Red clover is a common forage for ruminants in temperate countries where it is used for grazing, hay and silage.
As other legumes, red clover leaves are highly prehensible, especially during the spring heading period (Dewhurst et al., 2009). A mixture of red clover and ryegrass is very palatable to cows and helps to mitigate the risk of bloat (Van Dorland et al., 2006; Charles, 1976). Red clover silage is highly palatable, more than grass silage but less than white clover silage (Steinshamn, 2010; Brink et al., 1988; Thomas et al., 1985; Steen et al., 1982).
Digestibility and degradability
The decrease of digestibility of red clover during maturing is lower for red clover than for grasses (Thomas et al., 1985). Red clover has a greater cell wall content than white clover and, therefore, a lower in sacco degradability and in vivo digestibility (Dewhurst et al., 2009). Compared to grasses, red clover has a higher rate of particle size reduction (Bowman et al., 1996) and a higher rate of degradation, linked both to its lower cell wall content and higher soluble carbohydrate content (Steinshamn, 2010; Moharrery et al., 2009). The differences in cell wall structure and degradation rate may explain the higher intake with red clover compared to grasses, as red clover has a lower rumen fill.
Effective nitrogen degradability was reported to be about 65-70% for fresh forage or silage, but only 60% for that stored in wrapped round bales (Aufrère et al., 2002; Marichal et al., 2010). However, there are differences between cultivars: in a study of 133 samples (16 to 21% DM protein), the nitrogen degradation rate varied from 0.088 to 0.146 and by-pass protein ranged from 29 to 41% (Broderick et al., 2004). During ensilage, red clover undergoes extensive protein degradation: the resulting high levels of quickly degradable nitrogen require carbohydrate-rich feeds in order to add energy to avoid inefficient nitrogen utilization and a large loss of N in the urine (Vanhatalo et al., 2009). However, supplementation of red clover with a high-protein ryegrass could increase nitrogen losses, which does not help to mitigate methane emissions (Van Dorland et al., 2007).
A pasture combining red clover, white clover, tall fescue, phalaris and cocksfoot was reported to be a good choice for Jersey cows and was of better nutritive value than one based on ryegrass and white clover (Thom et al., 2001). Milk from cows grazing or fed fresh forage, especially from species-rich grasslands or forage legumes, had a considerably higher ratio of unsaturated to saturated fatty acids, and a higher content of nutritionally beneficial trans-fatty acids (e.g. CLA, vaccenic acid) than milk from cows fed silage or hay (Kalac et al., 2010).
In a review of forage legumes (Steinshamn, 2010), it was noted that, at similar DM intake, dairy cows fed red clover silage produced a little less milk than those fed white clover silage. Cows on red clover silage diets had a milk fat content lower on average by 2.0 g/kg milk than cows fed grass silages, and milk protein content also tended to be lower. The milk protein decrease may be linked to the polyphenol oxidase enzyme, which produces phenols that bind to amino acids. Even if red clover causes a higher supply of amino acids to the intestine, sulphur-containing amino acids are less available than the other amino acids, and this imbalanced amino acid supply might explain the relative decrease in protein content compared to other sources (Vanhatalo et al., 2009).
Red and white clover grown in mixtures with grasses gave similar results for silage intake, milk yield and milk composition, but milk fat content of C18:3n-3 and C18:2n-6 was higher, and n-6:n-3 fatty acids ratio was lower on red clover diets (Steinshamn et al., 2008b). Partial replacement (40%) of grass silage with red clover silage increased yields of milk, protein and lactose, due to increased flows of microbial and dietary N entering the small intestine (Vanhatalo et al., 2006). Replacement of alfalfa with red clover increased feed and N efficiency, the digestibility of DM and cell wall components, and consequently the net energy for lactation. Nitrogen from red clover was better utilized when milk protein production was higher (Broderick et al., 2001; Broderick et al., 2000). Mixtures of red clover and maize silage (25:75 or 40:60) led to a significant increase in DM intake compared to grass silage (perennial ryegrass), and to a higher milk yield without altering milk composition. The N partition was more favourable to milk than to urine, due to an increased microbial protein synthesis permitted by the increased dietary starch provided by maize (Dewhurst et al., 2010).
