title: Calcium requirements of the modern broiler chicken as influenced by dietary protein and age.
abstract: Two experiments were conducted to examine the calcium requirements of broiler chickens fed corn-soybean meal diets. Experiment 1 used a 6 x 2 x 2 factorial arrangement and was conducted with broilers in floor pens during the grower phase (19 to 42 d). Diets were mixed with 6 levels of dietary Ca (0.325, 0.4, 0.475, 0.55, 0.625, and 0.9%) and 17 or 23% CP and fed to males and females separately. Experiment 2 was a 6 x 2 factorial design conducted using Petersime battery brooders during the starter phase (0 to 16 d). The same 6 levels of dietary Ca used in experiment 1 were fed separately to each sex, but only at the 23% level of CP. The diets used in both experiments were formulated to contain 0.45% nonphytin phosphorus. In experiment 1, grower chickens did not demonstrate significant body weight gain (BWG) or feed conversion ratio (FCR) response (g of feed per g of gain) to the different levels of Ca at either level of protein. The percentage tibia ash did not respond to increasing Ca levels beyond 0.625% Ca at either protein level. In experiment 2, BWG increased linearly up to 0.55 and 0.625% dietary Ca for males and females, respectively. Feed conversion ratio decreased linearly with increasing dietary Ca up to 0.625% Ca, and tibia ash was highest at 0.9% Ca for both sexes. These results suggest that the current NRC Ca requirements for the broiler starter (1.0%) are sufficient for maximum bone ash, but that Ca requirements for grower birds (0.9%) may be excessive for optimum BWG, FCR, and tibia ash.
authors.affiliation: Department of Poultry Science, The University of Georgia, Athens, Georgia 30602-2772, USA. jdriver@jax.org
authors.forename: J P
authors.initials: JP
authors.lastname: Driver
authors.forename: G M
authors.initials: GM
authors.lastname: Pesti
authors.forename: R I
authors.initials: RI
authors.lastname: Bakalli
authors.forename: H M
authors.initials: HM
authors.lastname: Edwards
mesh_terms: D000375:Aging / Q000378:metabolism*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D002645:Chickens / Q000235:genetics / Q000254:growth & development*; D004044:Dietary Proteins / Q000378:metabolism*; D005260:Female; D008297:Male; D012044:Regression Analysis
chemical_list: D004044:Dietary Proteins; D002118:Calcium