title: Effects of Dietary Calcium Levels on Productive Performance, Eggshell Quality and Overall Calcium Status in Aged Laying Hens.
abstract: This study was conducted to investigate the effects of diets with varying levels of calcium on egg production, shell quality and overall calcium status in aged laying hens. A total of five hundred 70-wk-old Hy-Line Brown layers were divided five groups and fed one of the five experimental diets with 3.5%, 3.8%, 4.1%, 4.4%, or 4.7% Ca, for 10 weeks. There were no significant differences in feed intake, egg production and egg weight among groups. The cracked eggs were linearly reduced as dietary Ca levels increased to 4.7% (p<0.01). A significant linear improvement for eggshell strength and thickness were determined with increasing dietary Ca levels (p<0.01). The contents of serum Ca and phosphorus were not affected by dietary Ca levels. With increase in dietary Ca levels, the tibial breaking strength slightly increased. There were no significant differences in the tibial contents of ash, Ca and phosphorus among groups. In conclusion, eggshell quality, as measured by appearance, strength and thickness of eggshell, were influenced by dietary Ca content as expected (p<0.05). These results suggested that aged laying hens require relatively higher level of Ca than required levels from current Korean feeding standards for poultry.
authors.affiliation: Team of An Educational Program for Specialists in Global Animal Science, Brain Korea 21 Plus Project, Konkuk University, Seoul 05029, Korea.
authors.forename: S H
authors.initials: SH
authors.lastname: An
authors.affiliation: Animal Nutrition & Physiology Team, National Institute of Animal Science, RDA, Wanjugun 55365, Korea.
authors.forename: D W
authors.initials: DW
authors.lastname: Kim
authors.affiliation: Department of Animal Science and Technology, Konkuk University, Seoul 05029, Korea.
authors.forename: B K
authors.initials: BK
authors.lastname: An
keywords: Aged Laying Hens; Cracked Eggs; Dietary Calcium Levels; Eggshell Strength; Tibial Breaking Strength