High quality forages as supplements to low quality forages for ruminants. Effects on intake, digestibility and rumen digesta dynamics
Chapter 1: This chapter is a review of literature covering different aspects of ruminant forage nutrition. In this review, aspects of the rumen and its microbial environment and the nutrition requirements of rumen microbes, plant cell wall structure and its degradation by rumen microbes and the regulation of feed intake and digesta flow in ruminants are covered. The last part deals with supplementation of low quality forage diets, with emphasis on the use of high quality forages as supplements and their effect on food intake. Chapter 2: The first part of this chapter describes the experimental methods and analytical techniques used, and the source and analysis of forages used in this study. Natural pasture (veld) hay harvested in the dry season was used as the poor quality forage. Napier hay, harvested at 4 weeks growth during the wet season, and groundnut hay, harvested when the crop was mature, were used as the supplementary high quality forages. Veld hay had a low nitrogen and high NDF content (3.8 and 848 g/kg DM respectively), while napier hay and groundnut had high nitrogen and low NDF content (22.1, 21.0 and 700, 455 g/kg DM respectively). These differences in nutritive value indicated by chemical composition were confirmed by in sacco dry matter degradation and in vitro gas production tests. Groundnut hay, despite having a high solubility and high rate of degradation, had the least degradable cell walls due to lignification. Chapter 3: Expts 1 and 2. The objective of these experiments was to test the response in intake and digestibility, to supplementation of veld hay with different levels of napier or groundnut hays when the basal diet was not supplemented with urea. With both napier hay and groundnut hay, supplementation increased total feed intake (P < 0.05). There was a tendency for the intake of veld hay to be decreased by high levels of forage supplement.