| Popis: |
Various aspects of growth are covered in other chapters, but because it is such an important topic, it is discussed more directly here. The characteristic S-shaped growth curve of all biological systems, whether it be an increase in weight gain of a plant or animal or increase in number of yeast cells in a population (Brody 1945) is shown in Fig. 5.1. The term growth, as applied to animal production, is often considered to be synonymous with increase in body weight of the animal from conception to maturity. Brody (1945) has defined growth as “the constructive or assimilatory synthesis of one substance at the expense of another (nutrient) which undergoes dissimilation.” The energetic efficiency of growth as just defined is, therefore, the energy stored in the animal per unit of energy consumed. The pig is especially efficient in growth, in comparison with other farm animals. Detailed discussion of the energetic efficiency of growth in meat-producing animals has been provided by Webster (1980). The complex metabolic and endocrine aspects of tissue and animal growth are exciting areas of animal biology and have been reviewed by Trenkle and Marple (1983>) and in a symposium, Concepts of Animal Growth (American Society of Animal Science, 1988). |
