. To achieve this, there should always be sufficient pregnant sows post six weeks of gestation to fill 110% of farrowing places, sows to farrow – per batch.

But if the example farm has 10 farrowing places: where is there room for 11 sows to farrow?

The farm can fill 110% farrowing place capacity adopting the following concept:

Several batches a year will present with 11 sows pregnant in week 16 of gestation. Load the farrowing places with 10 pregnant sows as normal, around 110 days of gestation. Leave the sow mated last in the breeding batch in the gestation area. When about the third sow farrows (not a first or second parity sow) allow the piglets to suckle colostrum from their mother for about 12 hours, and then wean. Distribute the piglets to the previously two farrowed sows. The weaned sow is moved into the next breeding batch.

The sow retained in the gestation area is moved into the empty farrowing place. The piglets are used to even up litters, especially to gilts and low litter sows. With tight breeding schedules, farrowing should also be tight, making this manipulation fairly easy. It is obviously vital to ensure that the sow which stays in the gestation area does not farrow there. The targets should be 12 weaned per batch farrowing place.

This method boosts the farrowing output, which is the purpose anyway, and maintains all-in/all-out or induce more variation in weaning age.