A note on precise tracking of suckling position by piglets

Piglets establish a relatively stable teat order after the first week of lactation, when each piglet chooses a preferred teat or teat pair where they tend to suckle permanently. The mechanism underlying the choice that leads each piglet to the same suckling position is still not clarified. In the present case study, piglets with different preferred suckling positions (anterior, posterior) were transferred to a foster sow after completion of the regular 4 weeks of lactation by their biological mother. For both sows, which were identical based on parity, litter size and farrowing date, we examined the suckling positions of the experimental piglets. Piglets occupied exactly the same suckling positions on both sows. Thus, piglets precisely track positions on the mammary complex of a sows udder even when previously learned discriminable stimuli have been changed, such as odours, tastes, morphologies (of sows udder or the sow itself), vocalizations, and neighbouring littermates. Our observation indicates that the spatial configuration of the mammary complex, which is determined by two parallel rows of teats arranged in pairs, can hypothetically be proposed as an important cue for piglet suckling orientation. Therefore, additional attention should be given to the exact spatial position of piglets (and vacant positions) on the mammary complex of biological and foster mothers in order to reduce stress from cross-fostering, which is standard practice in contemporary piglet production