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Piglet Fostering — Art Or Science?

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Sometimes where litter size is very large it is necessary to foster piglets soon after birth.

Bernie Peet is president of Pork Chain Consulting Ltd. of Lacombe, Alberta, and editor of Western Hog Journal.

Fostering of piglets from one sow to another soon after birth is a technique that has been used for many years, well before today’s highly prolific sows made it an essential practice. Fostering has two main objectives – to adjust the number of piglets suckling on a sow to match the number of functional teats and to even up the size of piglets in a litter.

Stockpersons often have their own ideas about how and when fostering is done, but what does the science tell us?

First, a little background on some of the factors that impact on the technique of fostering and piglet survival. Birth weight has by far the largest impact on piglet survival. The biggest pigs are born first, which means they are less likely to suffer from anoxia – oxygen starvation – during the birth process, and these pigs suckle the front part of the udder where the milk supply is greater. Conversely, light-weight pigs are born later and have a higher chance of suffering from anoxia, making them lethargic and slow to reach the udder. These smaller pigs compete less successfully for a teat and usually suckle the hind teats which produce less milk.

In addition, they achieve fewer sucklings and are less vigorous in their stimulation of the udder, leading to reduced milk let-down. Worst of all, the delay in suckling means that they are likely to ingest less colostrum, reducing the passive immunity acquired from the sow.

Because colostrum intake is so crucial, fostering techniques must be focused on ensuring piglets ingest enough to provide the immunity they need to fight off disease challenges. Although colostrum may be available to piglets for 24-36 hours after birth, the level of antibodies drops quickly after farrowing and by 12 hours after the birth of the first piglet are only 35 per cent of the level present at the start of farrowing (see table). This means it is extremely important that piglets are able to consume the colostrum they require within a maximum of six hours after birth. This has significant implications for how and when fostering is carried out. Various management practices, such as split suckling, syringe feeding and assisting small piglets to suckle can be used to ensure adequate colostrum intake.

As a general rule piglets should suckle colostrum from their own sow. However, sometimes where litter size is very large it is necessary to foster piglets soon after birth. If this is done, the foster sow should have farrowed within the last few hours and have a good supply of colostrum.

While some fostering may have to take place as part of colostrum management, where possible it should be delayed for five to six hours but then be done promptly.


Some general recommendations on how this should be done are:

Assess the rearing ability of the sow by reference to her lifetime history record and through a visual check of functional teat numbers, paying special attention to nonfunctional glands and blind teats. Note the sow’s rearing ability on the farrowing card.

Plan all moves carefully before fostering, taking account of the sow’s rearing ability and number and size of piglets in the litter.

Minimize the amount of piglet movement between sows. If piglets are suckling successfully and not subject to excessive competition for a teat, do not move them.

Always move the largest piglets as they can cope with the stress of movement better.

Over the first 48 hours after farrowing, closely observe suckling behaviour to identify piglets which are not receiving sufficient milk from the sow and foster these piglets to another sow.


One other aspect of fostering is whether it is advantageous to group the smallest piglets on one sow. The theory is that by reducing competition from large piglets, they will have better access to a teat and consequently their survival chances will be higher.

However, some research suggests this may not be the case. A trial carried out at the University of Alberta in the late 1990s showed that splitting piglets into litters of heavyweight pigs or small pigs had no effect on survival compared with intact litters. The primary factors influencing survival were birth weight and the individual sow.

Despite these findings, in practice many stockpersons do group up small piglets on one sow and are able to increase their survival rate. First, they select a foster mother from second-or third-parity sows, which has easily accessible teats, a good milk supply and is quiet. Once fostering is completed, special measure are then taken to improve survival, such as leaving additional heat lamps in place for a few days and supplying milk substitute in trays. When carried out diligently, experience suggests this is effective in saving more piglets.

So, is fostering a science or an art? Knowledge of the science, especially relating to piglet immunity and colostrum intake is essential to understand the importance of timing. In addition, an understanding of piglet social behaviour during the port-natal and suckling period is helpful. But the most successful stockpersons are those that can quickly distinguish between piglets that have a good milk supply and those that don’t so that fostering can be timely and effective. That is certainly a skill, if not an art.

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