Parity Profile is Key to Prolificacy

Pig trend figures over time show that parities three to six are the most prolific.

Therefore, the more productive sows that are retained in these parities, the more likely a herd will deliver a good result.

Some units are now culling at five parities, due to the older sows’ association with reduced numbers born alive and rearing ability, as shown in the unit profile in Figure 1.

Figure 1. Piglets born and weaned fromsows of different parities
Note the decline is numbers weaned for higher-parity sows

And this is only part of the story. Reporting by Agrosoft Ltd showed conclusively that sows of more than seven parities were more likely to return to service, thereby accruing empty days and reducing the farrowing index.

So it is imperative that producers manage parity profile to maintain an optimum population spread, similar to that in Figure 2.

Figure 2. Manage parity profile to maintain an optimum population spread

The aim is to have at least 45 per cent of sows in parities three to five, with the optimum being 50 per cent.

This can only be realised by careful planning and management of replacement gilts and, most importantly, retaining them in the herd.

The profile in Figure 2 shows that, in general, only 9.4 per cent of served gilts have been lost by the time they reach their third parity.

This is excellent and means the herd is maintaining a high percentage of sows in parities three to five.

However, it is not uncommon to see much higher losses – around 30 per cent – of gilts being removed by the time they reach third parity.

This usually results in two possible scenarios:

• the herd has too few sows in the productive parities and a ‘long tail’ with older sows having to be retained to reach target service numbers, or
• the unit has a high annual replacement rate of 45 to 50 per cent, as they are replacing both young and older sows.

This is a costly situation because gilts usually need to be retained for three parities before they pay for themselves.

In both scenarios, there is only one outcome: a reduction in herd performance and increased cost of production

To manage the parity profile effectively, pig managers must plan ahead and introduce sufficient gilts into the isolation/gilt pool so that there are enough available gilts prepared for service at the right time.

Top Tips for the Autumn

Autumn abortions: Our modern sows’ ancestors were seasonal breeders and only produced one litter a year, farrowing in early spring.

So there is an in-built biological reason why the modern sow sometimes has problems with summer infertility and autumn abortions. Management factors to help reduce autumn abortions include:

Energy Level: When temperatures decline the sow’s energy requirement increases. It is important to adjust feed curves or diet specifications accordingly. If sows have to use their body reserves to maintain energy level, it can cause some susceptible sows to abort.

Light Level: Decreasing day-length is another factor contributing to autumn abortions.

To maintain a viable pregnancy, sows need be exposed to a minimum of 16 hours of light (200 lux intensity) and eight hours of darkness. Simple interventions can be made to improve lighting such as cleaning sky lights, walls and lamps, putting electric lights on timers and painting the roofs and walls white.

Ventilation: For accommodation with controlled ventilation systems, it is time to re-adjust the settings after the summer. Incorrect settings can result in disease outbreaks, respiratory problems, tail biting and filthy pens.

If unsure about the right ventilation settings to achieve optimal airflow, consult the manufacturer or an expert consultant for advice.

Looking after Boar Libido

Heat stress in outdoor sows and boars will have been a problem during the summer, with temperature highs of 31°C. This prolonged heat poses a risk to fertility and libido in boars.

Sperm production occurs at 2 to 4°C below body temperature. Poor quality semen affects conception and litter size which all has an impact on the bottom line.

The boar’s scrotum and pampiniform plexus help maintain the right temperature but the boar is at particularly high risk because one-third of the testicles are inside the boar.

While weather remains fairly warm and dry, it is important to monitor boar libido and activity.

Consider using AI for six to eight weeks after any high temperature periods or if boar activity drops off.

September 2010