Digestión ruminal de hierba verde y conservada de prados permanentes de montana

Abstract

The chemical composition and the rumen degradation characteristics of 30 forage samples from five plots of a permanent meadow have been determined. The forages were harvested either in June —primary growth— (20) or subsequently in September —Summer regrowth— (10). The samples from the June cut were preserved by different procedures: freeze drying —fresh forage— (5), sun curing —hay— (5), oven drying —dehydrated forage— (5) and ensiling in plástic bags —silage— (5). Herbage from the Summer regrowth were conserved either as fresh forage (5) or as hay (5). There were not differences in the chemical composition (g/kg DM) between fresh forage and hay, while silages had higher crude protein (131 vs. 121) and cell wall contents (533 vs. 470) than did fresh forages. Forages harvested in June had higher neutral detergent fiber (479 vs. 440) and lower crude protein (119 vs. 153) contents than those harvested in September. The protein degradation in the rumen of the dried forages (hay and dehydrated) was characterized by a lower solubility (39.2, 27.0 vs. 57.2 %), a faster degradation rate (0.215, 0.200 vs. 0.127h—l) and a longer lag time (5.3, 4.4 vs. 4.1 h) than the other preserved forages. The silage has the highest (82.0 %) and the dehydrated forage the lowest (68.2 %) valúes for the effective nitrogen degradability. The highest valúes for the cell wall degradability were observed in the sun cured forages (71.1 %). Forages harvested in June showed a slower rate and a lower potential degradability than those harvested in September.