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Bulletin No. 16 - Fall 2003
Parasitology- No Category
DAMM BI, PEDERSEN LJ, JESSEN LB, THAMSBORG SM, MEJER H, ERSBOLL AK.
The gradual weaning process in outdoor sows and piglets in relation to nematode infections.
Applied Animal Behaviour Science 82:101-120, 2003
In EU organic pig production it is required that the piglets are weaned no earlier than 6 weeks of age. During the lactation period, a gradual weaning process occurs. Outdoor and organic pig production differ markedly from semi-natural and indoor environments, where the gradual weaning process has been studied in detail. The differences include the sows' opportunity for foraging and the feed availability, and compared to indoor pigs also a greater incidence of gastro-intestinal parasitic infections, which may interfere with feed consumption and utilisation of nutrients. In order to describe the gradual weaning process in an outdoor environment and investigate the possible effects of gastro-intestinal nematode infections on the behaviour during the period relevant for organic pig production, we studied the behaviour of 16 sows and their litters kept in separate paddocks with farrowing huts on days 16, 23, 30 and 44 postpartum and their growth rate and feed consumption during the same period. Half the sows and half of each litter were experimentally infected with Ascaris suum, Oesophagostomum dentatum and Trichuris suis. A gradual weaning process took place. The frequency of nursings declined, the piglets were increasingly responsible for initiating nursings, they increasingly visited a piglet feed trough and ate more solid feed, as lactation progressed (all P < 0.001). The sow terminated 100% of the nursings and neither this nor the duration of the post-massage phase changed during the experimental period. Other behaviours usually considered important in the gradual weaning process were unexpectedly rare, i.e., piglets missing at milk let-down (0% of the litter), piglet massaging the udder between nursings (0.7% of scans), non-nutritive nursings (6.3% of nursings) and nursing in a standing position (one sow). There were only negligible effects of ;nematode infection on nursing behaviours, behaviours performed between nursings, body weight, weight gain and feed consumption in sows or piglets. The results indicate that infected sows did not have to restrict their allocation of resources to piglets further when infected than that which is part of the normal gradual weaning process. However, the infected sows spent more time in the huts (42% versus 29% of scans, P=0.02) perhaps to preserve energy, whereas their piglets probably did so (P=0.04) because they wanted to stay close to their mothers.
