Dietary Calcium Availability and Reproduction in Birds

摘要: Reproduction is energetically costly. Egg formation in birds requires 37–55% of basal metabolism for small passerines and 160–216% ducks the Southern Brown Kiwi (Apteryx australis) (Walsberg 1983). The production eggs an adequate supply water, macronutrients (carbohydrate, protein, fat), micronutrients (essential fatty acids, amino vitamins, ions). Of this latter group nutrients, calcium probably most limiting micronutrient required by laying bird (Burley Vadehra 1989); 98% dry mass eggshell consists calcite, a crystalline form carbonate (CaCO3) (Romanoff Romanoff 1949). encases all nutrients embryonic development survival during incubation period, preventing developing chick from being crushed incubating adult. shell also protects embryo dehydration, prevents entry pathogens external environment, allows gaseous exchange. It acts as source skeletal embryo. withdrawal skeleton results “natural thinning” ∼6% (e.g., Balkan et al. 2006) to 21% Booth Seymour 1987) absorbs incubation. After egg production, requirements adult many species must remain elevated chick-rearing, when feed calcium-rich foods their young (see Table 3 Graveland 1996a) continued mineralization skeletons (Starck 1998).