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Cross-fostering Piglets on Commercial Sow Farms

Livestock Update, April 2001

Allen Harper, Extension Animal Scientist-Swine, Tidewater AREC

Fostering piglets from one sow to another within a farrowing group has been an established swine husbandry practice for many years. The purpose is simple, to reduce within-litter weight variation among piglets and to more evenly match the number of piglets with the sow's ability to nurse them. For example a first litter gilt may give birth to a large litter but, due to limited number of teats and milk production capacity, the gilt and her birth litter may perform better if a some of her pigs were fostered to a sow or sows with adequate teats and milk production.

A lot of what we know about cross-fostering piglets comes simply from the observations of experienced producers and farrowing barn managers. Interestingly, there has also been a substantial amount of practical research conducted on the behavior of suckling piglets and how cross-fostering can impact the sow and her litter. We know from research, for example, that piglets within a litter establish "teat fidelity" within 2 days after birth and each piglet within the litter will have a strong tendency to nurse the same teat throughout lactation. It is believed that the development of teat fidelity helps to prevent fighting and confusion among piglets during the 20 or more nursing periods that occur in each day throughout lactation.

With the increased use of segregated early weaning programs that place emphasis on weaning large numbers of heavy, uniform weight pigs at very young ages, there appears to be more frequent use of cross-fostering throughout the nursing period. Done properly, cross-fostering can be beneficial to sow and piglet performance. However, if done improperly or excessively, cross-fostering can have negative consequences. Swine researchers S. Robert from Quebec Province, Canada and G. P. Martineau from Toulouse, France reported on a study they conducted to assess the consequences of multiple cross-fostering of piglets throughout an 18 day nursing period (J. of Animal Science 79:88-93 [January 2001]). Their study teaches an important lesson about repeated cross-fostering and how it can affect both sows and litters.

In the study, litters produced from sows in farrowing crates were standardized within 26 hours of birth at 9 to 11 piglets per litter. There were 27 litters total, 13 litters designated as un-fostered controls and 14 litters further divided into 7 sow and litter pairs to be involved in cross-fostering treatments. On days 1, 4, 7, 10, 13, and 16 of lactation all piglets in the study were individually weighed within a 5-gram accuracy. After each weighing, three heavier weight pigs from the lightest litter in each sow and litter pair group were cross-fostered with three of the lighter weight pigs from the heaviest litter in the sow and litter pair. The researchers then carefully observed and recorded the behavior of all piglets in the study for 2 hours immediately after weighing and cross-fostering. Identifying marks were placed on the piglets to indicate if they were "resident" or "adopted" pigs in a cross-fostered litter. Pigs in the un-fostered litters were called "controls."

Some important and statistically significant observations in the study were as follows.

In this study repeated cross-fostering of piglets after an initial cross-fostering act at day 1 of age had measurable negative impacts on piglets and sows. For piglets these negative impacts included negative behavior such as increased fighting resulting in more face and body lacerations, more vocalizations indicating distressed piglets and less effective nursing time for cross-fostered litters. Repeated cross-fostering translated into poorer growth during lactation for adopted piglets and, to a lesser extent, for resident piglets within cross-fostered litters. Negative effects for sows included more aggressive acts toward piglets, less time lying on her side to expose the udder and a greater frequency of nonproductive nursing periods.

Even on large swine breeding farms that practice early weaning systems, it appears that traditional rules of cross-fostering still apply. These include ensuring that piglets receive colostrum rich first milk from their birth sows before transferring. This may require leaving piglets with their birth sow for 4 to 6 hours before transferring. And transfer of piglets should occur before they are 24 to 48 hours old, preferably to a sow that has also recently given birth so that teat fidelity among piglets is not firmly established. Once transferred it is desirable for resident and adopted piglets within the litter to establish teat fidelity. And preferably the newly established litter would be kept intact without repeated cross-fostering until weaning time.

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