Digestibility and degradability
Dry matter digestibility of Sesbania species is superior to that of most other tree and shrub legumes (Gutteridge et al., 1994). Sesbania sesban foliage has rapid and extensive rumen degradabilities (Kaitho et al., 1998b). In vitro DM digestibility (IVDMD) was found to be about 75% (Gutteridge et al., 1994). In vivo DM digestibility measured in goats ranged between 66 and 71% (Singh et al., 1980 cited by Gutteridge et al., 1994). When sesban foliage was used as a supplementary protein source in roughage-based diets, it had a positive effect on the rumen degradation of DM, OM, CP, CF and NDF (Tessema et al., 2004; Kamatali et al., 1992). Many experiments have also shown that sesban foliage increased the digestibility of DM, OM and CP in cattle, sheep or goats fed on a roughage basal diet (Nguyen Thi Hong Nhan et al., 2009; Manaye et al., 2009; Mekoya et al., 2009b; Melaku et al., 2005; Sampathi et al., 1999). However, accessions of sesban rich in condensed tannins were reported to decrease NDF digestibility of the diet (Kaitho et al., 1998a).
Sesban foliage has a positive effect on N retention whether it is measured in cattle, in sheep or in goats. It often causes higher N retention than other forage tree legumes (Wambui et al., 2006; Sampathi et al., 1999; Umunna et al., 1995).
Sesban offered as supplementary protein to cattle fed tropical roughages can be included at up to 25% of the diet (Tessema et al., 2004). In Vietnam, sesban foliage supplementing crossbred cattle grazing native pasture (Hymenachne acutigluna and Paspalum atratum) yielded superior growth rate (+20%) than when Hymenachne acutigluna was the sole diet (Nguyen Thi Hong Nhan et al., 2009). In Queensland (Australia), cattle grazing Signal grass (Brachiaria decumbens) and sesban foliage had a greater growth rate (about 80%) (Gutteridge et al., 1991).
However, in an attempt to replace noug oilseed cake (Guizotia abyssinica) in lactating crossbred dairy cows, the inclusion of sesban foliage resulted in lower feed intake and lower crude protein digestibility, which led to insufficient digestible protein and lower milk yield (Khalili et al., 1992).
Sheep and goats
Sesban is palatable to sheep and goats. It ranked third in palatability after cajan pea (Cajanus cajan) and leucaena when offered to Djallonke rams and West African Dwarf goats (Karbo et al., 1996). Sesban can be used as supplementary protein to roughage-based diets or to concentrate mixtures for sheep and goats. Level of inclusion for optimal growth rate or milk yield was about 30% of the diet when it was used as supplement to teff straw (Eragrostis tef), Napier grass or sorghum stover (Mekoya et al., 2009c; Manaye et al., 2009; Mengistie Taye, 2009; Sampathi et al., 1999; Kaitho et al., 1998b).
The effects of feeding sesban foliage to sheep and goats have been studied for a long time and are still much debated. Though sesban foliage was shown to have high in vitro and in vivo digestibilities as well as positive N balance, its effects on feed intake (DM intake) are not consistent between authors. Some studies report higher feed intake or DM intake when sesban foliage is used as supplementary protein in roughage-based diets even at high levels of inclusion (Mengistie Taye, 2009; Manaye et al., 2009; Mekoya et al., 2009b). Earlier studies have reported a negative effect of sesban on diet DM intake, especially when it was fed at high levels (1.3-1.5% LW) or when the sesban accessions used were low in tannin (Kaitho et al., 1998a).
Growth rates achieved in feeding trials with sesban are often not as promising as with other forage tree legumes that have lower in vitro and in vivo digestibilities (Kaitho et al., 1998a). Large differences in growth performance have been found in animals fed sesban foliage.
In sheep, daily weight gains from 35 g/d to 108 g/d have been reported (ILCA, 1987; Reed, 1988 cited by Gutteridge et al., 1994; Manaye et al., 2009). Ewes gained 23-24 g/d when they were fed different levels of sesban foliage (Melaku et al., 2004; Mekoya et al., 2009b). Supplementing lactating ewes with sesban foliage did not improve daily gain but had a positive effect on milk yield (+13%) and on the weight gain of lambs (Mekoya et al., 2009c).
Goats fed sesban as sole forage for 8 weeks gained an average of 17.1 g per day (Singh et al., 1980 cited by Gutteridge et al., 1994), while goats fed teff straw (Eragrostis tef) and supplemented with sesban gained only 4 g/d (ILCA, 1987 cited by Gutteridge et al., 1994).
The effects of sesban feeding on reproductive performance are also debated. Sesban was reported to have deleterious effects (degeneration and necrosis) on the seminiferous tubules of male sheep and goats (Woldemeskel et al., 2001). Prolonged and uninterrupted sesban intake may also hinder sexual development (scrotum circumference changes) and live-weight gains in male sheep and goats (Kaitho et al., 1998c). Supplementing ewes with sesban could compromise oestrus at high levels of inclusion (13.3 g DM/kg LW) and could cause abortion or deaths of pregnant ewes (Melaku et al., 2004). However, a series of studies from Mekoya et al. in 2009 showed that long-term feeding of sesban foliage resulted in improved reproductive performance in both male and female sheep. It was also shown that feeding sesban from post-weaning to puberty reduced the age of puberty and improved sexual development (Mekoya et al., 2009a; Mekoya et al., 2009b).