Red Clover as a home-grown protein in sustainable sheep systems
26 March 2025Increasing the amount of forage-based protein that can be grown on farm is a key way to address the UK’s protein deficit and reduce reliance on imported protein sources. Forage legumes such as white and red clover are important species in providing sustainability in the sheep sector. This guide will focus on the use of red clover in sheep systems including: nutritional value, establishment and management, and challenges with the crop.
The UK livestock industry is under increasing pressure to reduce reliance on imported protein sources, mainly soya. This is due to the concerns associated with deforestation and conversion of land for soya production in South America. As well as the large carbon footprint associated with feeding soya, the price volatility is another major concern with prices hitting over £570/tonne in 2022.
In addition, reducing the use of synthetic fertiliser is a commitment Scottish Government made in the 2018 “Climate Change Plan”. With synthetic nitrogen (N) fertiliser accounting for 25% of the greenhouse gas emissions from agricultural soils. This is also another high input cost that is vulnerable to price volatility, as again was demonstrated in September 2022 when the price to EU farmers increased by 149% compared with September 2021.
Using red clover as a source of homegrown protein
Red clover (Trifolium pratense) is a high quality, high protein crop, used to primarily to make silage and for grazing. Studies have shown red clover can increase lambs liveweight gains and reduce time to slaughter. It is a short-lived perennial herbage legume that typically persists for 2-4 years, depending on management and variety. However, there are newer varieties showing persistence of up to 5 years, AberClaret is one example with more new varieties in development. Long-term plots at IBERS are now showing the results for longer-lived varieties, with fourth -year data revealing new varieties producing up to 14 tonnes of dry matter per hectare. Therefore, problems with persistency should improve very soon as these newer varieties become available.
Growth habit and nitrogen fixation:
Red clover has a single growing point, the crown which stores nutrients and from which stems and a deep tap root grow from. Due to the prostrate growth habit of red clover it requires different grazing management to white clover to promote its persistency in swards. The growth habit of red clover makes it capable of high yields, with quotes of around 10-12tDM/ha in upland areas and up to 12-15t DM/ha in fertile areas. They also have a high tolerance to drought but are less tolerant to grazing. As the plant grows from the crown, if this is damaged by machinery or grazing the plant too hard it will die and persistency will be poor.
One of the primary benefits of red clover is the ability to capture nitrogen from the air and feed it into the soil and surrounding plants. Typically, it takes around 1 year from establishment for the red clover to fix 150-250 kg N/ha, another reason why longer-term leys (4-5 years) should be considered.
Top tips for establishing and growing red clover:
Red clover is typically grown in a mixed sward, however, it can be grown as a monoculture.
- Aiming for a clean, firm, fertile seedbed. If it has been in arable beforehand then fertility will typically be lower, then if going from grass.
- Apply phosphate and potash if soil indices are below 2.
- Weed control is critical. Achieving a clean seedbed is important to avoid competition from weed species during establishment.
- There are few herbicides available which are clover safe. One recently approved clover-safe spray available in the UK and Ireland is ProClova XL®, and while it can be used on red clover, it is important to note that it cannot be used until a year after the red clover has been established.
- Soil pH of 6.0- 6.5 is optimal. Clover will not fix atmospheric N if the soil pH values are below 5.0. If ground conditions are favourable apply limestone 2-3 weeks before spring N application to fields destined for silage.
- Do not sow the red clover seed too deep. If the seeds go below 10mm below they might germinate but they will not grow up and get established. The optimum seed depth is 5-10mm.
- Red clover is less suited to stitching into grass compared to white clover. Red clover will grow where it falls, therefore if the distribution of the seed is done poorly e.g. patchy or too heavy on one side of the field compared to the other it will stay that way.
- Less tolerant of N fertiliser than white clover. Apply N fertiliser to soils with low N status, but only up to 50kg N/ha.
- Need warm soil temperatures (8⁰C compared to 5ºC for grass), this will usually occur around late April – early May required for germination and kick starting a good flush of growth. The best time to sow is from April to late July.
- Typical seed mixtures:
- Mixed swards use 21-22kg/ha (8-9 kg/acre) of grass and 7-8kg/ha (4kg/acre) of red clover.
- Monocultures use 15kg/ha (6kg/acre)
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Silage management for red clover:
- Red clover only grows from its crown so this must be protected during cutting. Do not cut too low, aiming for around 7-8cm.
- Cut at the red bud stage just before flowering in mid-May for optimal crop yield and crude protein levels.
- Red clover leys suit a multi cut system, this helps to maintain clover content. In a mix sward the first cut will contain more grass than subsequent cuts as the clover starts to increase later in the season.
- Typically cut at 6-8 weeks intervals but can be as frequent as every 5 weeks. Yield tends to be around 13-14 t DM/ha or for upland sites around 10t DM/ha.
- To avoid leaf shatter use a spread mower rather than tedding to get a rapid wilt (wilt up to 48 hours), aiming for a dry matter of around 30%.
- Graze autumn regrowth lightly to finish lambs maintaining height of aftermath above 6cm.
- The water-soluble carbohydrate content of red clover (as shown in figure 2) is lower than a perennial ryegrass silage therefore using an additive is beneficial to ensure a rapid drop in pH and good fermentation.
