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Beware red clover

20 September 2016

Grazing red clover or eating red clover silage at tupping time can affect ewes fertility.  Breeding ewes should avoid eating red clover for six weeks before and after tupping.

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,

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