Review: Toilet training in pigs: Theory, methods and design.

Pigs naturally separate their elimination area from their lying area. However, in intensive farming systems, it is a challenge to structure the pens in a way that all pigs eliminate in the designated areas. The concept of a pig toilet has been proposed to increase animal welfare and reduce ammonia released in pig farming. A pig toilet is defined as a designated limited area within the pen where pigs voluntarily excrete and can be rewarded for depositing their urine and faeces. This review aims to assess, from a behavioural and design point of view, the feasibility and potential solutions of training pigs to use a toilet. An extensive literature review was conducted on pig elimination behaviour, learning abilities, and toilet training studies. In summary, the potential to train pigs to use a toilet with a reward seems promising. On the other hand, to apply the toilet in practice, automated toilet training of pigs in a group remains challenging. Potential risk factors that can hamper toilet training are related to the nature of pig elimination behaviour, the characteristics of the toilet, training procedures and current technical constraints. We conclude from this review that it is feasible to toilet train pigs using positive rewards depending on the training process and the design of the toilet; more research is needed to optimise toilet design and implement the toilet in practice.