- During ensiling and compact thin layers to expel as much air as possible and achieve a high forage density and ensure the clamp is well sealed.
- Traditional silage analysis by NIR tend to not be calibrated to deal with red clover silages (above 15% clover content), therefore it is advisable to perform a wet chemistry analysis on the protein content to ensure this is accurately measured, otherwise it could be underpredicted by grass silage calibrations.
Advice on grazing management of red clover can be found here: Grazing to Promote Red Clover
Nutritional value and performance on red clover:
Nutritionally red clover is known for its high protein content, reducing reliance on protein concentrates. The protein in red clover is concentrated in the delicate leaf structure, hence why care must be taken during ensilage to avoid “leaf shatter” during wilting and harvesting. Red clover contains a high level of naturally occurring polyphenol oxidase (PPO) enzyme. This plays a very important role in reducing protein degradation of red clover silages post-harvest and increasing protein utilisation by sheep when ingested.
Inefficient use of dietary forage protein by ruminants during digestion results in a high loss of nitrogen from the system, causing a negative effect both financially and environmentally. PPO releases quinones that bind to the protein in red clover and reduce the degradability in the rumen. This in effect allows protein to bypass the rumen and be absorbed in the small intestine, improving protein utilisation. The action of PPO is what causes the dark brown appearance of the red clover during ensilage.
Although red clover is not known to to be a high energy (digestible) forage, there have been many studies to show the improved performance of ewes in late pregnancy and finishing lambs fed red clover silage. One study by McGrane et al. 2023 showed the increase in performance between lambs fed a mixed sward of perennial ryegrass and red clover, compared to a pure perennial ryegrass sward. The mixed sward achieved an overall higher liveweight gain over the lifetime of the lamb (+31 g/day) and a reduced number of days to slaughter (-28.6 days) compared to the lambs fed perennial ryegrass.
Most of this benefit is due to the higher intake of red clover silage due to its high palatability and structure. Unlike the tough fibre in grass, the reticular vein structure of red clover allows it to breakdown more rapidly in the rumen into small particles. This rapid breakdown and faster rate of fermentation results in higher intakes. For example, sheep grazing red clover dry matter intakes can be up to 4% of their bodyweight compared to 2-3% for normal grass swards. There was also significantly less concentrate fed on the mixed sward.
Figure 1: Nutritional value of average grass silage and red clover silage
| Nutrient | Grass silage | Red clover silage |
|---|---|---|
| Dry matter (%) | 25-35 | 25-30 |
| D Value (%) | 65 | 60-70 |
| Metabolisable energy (MJ/kg DM) | 10.5-11 | 9.8-11.4 |
| Crude protein (% DM) | 10-14 | 16-21 |
| Water soluble carbohydrayes (% DM) | 15.5 | 9.2 |
| pH | 4.2-4.5 | <5 |
Source: Adapted from AHDB and SAC Consulting data
Figure 2: Lamb performance on perennial ryegrass vs a mixed perennial ryegrass and red clover sward
| Perennial ryegrass +Red Clover | Perennial ryegrass | |
|---|---|---|
| Birth – weaning average daily gain (g/day) | 251 | 237 |
| Weaning weight (kg) | 31.1 | 29.5 |
| Weaning – slaughter average daily gain (g/day) | 162 | 133 |
| Lifetime average daily gain (g/day) | 213 | 182 |
| Days to slaughter | 199.7 | 228.3 |
| Concentrates fed/ lamb drafted (kg) | 2.9 | 14.2 |
Source: adapted from McGrane et al. 2023
Important Considerations:
Fertility – avoid feeding either side of tupping:
Historically advice has been to avoid feeding red clover (fresh or ensiled) to breeding ewes 45 days either side of tupping. Red clover contains phtyoestrogens (like other legumes), these are a group of naturally occurring plant derived compounds which have the ability to cause oestrogenic and/or anti-oestrogenic effects in livestock. Phytoestrogens mimic actions of oestradiol but are not identical so may not affect behavioural oestrus. The main phytoestrogen in Red Clover is Formononetin. Formononetin is metabolised by micro-organisms in the rumen and the product of this, Isoflavan equol, directly causes infertility.
The level of phytoestrogens in the red clover depends on the variety. Stress during the growth period is also thought to increase the levels of phytoestrogens. Some recent on farm trials have shown that red clover has been successfully grazed pre/post-tupping without having an effect on fertility, these swards contained low phytoestrogen varieties and were less than 30% clover, therefore caution is still required.
Bloat – less so than white clover:
Bloat is a build-up of gases caused by the rapid breakdown of the clover protein. There appears to be less risk of bloat when feeding red clover compared to white, but care should still be taken when introducing it particularly on a monoculture ley.
There are some management strategies to reduce the risk:
- Risk is increased when grazing in wet conditions. Once ground conditions become to wet grazing should cease to avoid poaching and damage to the crown. In cases of early dew, or damp take care and wait until midday to graze if possible when dew has lifted.
- Limit access when first introduced to the field by strip grazing.
- When introducing stock do it after they have been fed to avoid them gorging. Ideally feed them a fibre source such as hay, or straw to help slow down flow rate through the rumen.
References:
Ensuring availabilty and affordability of fertilisers
McGrane et al. 2023. The effect of the addition of a companion forage to a perennial ryegrass sward on ewe and lamb performance Livestock Science.
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