Digestibility and energy content
There are few data reporting the digestibility of Stylosanthes hamata. Using an equation obtained on other Stylosanthes species (OMD % = 67.2 – 0.214 NDF % DM + 0.335 CP % DM; N=19, R²=0.40, RSD=3.1; Sauvant, 2012), the average OM digestibility of Stylosanthes hamata forage can be estimated at 62% (55-68%), corresponding to an ME of 8.8 MJ/kg DM (7.5-9.9 MJ/kg DM). In fresh Caribbean stylo harvested at 80 days (50% flowering), DM digestibility was 65%, and crude fiber 34% DM (Nandanwar et al., 1991). One study on Stylosanthes hamata mature forage (called “straw” in the report and containing about 7% DM as protein) indicated a DM digestibility of 51% (Misra et al., 1997). Digestibility of NDF is probably the limiting factor: an in sacco digestibility (48 h) of NDF was found to be only of 41% (for a sample containing 55% NDF DM; Kennedy et al., 1999). Besides, indigestible NDF was associated with a limited buffering capacity in the rumen (Bandla Srinivas et al., 2010). As noted in Nutritional attributes above, the digestibility of Carribean stylo hay decreased between 90 and 150 days after sowing (Singh et al., 2001).
Association with grasses and other crops
Stylosanthes hamata is able to improve tropical grazing systems (Cameron, 2010). Various studies in India and West Africa have shown that oversowing grasses with Caribbean stylo removed the N limitation, resulting in a dramatic increase in stocking rates and live-weight gain per ha (Winter, 1989).
In India, feeding a 3:1 mixture of Cenchrus ciliaris and Stylosanthes hamata as hay or fresh grass, to adult male goats, was better than feeding Cenchrus as the sole fodder (Ravi et al., 2000). Supplementation of a natural grass pasture (Cenchrus ciliaris) with legume (Stylosanthes hamata) and tree leaves (Albizia lebbeck) improved the nutrient digestibility and utilization in sheep (Pailan et al., 2003). In Côte d'Ivoire, a well-managed association of Guinea grass (Megathyrsus maximus) and Stylosanthes hamata was found superior to natural grassland. The sward was more resistant to close grazing, had an increased nutritive value, and could support higher stocking rates (César et al., 1999). In Cameroon, Stylosanthes hamata and Calopogonium mucunoides were planted and divided into cutting, grazing and control subplots: legume seed production was found feasible and manageable under an integrated dairy (zebu) production system (Asongwed-Awa et al., 2002).
In Nigeria, West African Dwarf sheep fed forage from Andropogon tectorum intercropped with Stylosanthes hamata at different inter-row spacings (0, 2.5, 5.0 and 7.5 m) had the highest final weight gain and average daily gain at a spacing of 2.5 m (Aderinola et al., 2010). Studies were also carried out in Mali to introduce Stylosanthes hamata and improve sheep and cattle production (Coulibaly et al., 1996). In Thailand, the intercropping of Caribbean stylo and cassava was able to triple the net income compared with cassava alone (Gibson, 1987). As noted in Forage management, Stylosanthes hamata can be grown under orchard trees. In India, mixtures of Stylosanthes hamata and Cenchrus ciliaris in mango and sweet orange orchards resulted in higher live weights in lambs compared to those grazing solely on natural pasture (Ramana et al., 2011).
Supplementation with Carribbean stylo can be useful in the case of nutrient-poor diets. In India, Caribbean stylo hay and Leucaena leucocephala leaf meal improved intake, digestibility and utilization of nutrients in sheep fed Cenchrus ciliaris hay (Pailan et al., 2005). The nutrient digestibility of rice straw by bulls was increased with supplementation with Stylosanthes hamata (Reddy, 1998).
In Northern Australia, the introduction of legumes, including Stylosanthes hamata, resulted in a significant increase in beef cattle production, especially when P was added to the soil (Coulibaly et al., 1996). Cattle grazing Stylosanthes hamata showed less weight loss in spring than cattle grazing grass, though there was a rapid weight loss in early summer (McKeague et al., 1979). In steers grazing native pastures or pastures oversown with Caribbean stylo, annual live-weight gain was related to the duration of green forage availability, the amount of Stylosanthes hamata in the pasture, and herbage utilization rate (McCaskill et al., 1993).
In India, under rainfed conditions, Stylosanthes hamata containing 13.4% DM as protein, allowed a live-weight gain of 180 g/d in heifers (Nandanwar et al., 1991). In the seasonally dry tropics, where stylo leaf can contain less than 7% DM as protein, the dry winter season grazing may be unable to sustain steer live weights even on stylo dominant pastures. Under these conditions Caribbean stylo pastures may require protein supplementation to prevent weight loss in the dry season (Hall et al., 2004).
In dairy buffaloes in India, 25% of concentrate (DM basis) was replaced by Caribbean stylo meal without affecting milk yield and composition in lactating buffaloes (Pailan et al., 2010). In Cameroon, with dairy cows grazing legumes intercropped with maize, cows fed Stylosanthes hamata gave 35% more milk compared to cows grazing Calopogonium mucunoides or Macroptilium lathyroides (Asongwed-Awa et al., 2002).
Sheep and goats
In Nigeria, the association of Stylosanthes hamata with Guinea grass was a better option for improving the feed quality of forage diets for goats than direct application of inorganic fertilizer at 200 kg/ha N to the pure grass (Bamikole et al., 2001). Also in Nigerian trials with grazing goats, Stylosanthes hamata established rapidly, but it was necessary to maintain good pasture conditions from the second grazing or cropping season (Iji et al., 1995). In Mali, studies in the early 1990s showed that Stylosanthes hamata could increase sheep production by 10 kg/ha (unfertilized pastures) and by 29 kg/ha with added P (Coulibaly et al., 1996).
In India, feed blocks based on Stylosanthes hamata were sufficient for maintenance requirement of sheep and goats (Das et al., 2007). Sheep and goats could be maintained with acceptable growth rates on silvopastoral systems. Stylosanthes was the preferred plant species in mixed species pasture (Rai et al., 1998). Lambs grazing on a silvopastoral system and supplemented with either concentrate or Stylosanthes hamata had higher average daily gains and better feed efficiency than those that were not supplemented (Rao et al., 2007).