Resumo

RAMIREZ-ORDUNA, Rafael et al. Seasonal dynamics of ruminal crude protein digestion of browse species from baja california sur, mexico. INCI [online]. 2003, vol.28, n.7, pp.408-414. ISSN 0378-1844.

Ten native browse species from Baja California Sur, Mexico, were nutritionally evaluated in each season of three consecutive years measuring crude protein (CP), protein fraction in neutral detergent fiber (NDIP) and in acid detergent fiber (ADIP), and rate and extent of crude protein degradability. Five legumes and five non-legumes were collected from 16 linear 30m transects. All plants in each transect were identified and measured to estimate Shannon’s diversity index, species richness, aerial cover and relative frequency, dominance, density and importance. Medicago sativa L. hay was used as reference forage with high nutritional quality. To estimate the effective degradability of crude protein (EDCP), duplicate nylon bags (10x15cm; 50µm pore size) containing 4g of each plant species from each season and year were incubated in the ventral part of the rumen in four cannulated beef steers. In general, CP content, NDIP, ADIP and EDCP were significantly higher in legumes. Neutral detergent soluble CP was higher in non-legumes during spring and summer, and CP and EDCP were higher in autumn. Legume EDCP was significantly lower in summer, possibly due to reduction of available cell wall protein. Only shrubs such as Opuntia cholla, Prosopis sp. and Cercidium floridium had EDCP values comparable to or higher than alfalfa hay. Cyrtocarpa edulis had the lowest EDCP. Legume CP was more degraded in the rumen than that of non-legumes. A high quality forage period in autumn and winter, and a low quality one in spring and summer, could be distinguished.

Palavras-chave : Native Shrubs; Sonora Desert; Crude Protein; Cell Wall Proteins; Degradability of Crude Protein.