Human–animal breastfeeding has been practiced in many different cultures in many time periods. The practice of breastfeeding or suckling between humans and other species has gone in both directions: human females sometimes breastfeed young animals, and animals are used to suckle babies and children. Animals were used as substitute wet nurses for infants, particularly after the rise of syphilis increased the health risks of wet nursing. Goats and donkeys were widely used to feed abandoned babies in foundling hospitals in 18th- and 19th-century Europe. Breastfeeding animals has also been practised, whether for health reasons – such as to toughen the nipples and improve the flow of milk – or for religious and cultural purposes. A wide variety of animals have been used for this purpose, includ