The dynamic model of growth of an animal from conception through to maturity (Vetharaniam, 2001 A model of mammalian energetics and growth: model development. Agricultural Systems, 68, 55-68) is tested against data for sheep growth, to gauge its usefulness. The model is based on opposing forces of anabolism and katabolism, and does not include forcing functions for growth. The model gave good predictions of fetal and placental growth dynamics for sheep, including the differences between singleton and multiple offspring, as well as reproducing the post-natal growth patterns corresponding to rams with genetic merit similar to that of the fetuses. Although maintenance and fasting heat production are not explicit concepts in the model, the model was able to reproduce these through its mechanisms.