At first, the fertilized ovum divides mitotically with little or no growth in mass. However, as soon as it develops the means of assimilating energy, the growth of the embryo accelerates. At birth and weaning there may be a temporary deceleration of growth as an animal switches from one source of nutrients to another. Except for a slight acceleration at puberty, subsequent growth maintains a steady average velocity until the terminal deceleration that occurs as animals reach their mature size. Anabolism versus catabolism Anabolism is the building up of body components, while catabolism is their destruction.
All live animals show both anabolism and catabolism.
If anabolism exceeds catabolism, the animal is growing. If catabolism exceeds anabolism, the animal is wasting away. If anabolism equals catabolism, animal weight is constant. Protein turnover is the time between anabolism and catabolism of an individual protein. For meat animals, the half-lives of the important meat proteins are around several days in length, with muscle proteins being much faster than connective tissue proteins.