O-acetylation of cell wall polysaccharides and other factors affecting the digestibility of fescue tussock : A thesis submitted to fulfil the requirements for the degree of Master of Science in the University of Canterbury [Lincoln College]

Abstract

A great deal of research has been done aimed at improving the efficiency of farming ruminant animals in New Zealand and throughout the world. Considerable results have been achieved in the field of animal breeding and also in the improvement of pasture quality. Much of the research has been directed towards understanding the factors which determine pasture quality. The digestibility of pasture species is one of the main criteria for their evaluation as forages and considerable effort has been devoted to discovering how the chemical composition of a plant affects its digestion by ruminants. The picture being built up by this work is by no means complete and research is continuing.

The tussock grasslands occupy a large area of New Zealand, especially in the South Island where brown tussock grassland occurs in wide areas east of the divide; extending in- places from sea level to an altitude of 1500m. Festuca novae zealandiae is the dominant species in much of this short tussock grassland. Festuca mathewsii has quite a widespread distribution in the southern half of the South Island. Plants of these species are composed of closely bunched needle like leaves with slender stems. Notable features are their low moisture content and tough fibrous nature. The tussock grasses in general are very low quality forages which are only eaten by sheep and cattle in adverse conditions when there is very little else to eat. Nevertheless the great quantity of tussock growing in New Zealand makes it an important resource.

This study is aimed at investigating the effect of O-acetylation of cell wall polymers on digestibility and at determining the importance of O-acetylation and other factors which affect digestibility in the evaluation of fescue tussocks. The relationship between O-acetyl content, lignin content and cell wall digestibility are examined for three Festuca species. The effects of varying growth conditions on the acetyl content and lignin content of Festuca novae zealandiae plants are also investigated.