With genetic improvements, sows can farrow bigger litters. So it is a common feature of modern pig farming that sows produce more piglets than they have teats available. The number of small piglets per litter has also increased. As a consequence, as many as 12% to 15% of piglets born alive die before they are weaned (Vande Pol et al., 2021). Pig farmers are now resorting to different managing techniques in the farrowing pen to reduce pre-weaning mortality. Chief among these is cross-fostering.