Monday, October 1, 2007

No link between Ca and vaginal prolapses

A vaginal prolapse is a protrusion of the vagina through the vulva. In New Zealand, it occurs on-average 13 days before lambing and is estimated to cost the New Zealand sheep industry $30-50 million per year. It is a troublesome problem in many U.S. sheep flocks. It is less common in goats.

ewe with vaginal prolapseCalcium (Ca) status has been implicated as one of the causes of vaginal prolapses, so New Zealand researchers conducted a series of experiments to evaluate the role of Ca and the incidence of vaginal prolapses in ewes.

In one experiment, researchers monitored the calcium status of old twin bearing ewes under normal commercial conditions. They sampled the ewes' blood at 60, 30, and 7 days prior to lambing. While 11 to 41 percent of the ewes had marginal serum Ca and magnesium status 60 and 30 days prior to lambing, no relationship was found between serum minerals and the incidence of vaginal prolapses.

In the second experiment, the researchers manipulated the Ca status of twin bearing ewes in flocks with a history of vaginal prolapses. However, neither the feeding of anionic salts in mid-pregnancy (to reduce urine losses of Ca) nor Ca or vitamin D supplements in late pregnancy consistently changed serum Ca concentration or the incidence of vaginal prolapses.

The researchers concluded that there is a strong "environmental" component associated with vaginal prolapses, not associated with feeding level; and that "the factors or combination of factors which make up this environmental component remain frustratingly elusive."