title: Sigmoid growth analyses of wood ducks: the effects of sex, dietary protein and cadmium on parameters of the Richards model.
abstract: Growth analyses were conducted for 194 captive-reared wood ducks, using a reparameterized Richards process error model which provided estimates of: asymptotic size (W infinity); an approximation of the amount of time required to complete the growing period (T); and the Richards shape parameter (m). Multivariate analysis of variance indicated that growth was affected by sex and the level of cadmium in the diet on which the birds were reared (0-100 ppm). Crude protein in the diet (high = 30%; low = 18%) did not affect growth. Univariate analyses indicated that the growth of the sexes differed only with respect to W infinity, with males growing to larger body weights than females. Cadmium, however, altered both T and m, with longer times being required to complete growth in both controls which received no cadmium, and at higher levels of cadmium intake. Intermediate treatment levels completed growth in the shortest periods of time. Increasing cadmium intake altered the shape of the growth curve by progressively delaying the time at which maximum growth rate occurred.
mesh_terms: D000375:Aging; D000818:Animals; D000835:Animals, Wild; D001835:Body Weight / Q000187:drug effects; D002104:Cadmium / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D004372:Ducks / Q000254:growth & development*; D005260:Female; D008297:Male; D008433:Mathematics; D008954:Models, Biological; D012737:Sex Factors
chemical_list: D004044:Dietary Proteins; D002104:Cadmium