Get Out Of My Space! Pasture Size And Equine Aggression by Paulick Report Staff|09.14.202309.11.2023|7:55am2:59pm Though turnout has long been known to make a healthier horse, a new study from The Ohio State University suggests that the space available to the horse while he is outside is also important. Scientists at the school's Agricultural Technical Institute determined that a minimum of about one-tenth of an acre per horse is necessary to minimize aggression and reduce stress. Prompted by students in Dr. Jessica Suagee-Bedore's facility management class, the study used 12 healthy horses that were familiar with each other. The students first determined each horse's flight zone by allowing each horse to eat, then walking a second horse toward the eating horse until he showed signs of aggression like pinning his ears or turning his hindquarters toward the approaching horse. The study team then measured the distance between the horses. On average, each horse had a flight zone of about 33 feet. That figure was then used to calculate the total amount of space a horse would need in any direction to avoid contact with another horse: the result was 3,681 square feet. The second phase of the study kept four horses (two geldings and two mares) in different-sized pens for one hour. One pen offered 3,681 square feet per horse; one offered 2,831 square feet per horse; and the last gave each horse 1,981 square feet per horse. The scientists drew blood before turnout in the pens and at 15 and 60 minutes after turnout. The horses were observed for signs of stress and aggressive behavior like kicking or chasing. When not in the pens, the horses were kept in individual stalls. Horses kept in the larger pens had lower levels of blood cortisol 15 and 60 minutes after turnout. The horses in the smaller pens did not demonstrate decreased cortisol levels, and they displayed aggressive behaviors more often. The study team said that more research is needed into blood cortisol levels over a longer period of time, and to see how horses react in the different-sized pens when food is involved. Suagee-Bedore noted that the study focused only on the amount of space needed per horse to reduce stress, not to support grazing. The minimum acreage per horse needed to support nutritional intake and pasture growth is 2 acres per horse. Read more at EQUUS magazine.