Vaginal prolapses tend to occur in the last month before lambing (occasionally they will occur after lambing). A normal incidence is a maximum of 1 ewe in 100, or 1%, if you have more bearings than this you need to consider the following factors.
The old fashioned dogma was that you should not feed ewes too much in the month before lambing as it increases the incidence of vaginal prolapse. This is not true, however if you feed very poor quality bulky food, you may get more prolapses. Also, if the ewes are on a “feast and famine” diet, i.e. get very hungry, then fill up rapidly, you will see more prolapses.
There is no single cause of vaginal prolapses, but there are a number of factors which increase the risk:
- Breed – more common in highly prolific breeds.
- Number of lambs – there is a 5 x increased risk in ewes with twins and an 11-12 x increased risk in those with triplets when compared with ewes only carrying a single lamb.
- Age – more common in older ewes.
- Prolapse history – 35-40% of ewes who have had vaginal prolapses before lambing, have them in subsequent pregnancies.
- Nutrition – break feeding where ewes become very empty and hungry, and feeding poor quality roughage eg. silage, long poor quality grass, poor quality hay.
- Lack of exercise – for example in housed ewes or when ewes are lame.
- Excessive body condition – not uncommon on small blocks where ewe condition is not controlled.
According to the new Animal Welfare regulations, bearings in ewes may be replaced by competent people as long as the correct equipment is used (bearing retainer) and veterinary advice is sought for any complications.