With its high nutritional value, high protein and low tannin contents, cratylia is suitable for ruminant supplementation during the dry season (Andersson et al., 2007). It has been considered a reliable resource for silvopastoral systems during periods of scarcity in Mexico and in the Southern State of Anzoátegui in Venezuela (Valles-De la Mora et al., 2014; Rodriguez et al., 2002).
Palatability
Early reports noted that Cratylia argentea was a palatable forage readily consumed by cattle (Göhl, 1982). Sheep given immature cratylia had higher intake rate when the forage was wilted and dried than when fed fresh. When sheep were given the choice of selecting fresh or dried cratylia, they consumed more dried forage, regardless of maturity, age of the animals and previous experience with the forage (Raaflaub et al., 1995).
Digestibility
The in vitro DM digestibility of cratylia is highly variable, ranging from 27% to more than 90% (Andersson et al., 2006). An OM digestibility value estimated by the gas method in goats was relatively low (42%, Zhou et al., 2011). In vitro experiments reported enhanced ruminal fermentation when cratylia was combined with tanniferous shrub legumes and low quality grasses (Stürm et al., 2007). Cratylia in vitro effect on rumen fermentation resulted from an increased provision of fermentable nitrogenous compounds (Hess et al., 2006). The addition of cratylia to Brachiaria dictyoneura in experiments with RUSITEC (artificial rumen) increased the release of methane by 3-4 times (compared to forage alone) and resulted in a further higher nutrient degradation and higher rumen ammonia concentration (Hess et al., 2003). Due to its limited tannin content, the addition of PEG to assess the adverse inhibitory effect of tannin has been less effective for Cratylia argentea than for other browse species richer in tannins (Osuga et al., 2005).
Cattle
Dairy cattle
In Nicaragua, DM intake and milk production of dairy cows fed ad libitum on low quality diet of sorghum-silage were increased by the suplementation of cratylia (2-3 kg). Neither milk composition (milk fat, total solids, crude protein) nor organoleptic characteristics (smell, taste and colour) were altered (Sanchez et al., 2006). In Colombia, restricted grazing of mature and/or young cratylia by dairy cows did not significantly influence the production or composition of milk compared to grazing of Brachiaria decumbens alone. Only variation of urea levels in milk and blood were noticed, probably related to a rebalancing between the ammonium released in the rumen and the energy necessary for microbial synthesis (Aparicio et al., 2002). In Costa Rica, it has been shown that the form of presentation of cratylia influenced intake. Fresh foliage mixed with molasses increased the in vitro DM digestibility by 10%. Intake was 32% higher with foliage wilted alone and 43% higher with foliage mixed with molasses. The addition of cratylia compared to the addition of chicken litter had no effect on milk production. Milk composition was comparable in both cases (Ibrahim et al., 2001). In trials with milking cows, a mix of cratylia and sugarcane used as pasture supplementation resulted in a milk increase of 1.2-2.2 L/cow/day. The increase was positively related to cratylia proportion in the mix. Response to cratylia supplementation was limited when cows of minor production potential were utilised or when the basal grass diet had protein levels above 7%. Supplementation with cratylia silage increased milk production by 0.5-1 L/day (Cook et al., 2005).
Zebu cattle
In Colombia, in growing Zebu and crossbred Zebu x San Martinero bulls, supplementation with sugarcane and cratylia gave better weight gains when animals were grazing fertilized signal grass than when they were supplemented in a corral. Grazing animals also gave better results with supplementation than without (Rincon, 2005).
Sheep
There may be some difference in feeding sheep with young or mature cratylia. While wilting or drying mature cratylia did not affect intake when sheep were fed mature cratylia, these conservation processes increased the rate of intake when cratylia was cut at early stages. Sheep consumed more readily cratylia in the dry form than in the fresh one, irrespective of their previous consumption experience and their age. In Colombia, adult African hair-type sheep fed with low-quality herbaceous hay supplemented with cratylia, increased their OM and protein intake by 21% and 19% respectively, as well as ruminal fluid ammonia N concentrations. By another way, supplementation with S. saponaria increased (P < 0.05) dietary OM intake by 14%, and appears as a beneficial way to improve ruminal VFA profile, microbial efficiency, and duodenal flow of microbial protein. Otherwise few interactions between legume and S. saponaria supplementations were observed. Thus supplementation of S. saponaria fruits is a beneficial way for improving microbial efficiency not only for diets based on grass alone, but also for grass-legume diets (Abreu et al., 2004). In Colombia as well, the addition of cratylia to a low quality diet of Brachiaria dictyoneura was assessed in order to dilute tannin levels in the diet of sheep and improve their N utilisation. The addition of cratylia resulted in an apparent higher N digestibility, but intake and N retention were not significantly altered. Therefore it is important to consider not only the tannin levels but also the digestibility of the legumes used (Fässler et al., 1995).
