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The effects of motherless rearing in artificial rearing systems on the behaviour and development of surplus piglets

In the past, the focus in pig farming was on producing as many piglets per litter as possible. This resulted in litters that increasingly contained too many piglets, and these surplus piglets were increasingly reared using artificial systems. When this equipment was introduced, it was not known how the piglets would respond to being brought up without a mother. Roland Weber and his team have investigated the resulting research aspects.

Interview with Roland Weber, project manager at the Centre for Appropriate Management of Ruminants and Swine, Agroscope Tänikon (ZTHT), FSVO

 

Why was it necessary to study the effects of rearing piglets using artificial rearing systems?

For the past twenty years or so, the production of increasingly large litters has been a major goal in pig breeding. The producer’s profit is directly related to the number of piglets a sow is able to rear successfully. Each piglet must have a teat to suckle because the sow always suckles all her piglets at the same time. If the litter contains more piglets than the sow has teats, the weaker piglets can’t suckle and they starve. Breeders were so successful that over-large litters became increasingly common. A way to stop surplus piglets from starving had to be found, and stall construction companies started to supply artificial rearing systems. These are systems that allow piglets to be reared without a mother. They provide the piglets with artificial sow’s milk.

 

When did it become clear that there were problems, and what led to the research project being set up?

In Switzerland, mass-produced animal housing systems require official approval. Approval is only granted if the systems comply with the requirements for animal-friendly husbandry. The ZTHT operates this approval procedure on behalf of the FSVO. About five years ago, two artificial piglet rearing systems were submitted for approval. Our investigations quickly showed that almost nothing was known about how piglets react to being reared in a system of this type. In order to grant approval, we first did some research to see whether rearing piglets in an artificial system is compatible with the principles of animal-friendly husbandry. The first project looked at the effects of motherless rearing on the piglets’ behaviour. A second project then focused on finding ways of preventing the disturbed behaviour identified in piglets.

“Rescue Deck” artificial piglet rearing system with a lying area behind the strip curtain. The three milk cups are shown in the foreground. (picture provided by M. Lörtscher, FSVO)

 

Is there no way of rearing surplus piglets other than artificially?

If another sow in the stall produces a small litter at the same time, the surplus piglets can be transferred to her. This approach can be used systematically in large-scale operations. In the herd sizes commonly found in Switzerland, however, there are often no or too few sows with small litters in the same farrowing group.

Another possibility would be to provide additional feeding in the farrowing pen, but this is not easy to do in the farrowing pens that are mandatory in Switzerland, where the sows can move around freely, and it involves a lot of work. The main problem here is that the artificial sow’s milk is also drunk by piglets that don’t need it. As this product is very expensive it is probably not worth providing additional milk for the whole group, in contrast to the situation in calf rearing, where this is worthwhile.

 

What does early separation mean for the piglets reared without a mother?

Our research has shown that artificially reared piglets develop abnormal behaviour. One striking aspect was “belly nosing”, when piglets rub their snouts up and down against the bellies of pen mates. This is precisely what the piglet does to the sow’s teat when it suckles naturally. These piglets also play less and are more aggressive. And they rest less.

 

Were there differences between the two systems that were tested?

The systems were not compared directly. One was tested at the Agroscope research facility in Tänikon, the other on three working farms which had been granted a temporary license for the purpose. The behavioural disturbances were only seen in piglets reared artificially, and occurred with about the same frequency and for the same duration in both systems. Belly nosing was not observed in piglets reared in parallel under conventional conditions with the mother sow.

 

What consequences did the research findings have?

These artificial rearing systems can’t really be approved because they lead to intolerable behavioural disturbances. But this creates a dilemma. If the artificial rearing systems are not approved, the surplus piglets have to be killed, or they starve. In the interests of animal welfare we need to accept the artificial rearing systems even though they are not ideal for the piglets. We have launched a follow-up project to find ways of preventing, or at least mitigating, the behavioural problems.

 

What is the focus of the follow-up project?

The aim is to find objects with a high potential for reducing belly nosing in artificially reared piglets. In the first part of the project, the artificially reared piglets were offered pairs of different rubber teats to replace the sow’s teats and different cushion materials as replacement udders against which they could perform the massaging action. The researchers noted which of the available objects were preferred by the piglets. A total of three teats and three massage objects were tested.

In the second part of the project, an additional combination of suckling and massage object will be added to these objects. These will undergo several rounds of testing. There will also be a control group in which the piglets will be provided with no objects at all.

 

Are results already available, and if so, are they positive?

Only the first part of the project has been completed so far. It emerged that the piglets spent about the same amount of time with all the suckling and massage objects that they were given and that belly nosing happened with all the objects. We won’t know whether belly nosing can be reduced until the second part of the project is finished.

 

What is likely to happen now? Will litter sizes continue to grow, meaning that more and more piglets are reared artificially and develop behavioural abnormalities?

Nowadays more attention is paid in Switzerland to the rearing rate, i.e. the number of piglets per litter that are weaned. Only piglets reared by the sows are included in the figure. This will lead to a levelling out of the number of piglets per litter, or at least the number will increase more slowly. This approach to breeding should also mean fewer surplus piglets. In other countries, however, farmers are still deliberately trying to increase their litter sizes, so the problem is going to be around for some time to come.

 

Are these artificial rearing systems likely to become common?

It’s unlikely that every breeding operation will have an artificial rearing system because they are expensive and require good management, and that in turn involves more work. A lot of pig producers will go for other solutions, e.g. more systematic redistribution of piglets within a farrowing group.

“Nursery” piglet rearing system with lying area in a box filled with deep litter (right). The milk feeding system is shown in the middle. (picture provided by M. Lörtscher, FSVO)