Ewes in extra good condition are most prone to bearings, but ewes in lean condition are susceptible too. For the farmer, it is distressing and frustrating to see productive ewes develop bearings. There can be major losses in terms of treatment costs and deaths of ewes and lambs.
Bearings usually occur just before but sometimes after lambing.
In untreated ewes, lambing is impossible, infections develop and deaths occur. The cause of bearings is complex. A major factor is increased pressure in the abdomen, caused by a uterus full of lambs, a full rumen and sometimes a full bladder and a lot of abdominal fat. Other factors include slackness of the ligaments around the birth canal, sometimes associated with poor nutrition. There have been suggestions that low magnesium status and possibly low calcium status may be involved.