Chemical Features of Chionochloa Species in Relation to Grazing by Ruminants in South Island, New Zealand

Chionochloa species vary in the degree to which they are grazed by introduced ruminants. This is presumed to reflect the relative nutritive value and/or palatability of the forage provided by these indigenous grasses. Data are presented here on silicon content, in vitro organic matter digestibility (OMD), metabolisable energy (ME), crude protein and total nutrient mineral (TNM) contents of mature leaves of eleven Chionochloa species in southern New Zealand. Silification in all species is low, possibly as an evolutionary consequence of the absence of native mammalian herbivores in New Zealand. OMD determinations indicate a generally low nutritive value for these tussock grasses. Species characteristic of oligotrophic peats (c. acicularis and C. crassiuscula ssp. torta) produced very low values (20-25%) but others (C. pallens ssp. cadens, C. macra and C. ovata) approached OMD levels of medium quality pasture (50-60%). Crude protein values are also in the poor to moderate range (4.13% in C. acicularis to 8.34% in C. ovata). The values for total nutrient mineral content largely parallel those for protein. The results are discussed in relation to the apparent relative palatability of each species in the field, and the vulnerability to grazing of some species with restricted distributions.