The pregnant mare would need either grass forage in a different pasture or hay. Supplemental feed alone would not provide the long fiber needed. In the case, the crowding of buffalo in a neighbor’s pasture is criticized. Overcrowding limits available forage and substantially increases the potential for parasite infection. Parasites can be picked up when animals eat the larvae of flatworms and roundworms living in their pasture feed. How do the larvae of these animal parasites get into the grass?