Protein, lignin and mineral contents and in situ dry matter digestibility of native Mexican grasses consumed by range goats

Native grasses from northeastern Mexico, such as Aristida spp., Bouteloua gracilis (Thurb), Cenchrus incertus (M.A. Curtis), Hilaria berlangeri (Steud. Nash), Panicum hallii (Varsey), Setaria macrostachya (H.B.K.), and Cenchrus ciliaris (L.), an introduced grass, that are consumed by range goats were evaluated to estimate seasonal CP, lignin, Ca, P, K, Mg, Na, Cu, Fe, Zn, Mn contents, and the rate and extent of DM digestion. The in situ nylon bag technique was used to estimate effective digestibility/degradability of DM (EDDM). Potential mineral intake by an adult range goat consuming these grasses was also estimated. The CP content in all grasses was significantly different between seasons. P. hallii had high annual mean CP contents (12%) and Aristida spp. (6%) was low. The native grasses B. gracilis (9%, annual mean), S. macrostachya (10%) and C. incertus (8%) had CP values comparable to the introduced grass C. ciliaris (9%). Lignin contents in all grasses were also significantly different between seasons. Aristida spp. had high annual means (10%) and H. berlangeri was low (6%). With the exception of H. berlangeri, all grasses had higher lignin contents (annual means) than C. ciliaris (6%). The EDDM in all grasses was significantly different between seasons. C. incertus (45%, annual mean) had the highest EDDM, while Aristida spp. (26%) was lowest. During spring and autumn, EDDM in all grasses was higher than in the other seasons. P. hallii, H. berlangeri and C. incertus had comparable EDDM values to C. ciliaris (40%) in all seasons. It was estimated that an adult range goat consuming the studied grasses, could eat sufficient amounts of Ca, Fe, and K (except for K from Aristida spp. in winter and summer), but of Na, Zn and Mn only in spring and autumn, and of Cu only in autumn. The P and Mg contents were marginally deficient in most grasses and in all seasons. The native grasses P. hallii, S. macrostachya, B. gracilis can be considered valuable grasses for goats on the range, because of their relatively high CP contents, and C. incertus, P. hallii and H. berlangeri because of their relatively high EDDM values, comparable to C. ciliaris. However, range goats consuming these grasses need to be supplemented with P and Mg in all seasons, with Na, Zn and Mn in winter and summer, and Cu in winter, spring and summer seasons.