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 duri ng the first 2 months of lactation in two groups of six and five saddl e mares respectively made thin or fat before foaling, then fed ad lib. post partum. Milk yield did not significantly vary with body conditio n (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 reve rse was found for protein. The composition of milk fat was modified: m ilk 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 diffe rence in lipid mobilization, as shown by variations in non-esterified fatty acids.