Biomedical subjects

J L Saunders-Blades

Publications and source records attributed to J L Saunders-Blades.

2 recordsLinked to original sources

PubMed2004

Assessing bone mineral density in vivo: quantitative computed tomography.

Egg-laying hens require substantial amounts of Ca to support eggshell formation. Over time, structural bone is catabolized to provide some of the Ca required; the structural bone is not replaced. As the hen ages, this can eventually lead to osteoporosis. Quantitative Computed Tomography (QCT) is a nondestructive technique used to measure bone mineral density (BMD). QCT is used diagnostically in humans to assess osteoporosis; BMD determined by QCT is correlated with other, more invasive methods of bone mineral determinations, such as ashing. An x-ray is sent through a bone at multiple angles within a plane to generate a 2-dimensional image and a 3-dimensional calculation of volume and BMD. The technique allows resolution of total, trabecular, and cortical BMD and cross-sectional areas. The separation of bone types allows very precise measurements of the bone compartments most important in Ca supply for eggshell formation and bone strength. QCT has been adapted in our laboratory to measure BMD in vivo and ex vivo in poultry; values obtained for poultry bones are moderately correlated with destructive means of assessing bone quality such as breaking strength, ashing, and chemical bone mineral determinations. Thus, changes in BMD of individual birds can be measured over time; BMD at specific time points can be correlated with production parameters and eggshell quality traits. QCT is an effective technique to measure BMD in laying hens, which allows resolution of total BMD as well as cortical and trabecular BMD.

Aging↗

PubMed2004

End-of-cycle bone quality in white- and brown-egg laying hens.

Broken and weak bones of laying hens are major welfare concerns in the table egg industry. Bone quality at the end of lay of brown- (Shaver 579) and white-(Shaver 2000) egg strains were compared. Prior to the start of the experiment, the hens had been housed in laying hen cages (2/cage). At 423 d of age (60 wk + 3 d), 24 hens of each strain were selected and individually caged, and egg production records were kept until 462 d of age (the end of 65 wk) for a total of 39 d. Egg quality analysis was undertaken during wk 65 of age. Hens were killed at 66 wk of age (463 d), and carcass and reproductive morphology traits were measured. Femur and humerus mineral density were measured using quantitative computed tomography, and breaking strength was measured by an Instron Materials Tester. The white-egg strain produced 3.7% more marketable eggs during the experiment due to a 0.3 d shorter mean pause length in egg production. Eggs from the brown strain were 3.4% heavier, had 4.0% more eggshell, and had a higher specific gravity than the white strain eggs (1.077 and 1.072, respectively). Final BW was 330 g greater in the brown-egg strain. Total bone density of the femur was not different between the 2 strains but was greater in the humerus of the brown-egg layers. Total femur and humerus bone areas were greater in the brown strain than the white-egg strain. Bone breaking strengths of the brown-egg strain were greater by 22% (femur) and 18% (humerus) than in the white-egg strain hens. These results indicate that this brown-egg strain may be more resistant to weak and broken bones at the end of production than the white-egg strain.

Aging↗