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A study was conducted to describe the changes occurring in body composition of ostriches over a 285-day growth period. Fifty two birds were given a choice of four diets with different protein (180 and 120 g/kg feed) and energy (8.5 and 13.5 MJ ME/kg feed) levels, on the assumption that the birds would select from the four feeds according to their protein and energy requirements, and thereby grow close to their potential without being constrained by the quality of feed supplied to them. Birds were weighed at approximately 10-day intervals and randomly selected birds were slaughtered at 1, 54, 120, 162 and 285 days of age respectively. Proximate analyses were done on the complete empty carcasses and the components were expressed as a percentage of live weight at the different slaughter ages. The Gompertz growth curve was fitted to the live weights of the birds and to the weights of the individual chemical components. The change in body weight with age as the only independent variable can be considered as a good (R2 = 0.93) description of growth in ostriches. The growth parameters a, b and c were estimated as 119.4, 0.009 and 156.3
respectively. Body protein and moisture concentrations decreased as the birds aged, while the body ash concentration remained relatively constant and body fat concentration increased. Fitted Gompertz parameters for the different chemical components were, for fat; a = 33.6, b = 0.013 and c = 143.4 (R2 = 0.914), protein; a = 44.5, b = 0.015 and c = 113.9 (R2 = 0.961), ash; a = 10.3, b = 0.016 and c = 118.2 (R2 = 0.965), and moisture; a = 55.0, b = 0.014 and c = 116.9 (R2 = 0.965). Similar to other animals, fat was a late maturing tissue and protein a relatively early maturing tissue. These results are important in describing the growing
ostrich and this information can be used to model the nutrient requirements of these birds.
Keywords: Growth, development, feeding optimization, proportional changes, Gompertz growth curve