Effects of maturity on nutritive value of field-cured hays from common vetch and hairy vetch

Hay samples from common vetch and hairy vetch were collected at three maturity stages (bloom and two stages during pod-filling) with the aims of assessing the optimum harvesting stage and comparing the nutritive value of the two species. As maturation progressed, the hay content in cell wall increased and that of CP decreased. The two species showed different patterns in line with the maturing process, regarding digestibility of nutrients and effective degradability of DM and CP. Common vetch hay showed a progressive decrease of digestibility and degradability values in line with the maturing process of vegetative structures. Hairy vetch hay, however, showed a compensatory effect produced by an increasing grain proportion at later maturity stages. The nutritive value at flowering was higher for common vetch hay than for hairy vetch hay, but the opposite was observed at the stage of mature legumes. Voluntary DM intake was not affected by the species or harvest stages. Degradation studies, carried out by the nylon bag technique, showed that in these hays CP was extensively rumen degraded. Consequently, their digestible bypass protein should be low.