title: Re-evaluation of calcium and phosphorus requirements in aged laying hens.
abstract: 1. A series of 5 trials was conducted with 401- to 650-d-old Lohmann, Yafa (local breed with brown eggshells) and Yarkon (local breed with white eggshells) hens fed for 56 to 84 d with diets containing 25 to 50 g/kg calcium (Ca) and 4.5 to 7.6 g/kg phosphorus (P). 2. Increasing dietary Ca from 24-25 to 36-40 g/kg improved egg production, shell weight (SW) and shell thickness (ST), and decreased mortality. 3. Increasing dietary Ca to 48 to 50 g/kg did not affect egg production but increased SW and/or ST. In one out of the 4 trials, this effect was not significant, most likely because of the high shell quality of the eggs from the Yafa hens used for this trial. 4. Dietary P content of 4.5 g/kg (1.0 g/kg added inorganic P) appears to be sufficient for maintaining egg production and shell quality in aged laying hen given 36 to 40 g/kg Ca. 5. Increasing dietary Ca above 40 g/kg may require a higher dietary P content.
authors.affiliation: Institute of Animal Science, Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel. ariebar@agri.gov.il
authors.forename: A
authors.initials: A
authors.lastname: Bar
authors.forename: V
authors.initials: V
authors.lastname: Razaphkovsky
authors.forename: E
authors.initials: E
authors.lastname: Vax
mesh_terms: D000375:Aging / Q000378:metabolism / Q000502:physiology*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002645:Chickens / Q000378:metabolism / Q000502:physiology*; D004528:Egg Shell / Q000378:metabolism; D004531:Eggs; D005260:Female; D009751:Nutritional Requirements; D010058:Oviposition / Q000187:drug effects / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism; D016226:Phosphorus, Dietary / Q000008:administration & dosage*
chemical_list: D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D010758:Phosphorus; D002118:Calcium