Red clover is well known for its high protein and dry matter intakes resulting in excellent growth rates of livestock. But it does consist of phyto-oestrogenic compounds which have the ability to reduce ewe fertility. This reduces fertility in a number of different ways including, a change in the composition of the mucus secreted by the reproductive tract in the ewe. This mucus is responsible for sperm transport. Another reason is a reduction in ovulation rate, meaning if the ewe does conceive, the number of lambs will be lower.
Some points to consider with grazing red clover swards:
- Ewes prefer red clover to grass and will select it from a sward even if there is a only a small percentage in the ley. Inspect your swards for red clover 6 weeks pre tupping.
- There has been no effect found on tup fertility from eating red clover.
- Red clover has a higher oestrogen level in the spring and autumn, and is generally lower in the summer.
- Oestrogen levels are increased when the crop is stressed e.g. pest, disease, nutrient disorder or silage making.
- If ewes graze red clover leys over a 2-3 year period, there is a chance they may become permanently infertile.
- Grazing ewe lambs on red clover before tupping can cause a degree if infertility. This can be rectified after one month of grazing a sward with no red clover.
- Some plant breeders are selling red clover with a low phyto-oestrogenic content.
Kirsten Williams, email@example.com.
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