Skip to main content
ARS Home » Research » Publications at this Location » Publication #162044
Title: COMPARATIVE ASSESSMENT OF BONE PARAMETERS AMONG WILD-TYPE, RESTRICTED OVULATOR, AND OUT OF PRODUCTION HENS

Author
item KIM, W. - PENN STATE UNIV
item FORD, B. - PENN STATE UNIV
item Mitchell, Alva
item ELKIN, R. - PENN STATE UNIV
item LEACH, R. - PENN STATE UNIV

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2004
Publication Date: 9/1/2004
Citation: Kim, W.K., Ford, B.C., Mitchell, A.D., Elkin, R.G., Leach, R.M. 2004. Comparative assessment of bone parameters among wild-type restricted ovulator, and out of production hens. British Poultry Science. 45(4):463-470.

Interpretive Summary: Bone metabolism in the laying hen presents opportunities as well as challenges. In addition to the cortical and trabecular bone present in the skeleton of other species, the laying hen skeleton contains a unique bone (medullary bone) in the marrow cavity and formed shortly before the onset of egg laying by the influence of estrogen. This bone cycles on a daily basis and contributes 35 to 40 percent of the calcium in each egg shell. Restricted ovulator (RO) hens could be a useful model for studying avian bone metabolism. RO hens are generally unable to ovulate due to a point mutation in the oocyte VLDL receptor gene whose protein product mediates the uptake of yolk precursors from the circulation. This study shows that 1) RO hens have greater plasma Ca, glycosaminoglycans, and keratan sulfate levels reflecting elevated levels of circulating Ca-binding yolk precursor macromolecules and intensive medullary bone formation, 2) RO hens have a better bone status indicating intensive medullary formation stimulated by increased plasma estrogen and the lack of cyclic Ca metabolism, and 3) dual-energy X-ray absorptiometry is a good tool for endpoint bone measurements.

Technical Abstract: Restricted ovulator (RO) hens are generally unable to ovulate due to a point mutation in the oocyte VLDL receptor gene whose protein product mediates the uptake of yolk precursors. Since RO hens do not have cyclic calcium metabolism associated with egg shell formation, they could be a useful model for studying bone metabolism. Blood was collected to measure plasma Ca, total glycosaminoglycans (GAG), keratan sulfate (KS), and hydroxyproline (HYPRO) from 17 wild-type (WT), 12 RO, and 6 out-of-production (OP) (hormonally quiescent) hens. Tibia, femurs, and humeri were collected from each bird to evaluate various bone parameters using conventional bone assays and dual-energy X-ray absorptiometry (DXA). Plasma Ca, GAG, and KS levels of RO hens were higher than WT and OP hens. RO hens had significantly higher humerus, femur, and tibia ash contents, femur and tibia percent ash, and humerus, femur, and tibia ash concentrations than WT and OP hens. Bone mineral content and density obtained with DEXA closely mirrored the results of conventional bone assays. Moreover, differences of mineral content and density among the treatments in femur and tibia, which contain medullary bone, were much greater than humerus which lacks medullary bone. Bone parameters of femur and tibia were highly correlated with each other whereas those of humerus were less highly correlated to femur and tibia. Correlation coefficients of humerus, femur, and tibia mineral content between conventional bone assay and DXA values were 0.942, 0.996, and 0.989, respectively. Mineral densities using DXA were also highly correlated to their ash concentrations (0.997).