Red clover benefits
As a forage legume, red clover has the ability to fix nitrogen due to the presence of bacteria in the root nodules. During establishment and growth of red clover there is no requirement for nitrogen, reducing fertiliser costs. Both potassium and phosphorus are required at 70kg/ha or 56 units/acre for red clover but application should be guided by recent soil analysis. Red clover can be established in a wide variety of soil types however acidic, wet and shallow soils are not suitable. Red clover requires a soil pH of between 6.0 and 6.5 for successful establishment and growth, however it can tolerant a soil pH down to 5.5. Germination of red clover seeds or regrowth of red clover following winter dormancy will occur when soil temperatures reach 7ºC which is 2ºC higher than required for grass growth. This difference in soil temperature does impact the time of harvest for red clover which will generally occur three to four weeks later than harvesting of a grass ley.
Silage quality of red clover
Wilting is particularly important for red clover as the plant can be sappy and a 24 to 48 hours wilting time is recommended. However, it is important to note that the leaves can become brittle if over wilted and will potentially shatter during harvest impacting on the nutritional value of the silage. In the first year of a red clover ley and subsequent years, harvesting can occur up to three times a year depending on weather conditions and growth rates. The breakdown of protein in grass and other forage legumes can be quite significant during fermentation within the silo or clamp. Red clover has an enzyme called polyphenol oxidase (PPO) which reduces the breakdown of protein in the silo or clamp, therefore improving crude protein present in the silage and availability of protein in the small intestine of the cow. This may help to reduce the cost of protein supplementation. Crude protein content of red clover tends to be higher than grass silage, with values of between 170 and 210 g/kg DM. Red clover tends to have a ME content of 11.0 MJ/kg DM and a dry matter content of 200 – 375 g/kg.
Feeding red clover to dairy cows
There have been many studies which have compared feeding grass silage and red clover silage to dairy cows. Previous studies, (Van Ranst et al., 2011; Lee et al., 2009) found that cows fed red clover silage had similar levels of milk fat as cows fed grass silage. However, when the milk fatty acid profile was investigated there was a change in levels of polyunsaturated fatty acids (PUFAs) C18:2 n-6 (Omega 6) and C18:3 n-3 (Omega 3) which are beneficial for human health. Both fatty acids were found to be higher in cows fed red clover silage compared to cows fed grass silage (Lee et al., 2009). It has been suggested that the presence of PPO in red clover silage can provide these fatty acids protection from breakdown in the rumen by the microbes, allowing digestion in the small intestine.
A study by Moorby et al. (2009) investigated feeding dairy cows a TMR with different levels of grass and red clover silage. In table 1, the results of the study can be found including DM intake, milk yield, milk protein, milk fat, fatty acid contents of C18:2 n-6 and C18:3 n-3. Although milk fat content of the milk decreased as the amount of red clover silage was included in the diet, there was a significant increase in both C18:2 n-6 and C18:3 n-3. The researchers suggested that the effect on milk fat content may be due to a dilution due to the higher milk yields as there was no effect on milk fat yield for each diet.
|Red clover inclusion rate (%)
|Grass inclusion rate (%)
|DM intake, kg/d
|Milk yield, kg/d
|Milk protein, kg/d
|Milk fat, g/kg
|C18:2 n-6, g/100g
|C18:3 n-3, g/100g
In conclusion, red clover is a forage legume which can reduce the cost of fertiliser on farm due to its ability to fix nitrogen. Red clover silage tends to have high levels of crude protein between 170 and 210 g/kg DM, due to the presence of an enzyme which reduces the breakdown of protein in the silo or clamp. It has been shown to increase DM intakes, milk yields and PUFAs with the optimum inclusion rate of between 50 – 66% red clover silage mixed with grass silage.
References available upon request.
Cara Campbell, Cara.Campbell@sac.co.uk
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