The effect of a bisphosphonate on bone volume and eggshell structure in the hen

Bisphosphonates, used in the prevention and treatment of osteoporosis, in man, can prevent bone loss in experimental models of osteoporosis in mammals. In egg-laying hens there is a high incidence of bone fractures which are due to osteoporosis. Alendronate, a bisphosphonate, was given to three groups of hens in mid-lay. Different doses of alendronate were given to each group and group 4 was a control. The birds were killed after 2 weeks of treatment. The hens receiving the highest dosage of alendronate (1 mg/kg every 2nd day) ceased laying and had reduced serum calcium concentrations. Lower dosages of alendronate (0.1 and 0.01 mg/kg every 2nd day) resulted in normal egg production and serum calcium concentrations. Egg shells with ultra-structural features indicative of reduced shell quality were produced by hens on the two higher dosages, but the egg shells from the controls and from the hens on the lowest dosage were considered normal. When alendronate was administered to hens in mid-lay there was no effect on trabecular bone volumes, but there was a reduction in mean medullary bone volume in some groups. In a second experiment, pullets were treated with alendronate (0.01 mg/kg twice a week) before the onset of lay. The pullets were killed after laying their first egg. In the pullets treated with alendronate, this protocol resulted in a significantly greater volume of trabecular (structural) bone at the onset of lay.