Red clover and ewe fertility – farmer-led trial

Background

For farmers, red clover offers fast growth, high protein and superior nitrogen fixation over white closer, cutting fertiliser costs. It boosts soil health, drought resilience and biodiversity. However, farmers often avoid grazing breeding ewes on it due to fertility concerns. Four farmers wanting to challenge this belief worked with ADAS as part of an Innovative Farmers trial to see whether red clover forage mixes do impact ewe fertility.

Why were sheep farmers advised to avoid red clover?

Conventional advice from vets has discouraged farmers from including red clover in swards grazed by ewes before or during tupping, or for more than a few months. This belief stemmed from research conducted in the 1960s and 1970s in the southern hemisphere, which found that phytoestrogens in red clover mimic oestrogen and adversely affected ewe fertility.

This research, conducted with 100% red clover swards, has limited relevance to UK systems where red clover is grown in mixed swards. Modern red clover varieties are also bred with lower phytoestrogen levels. No practical research existed that confirmed whether modern varieties are safe to graze during mating.

As long as this guidance remains unchallenged, the use of red clover-enriched swards is restricted to non-breeding livestock for extensive periods of the grazing season. This limits the use of legumes for sheep farmers and prevents them from realising the benefits of red clovers, such as drought tolerance, nitrogen fixation, and improved soil structure.

How the farmer-led trial worked

The participants were four farmers from the West Midlands and Mid Wales who already had red clover swards in place, along with breeding ewes. Each of the four farms has between 500 and 2,000 breeding ewes, with at least 160 of them for the trial.

The ewes

The chosen ewes were randomly divided into two sub-flocks, taking into account age, breed, and past performance. One half grazed on herbal leys containing red clover. The other half (the control group) grazed grass leys with no red clover. The two groups of ewes contained a similar mix of ages, body condition scores, and breeds.

The groups of ewes were merged afterwards to ensure consistent management for the rest of their pregnancies. Scanning results for both groups were recorded to track fertility.

Farmer interviews

Farmer interviews were conducted before the trial began to get baseline information on soil type, forage, and past sheep fertility. A second interview was conducted after the red clover grazing period to gather information on sward treatment, stocking rate, and grazing time before tupping.

Sward assessments

The sward height was measured using an AHDB sward stick in each red clover and non-red clover trial field three weeks before tupping and at the beginning of the mating season to determine the total availability of forage. Samples were also sent for lab analysis to determine the dry matter and nutritional content.

Further assessments were carried out to assess the quantity of red clover contained in the sward.

Results

On average across all the participants, the ewes in the control group scanned at 170%, while the ewes mated on red clover swards scanned at 181%. It is thought that the groups of breeding ewes that grazed the red clover swards achieved a higher scanning percentage due to improved availability and quality of forage before and during the mating period.

This higher scanning rate indicates that the inclusion of red clover within grass leys did not adversely affect ewe fertility.

It is hoped that the findings from this study will encourage more businesses to establish legume and herb-rich swards, benefiting from red clover’s additional advantages as well as generating additional income.

“The more red clover we can use, the better – it’s helped us to really cut back on nitrogen costs and it’s also good for drought resistance. Without legumes we would be looking at paying huge costs this year – fertiliser costs would have gone from £35,000 last year to £90,000 this year.”
Marc Jones, Powys

“We now finish as many lambs as possible on it and tup on it too. We now don’t buy in any nitrogen fertiliser or feed other than a bit of fodder beet, and my business is as resilient as it could be as a result.”
Tim Teague, Shropshire