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Welfare Implications Reviewed of Large Litter Size in the Domestic Pig

15 May 2013

Two recently published papers - the result of collaborative projects by several leading European animal science institutions - review the biological and management factors associated with breeding for increased litter size in pigs and with implications for the welfare of both sows and their piglets.

Biological Factors

Increasing litter size has long been a goal of pig breeders and producers, and may have implications for pig (Sus scrofa domesticus) welfare. A paper1 in the journal, Animal Welfare, by Kenny Rutherford of the SRUC in Edinburgh and others reviews the scientific evidence on biological factors affecting sow and piglet welfare in relation to large litter size.

It is concluded that, in a number of ways, large litter size is a risk factor for decreased animal welfare in pig production. Increased litter size is associated with increased piglet mortality, which is likely to be associated with significant negative animal welfare impacts.

In surviving piglets, many of the causes of mortality can also occur in non-lethal forms that cause suffering. Intense teat competition may increase the likelihood that some piglets do not gain adequate access to milk, causing starvation in the short term and possibly long-term detriments to health.

Also, increased litter size leads to more piglets with low birth weight, which is associated with a variety of negative long-term effects.

Finally, increased production pressure placed on sows bearing large litters may produce health and welfare concerns for the sow.

However, possible biological approaches to mitigating health and welfare issues associated with large litters are being implemented. An important mitigation strategy is genetic selection encompassing traits that promote piglet survival, vitality and growth.

Sow nutrition and the minimisation of stress during gestation could also contribute to improving outcomes in terms of piglet welfare.

Awareness of the possible negative welfare consequences of large litter size in pigs should lead to further active measures being taken to mitigate the mentioned effects.

Management Factors

Certain management interventions are used when litter size routinely exceeds the ability of individual sows to successfully rear all the piglets (i.e. viable piglets outnumber functional teats). Such interventions include: tooth reduction; split suckling; cross-fostering; use of nurse sow systems and early weaning, including split weaning; and use of artificial rearing systems.

These practices raise welfare questions for both the piglets and sow and are described and discussed in a review2 by Emma Baxter of SRUC and others, also in Animal Welfare.

In addition, possible management approaches which might mitigate health and welfare issues associated with large litters are identified. These include early intervention to provide increased care for vulnerable neonates and improvements to farrowing accommodation to mitigate negative effects, particularly for nurse sows.

An important concept is that management at all stages of the reproductive cycle - not simply in the farrowing accommodation - can impact on piglet outcomes. For example, poor stock-handling at earlier stages of the reproductive cycle can create fearful animals with increased likelihood of showing poor maternal behaviour.

Benefits of good sow and litter management, including positive human-animal relationships, are discussed. Such practices apply to all production situations, not just those involving large litters. However, given that interventions for large litters involve increased handling of piglets and increased interaction with sows, there are likely to be even greater benefits for management of hyper-prolific herds.

Reference

1. Rutherford K.M.D., E.M. Baxter, R.B. D'Eath, S.P. Turner, G. Arnott, R. Roehe, B. Ask, P. Sandøe, V.A. Moustsen, F. Thorup, S.A. Edwards, P. Berg and A.B. Lawrence. 2013. The welfare implications of large litter size in the domestic pig I: Biological factors. Animal Welfare. 22:199-218. doi: 10.7120/09627286.22.2.199

2. Baxter E.M., K.M.D. Rutherford, R.B. D'Eath, G. Arnott, S.P. Turner, P. Sandøe, V.A. Moustsen, F. Thorup, S.A. Edwards and A.B. Lawrence. 2013. The welfare implications of large litter size in the domestic pig II: Management factors. Animal Welfare 2013, 22: 219-238. doi: 10.7120/09627286.22.2.219

Further Reading

You can view the full reports (fees payable) by clicking here.

May 2013

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