Size, or its commonly used proxy live weight, is a necessary input when calculating the energy requirements of an animal. It is also a major factor in determining the intake capacity of an animal. The sole use of live weight as a determinant of size incorporates the implicit assumption that body fat and body protein mass are equivalent for the purposes of calculating energy requirements and intake capacity. Recent evidence indicates that this is not so in either case (Birnie et al., 2000; Friggens et al., 1998). The use of live weight may be acceptable where it can be reasonably assumed that there is a stable relationship between body fat and protein. However, when making breed or parity comparisons there is no reason to assume a stable relationship between body fat and protein. Meaningful comparisons can be made if live weights can be adjusted for differences in body fat content. In the applied context this means adjusting to a standard body condition score. This study provided the opportunity to examine the relationships between condition score and live weight in three breeds across three parities.