The potential benefits of ensiling the forage legume sulla compared with pasture

Abstract

With high dry matter yields of high quality forage, high soluble carbohydrate levels and a suitability for harvest by cutting and removing, the forage legume sulla (Hedysarum coronarium) has the potential to be an important silage crop in New Zealand. In three experiments the ensiling potential of sulla was compared with conventional pasture using a mini-silo system which allows for rapid evaluation of forages using 3-4 kg of herbage. Experiment 1 evaluated the effect of increasing the proportion of sulla in pasture silage (0/100, 25/75, 50/50, 75/25 and 100/0 sulla/pasture). The principal findings were that increasing sulla content of the silage decreased (P<0.001) ammonia content from 5.9% of total N to negligible detectable levels, and increased (P<0.0001) lactic acid content of silage from 3.3% to 9.9% of dry matter (DM) which resulted in a lower final pH (4.9 vs 4.0; P<0.0001). Experiment 2 examined the rate of ensilation of pure sulla and pasture after 1, 4, 8, 11, 13, 15, 28 and 42 days. Silage pH and carbohydrate levels declined more rapidly in sulla than pasture silage, while lactic acid content increased more rapidly. Silage ammonia levels increased rapidly in pasture silage but remained low in sulla silage. In Experiment 3, sulla and pasture mixtures as used in Experiment 1 were ensiled at three moisture levels, in a 5*3 factorial design. Final pH was lower (P<0.001) 17 days after ensiling with increasing moisture content and by increasing the proportion of sulla in the silage (P<0.0001). High moisture silage or silage with a high proportion of sulla, had the highest lactic acid and soluble carbohydrate contents. These studies suggest that sulla has the potential to be used to produce high quality silage. Sulla silage needs to be evaluated in feeding trials to determine if its potential as a high quality supplementary feed can be realised as animal performance. Keywords: ammonia, condensed tannins, Hedysarum coronarium, lactic acid, pasture, pH, silage, sulla