Narbon beans (raw or processed) and forage can be fed to ruminants (Selmi et al., 2010; Chiofalo et al., 2007; Hadjipanayiotou, 2003; Yu et al., 2001; Jacques et al., 1994; Karabulut et al., 1989).
Narbon beans can be used in ruminant diets as a partial substitute for soybean meal or legume seeds such as pea, common vetch and lupin (Hadjipanayiotou, 2003). However, performance results are variable and deleterious effects have been noted in sheep and dairy cows (see below). Narbon beans are digestible: reported in vitro (OM digestibility 88%) and in vivo digestibilities (78% for DM, 80% for OM and 75% for protein) are high (Hadjipanayiotou, 2000). The protein is highly degradable in the rumen (70-80% effective degradability). GEC may be a source or sulphur-containing amino acids for ruminants (Enneking, 1995).
Calves can be fed on crushed Narbon beans once they become acclimatized to the distinctive flavour. Narbon beans should not be fed to dairy cows as they produce an off-flavour in milk (Mateo-Box, 1961).
Sheep and goats
Narbon beans are a valuable supplement for roughage-based diets or as a component of concentrates for sheep feeding (Yu et al., 2001; Jacques et al., 1994; Kansu, 1961). Mature Merino wethers fed on Narbon beans (1% or 2% BW/d) had higher growth rates (128 g/d vs. 58 g/d at 1% BW and 99 vs. 90 g/d at 2% BW) than unsupplemented wethers (Jacques et al., 1994). When Narbon beans were compared to peas as a supplement (1% or 2% BW/d) to pasture, intake was slower and the highest performance was obtained at the lower inclusion rate (Jacques, 1990 cited by Enneking, 1995). It was hypothesized that the slower intake resulted in more stable rumen conditions and subsequent greater growth rate (Jacques et al., 1994; Jacques, 1990 cited by Enneking, 1995). Lambs fed on a roughage-based diet and supplemented with raw or roasted Narbon beans (15% DM basis) had significantly higher DM and OM digestibilities and higher daily gain. Feed conversion ratio was lowered and meat quality was unaffected, though lambs fed on roasted Narbon beans had a slightly higher dressing percentage and enhanced flavour and aroma (Yu et al., 2001). Narbon beans offered to growing lambs as a soybean meal replacer grew at a similar rate as those receiving the soybean meal (Hadjipanayiotou, 2003). There have been contradictory results on the effect of Narbon beans on wool production (growth rate and quality). Six-month old Suffolk x Merino wethers fed on Narbon beans yielded less wool than control sheep. It was, therefore, recommended that Narbon beans were not fed to wool-producing sheep (Allden et al., 1980). However, a later experiment with Merino wethers showed that wool growth rate remained unaffected by Narbon beans (Jacques et al., 1994). The occasional deleterious effects of Narbon beans on sheep performance were not observed in goats (Hadjipanayiotou, 2003).
Information on Narbon vetch forage is limited. It can be grazed or offered as hay or silage. The plant contains less fibre and its dry matter is more degradable than that of common vetch and woolly pod vetch (Vicia villosa) (Rahmati et al., 2012). Reported values for in vivo OM digestibility are rather high (70-80%) (Alibes et al., 1990; Neumark, 1970), but an in vitro DM digestibility value was lower (55%). The digestibility of the forage declines rapidly as the plant matures and its fibre content and lignification increases (Rahmati et al., 2012). Narbon vetch straw had low in vitro and in vivo digestibility values (less than 50%) (Hadjipanayiotou, 2000).
Finishing Charolais bulls, supplemented with 10% fresh Narbon vetch forage, as a partial substitution for soybean meal, had similar daily weight gains and feed conversion ratios as the controls (Chiofalo et al., 2007).