Live-weight growth from embryo to adult in domesticated mammals

The inter-species relationship between mature body weight and time taken to mature in body weight was studied empirically in nine domestic species with data ranging from early embryonic to late postnatal growth. When examined in terms of genetic size scaling, the results showed that metabolic age provided a readily useable comparative age scale which would allow results obtained from one species to advance the study of growth and nutrition in other species. A standardized growth curve was therefore calculated for each species in terms of degree of maturity in body weight and metabolic age. The two standardized regression curves gave mean growth curves that estimated expected degree of maturity at a given metabolic age and expected metabolic age at a given degree of maturity. The two mean curves scarcely differed. Deviations of each species from these mean curves were analysed. There were significant standardized differences between species in earliness of maturing. Rabbits were estimated to mature in 30% less time than expected for their size, a deviation which (if repeatable) could be of great potential importance to animal production.