Yield and composition of milk from lactating mares: effect of body condition at foaling

The yield and composition of milk from nursing mares were studied during the first 2 months of lactation in two groups of six and five saddle mares respectively made thin or fat before foaling, then fed ad lib. post partum. Milk yield did not significantly vary with body condition (16.5 and 15.4 kg/d for fat and thin mares respectively). Milk from fat mares had a higher fat content than milk from thin mares; the reverse was found for protein. The composition of milk fat was modified: milk of fat mares was poorer in short- and medium-chain fatty acids (C8-C14). Milk fat output was affected by body condition: 252 and 187 g/d for fat and thin mares respectively. This can be explained by a difference in lipid mobilization, as shown by variations in non-esterified fatty acids.