The lower milk fat content resulting from legume-based diets (compared to grass-based diets), may be due to an increased supply of long-chain fatty acids to the mammary gland which inhibits the de novo fatty acid synthesis (Vanhatalo et al., 2007; Wiking et al., 2010). A second explanation might be the decrease in the molar proportion of rumen butyric acid, which is one of the main acids for the de novo synthesis (Vanhatalo et al., 2009). Red clover silage leads to reduced rumen biohydrogenation of 18:3 fatty acids, because the enzyme polyphenol oxidase, which is abundant in red clover, reduces lipolysis, a prerequisite of rumen microbial hydrogenation of unsaturated fatty acids (Lee et al., 2009b; Lourenço et al., 2008). Feeding red clover silage, especially at a young stage, increases α-linolenic acid (18:3n-3) in milk, which is beneficial to human consumption (Dewhurst et al., 2006; Van Dorland et al., 2008; Vanhatalo et al., 2007). In some studies, milk oxidative stability was lower for cows fed red clover diets, which was due to the increase in C18:3n-3 in milk (Havemose et al., 2006; Kalac, 2011). A solution to this problem is to supplement cows with Vitamin E (Al-Mabruk et al., 2004), even though clover silages are known to be among the most important sources of Vitamin E in organic farming (Beeckman et al., 2010). Replacing ryegrass silage with red clover silage did not modify the flavor of milk even when it decreased fat and protein concentration, and increased PUFA (polyunsaturated fatty acids) (Moorby et al., 2009). Substituting high quality ryegrass silage with red clover silage during the dry period had no influence on the performance of dairy cows in early lactation (Moorby et al., 2008).
Steers grazing mixtures of red clover and tall fescue had greater average daily gains and larger ribeye areas than those grazing tall fescue only. However, there was no difference in muscle fatty acids concentration (Dierking et al., 2010). Moreover, a pasture rich in red clover increased the PUFA:SFA ratio in muscle from cattle compared to cattle from pastures rich in white clover or perennial ryegrass (Scollan et al., 2006).
Red clover hay associated with tall fescue for winter grazing, and Caucasian bluestem (Bothriochloa caucasica) for summer forage was found to be a very valuable supplement for stocker steers in the Southern USA (Allen et al., 2000).
Wilted red clover silage was fed to fattening bulls, even though it has a lower feeding value than maize silage, resulting in longer fattening periods, but it saved about 120-130 kg concentrate/head. Red clover silage, treated with formic acid at 3 L/t and supplemented with 0.5 kg/d of soybean meal, achieved the same level of performance as a maize silage-based diet (Weiss et al., 1993). The fatty acid profile of meat from cattle offered clover silage was better than that from cattle offered grass silage, because of an increase in the content of C18:3n-3, total n-3 fatty acids and total PUFA (Lee et al., 2009a).
Pure red clover swards had a lower nutritive value than white clover swards for growing sheep (John et al., 1981), but better than that of perennial ryegrass (Lolium perenne). It gave live-weight gains in lambs that were 70% greater than those obtained with ryegrass (Kemp et al., 2010). Red clover mixed with chicory, plantain (Plantago lanceolata) and white clover improved production of multiple-bearing ewes and their offspring compared to a ryegrass-dominant sward: animals were heavier, had higher body condition scores and produced more milk. Their lambs were heavier at birth and gained more weight during their first two months, which demonstrated that a herb sward mixture can improve the performance of multiple-bearing ewes as well as lamb performance compared to a ryegrass-dominant sward (Hutton et al., 2011).
Due to its high palatability, red clover silage fed to finishing lambs resulted in greater energy intake, faster growth rate, better condition score and a reduction in time to slaughter than lambs offered alfalfa or ryegrass (Speijers et al., 2004). Red clover silage replaced ryegrass silage in a way beneficial to fattening lambs (Speijers et al., 2005b). Red clover fed to ewes before lambing resulted in increased DM and live-weight gain for ewes and higher growth rates during the first 12 weeks for the lambs, compared to perennial ryegrass silage. However, red clover did not improve litter size (Speijers et al., 2005a).
Red clover, either alone or mixed with grasses in pure swards, can be used as a potential crop with a high protein content for dairy goats (Kravale et al., 2001). It can be used in zero-grazing (Masson et al., 1980). With alfalfa and ryegrass, red clover is considered one of the forages with the highest voluntary intake and milk yielding capacity for goats in temperate climates (Morand-Fehr et al., 1980), and a valuable source of protein for goats in cold arid zones such as Ladakh (Inda) (Mondal, 2009).