Changes in body weight and condition of gestating mares

Changes in body weight, condition scores, and rump fat thickness were observed in 12 mares during an entire gestation period. Mares had ad libitum access to forage (alfalfa hay or haylage) during the study. Total weight gain during gestation averaged 16% of the mares' initial body weight. The majority of weight gain occurred in the second, rather than third trimester of gestation. Only 30% of the total weight gain occurred in the third trimester of gestation. Estimates of body stores (condition score and rump fat thickness) increased during the second trimester of gestation as well. These observations suggest that the effects of pregnancy on the nutritional requirements of mares may not be confined to the last trimester of gestation.