CALCIUM AND PHOSPHORUS-METABOLISM AND EGGSHELL FORMATION OF HENS FED DIFFERENT AMOUNTS OF CALCIUM

Twenty-seven 42-wk-old Single Comb White Leghorn hens housed in separate cages were fed either 2.5, 3.5, or 4.5% Ca diets, each providing .45% available P. Birds were allowed a 7-day adaption period followed by an 8-day collection period. Feed and water were available for ad libitum consumption with feed intake recorded daily. Eggs and excreta were collected daily for mineral analysis. Feed, Ca, and P intake of hens increased significantly (P < .05) on shell-forming (SF) days compared with days on which shell formation did not take place (NSF). Dietary Ca level had a significant (P < .05) effect on feed and Ca intake of hens. On SF days, hens retained more dietary Ca, both as a percentage and per gram Ca basis, compared with NSF days. As dietary Ca increased, the percentage Ca retained decreased (P < .05) and per gram Ca retained increased (P < .05). Dietary Ca had no effect (P > .05) on egg weight or egg production. Increasing dietary Ca significantly (P < .05) decreased shell deformation and increased (P < .05) shell weight and grams of shell Ca, although there was no significant (P > .05) effect on percentage shell Ca. Calcium retention increased linearly (P < .05) as Ca intake increased, and shell weight increased quadratically (P < .05). There was a diminishing response of shell weight to Ca intake at higher levels.