Persian clover is a palatable forage, and more so than common forage species including perennial ryegrass (Lolium perenne), fescue (Festuca arundinacea), alfalfa (Simon, 1974) or forage rape (Kaur et al., 2010).
Pasture and fresh forage
Fresh Persian clover has an excellent nutritive value for ruminants, even better than that of red clover (Trifolium pratense) or alfalfa (Medicago sativa), due to a lower and poorly lignified cell wall content that makes it highly digestible (Kim et al., 2004; Singh et al., 1993). In vivo OM and protein digestibility of fresh Persian clover are in the 79-86% and 74-84% ranges respectively. Compared to Trifolium subterraneum, Trifolium resupinatum had a lower nitrogen digestibility because of a higher content of hemicellulosic polysaccharides (xylose and mannose monomers) (Li et al., 1994). The rumen DM, OM and protein degradability are also high (Cohen, 2001; McLaren et al., 1988). Wilting fresh forage from 12 to 20% DM decreased nutrient digestibility and milk production in dairy cows (Stockdale, 1993b).
The high degradability of Persian clover can become a problem when it is the only forage grazed by the animals, as it may result in a rumen pH lower than 6, decreased cellulolytic activity, and acidosis (Leddin et al., 2010). This risk is particularly acute when pasture availability is very high: a larger daily allowance leads to higher intakes and transit times, and animals are able to select the most nutritive parts of the plant, which are the most soluble with the least NDF content (Heard et al., 2006), without any change in chewing duration (Williams et al., 2005a; Williams et al., 2005b). Consequently, this causes a decrease in rumen pH accompanied by an increase in VFA concentration and a decrease in the C2:C3 ratio and in the cellulolytic capacity of the rumen (Stockdale, 1993c; Williams et al., 2005b). Animals grazing Trifolium resupinatum spent less time chewing than those grazing grasses such as ryegrass, which increased the risk of acidosis (Williams et al., 2000). Moreover, as with other legumes, the excess of nitrogen in the rumen may result in a wastage of energy, which should be avoided (Heard et al., 2006).
In dairy cows, combining fresh Persian clover with maize silage improved nutrient balance. The proportions of Persian clover and maize silage in the mixture depend on the physiological status of the cows and on their production level (Stockdale, 1994a; Stockdale, 1994b).
The OM digestibility of Persian clover hay is generally lower than that of fresh forage. For instance OM digestibility varied from 54 to 59% from early bloom to seeding and DM intake by sheep increased from 22 to 31 g/kg DM (Khazaal et al., 1993). When fed ad libitum, Persian clover had a nutritive value similar to that of Trifolium subterraneum in wool sheep in Australia (Doyle et al., 1988; McLaren et al., 1988). Trifolium resupinatum included in a total mixed ration at 40% of the diet was ingested at the same level as Trifolium alexandrinum by buffalo calves and had similar digestibilities for DM, crude fibre, but a lower protein digestibility (Kaur et al., 2004).
With an OM digestibility of 59% and a DM crude protein content of 8%, Persian clover straw had a better nutritive value than cereal straws and could meet the requirements of adult buffaloes, which can be interesting during periods of feed scarcity (Kaushal et al., 2006).