ABSTRACT
Although a general relationship exists between peak milk yield (or milk energy output) and maternal metabolic body size (body mass0.75),[5,6] there are large differences in peak production among species independent of metabolic body size. In terrestrial mammals, species with large litters, such as rats, dogs, and pigs, have peak milk energy outputs per maternal metabolic size that are two to three times those of ungulates with one young (Table 1). The peak energy outputs of most primates are even lower. The highest daily outputs of milk energy are found among seals. The hooded seal appears to be the mammalian champion: Its daily milk energy output is four times that of a pig, 11 times that of a horse, and 27 times that of a human, relative to metabolic size.
