Browse species from Ethiopia: role in methane reduction and nematode control in goats

Abstract

SummaryThe aim of the research reported in this thesis was to evaluate browse species collected from Ethiopia for preference by goats, and for their in vitro anthelmintic and methane (CH 4 ) reduction properties. During the conduct of the studies observations were made warranting a further aim, to compare in vitro fermentation patterns of browse species using inocula from goats and cows kept on identical dietary regime.The preference of browse species using dry matter intake (DMI) as a proxy and in combination with polyethylene glycol (PEG), relationships between browse species intake and chemical composition were determined in Chapter 2. Air-dried leaves of Acacia etbaica, Cadaba farinosa, Capparis tomentosa, Dichrostachys cinerea, Dodonaea angustifolia, Euclea racemosa, Maerua angolensis, Maytenus senegalensis, Rhus natalensis and Senna singueana were used. Two cafeteria trials, each lasting 10 days were conducted using goats receiving a daily ration of grass hay and wheat bran, without (trial 1) or with (trial 2) the inclusion of PEG. Preference measured as the first 10 min browse DMI differed significantly among browse species and with PEG (P<0.0001). Browse with higher tannin content, D. cinerea, R. natalensis and A. etbaica were the most preferred species regardless of PEG presence. Preference appeared to be based on digestible fibre fraction, hemicellulose rather than tannin levels in the browse species.Extracts of the 10 browse species were evaluated for their anthelmintic activity against Haemonchus contortus (Chapter 3). The larval exsheathment inhibition assay (LEIA) was applied using H. contortus third stage larvae (L 3 ) in a dose dependent manner with extract concentrations of 0, 150, 300, 600, 1200 µg/ml phosphate buffered saline (PBS). The role of polyphenols in the inhibition against L 3 was evaluated using polyvinylpolypyrrolidone (PVPP). All browse extracts significantly (P<0.0001) inhibited larval exsheathment in a dose dependent manner with the dose required to inhibit 50% of the L 3 (EC 50 ) being highest in C. farinosa and lowest in E. racemosa and M. senegalensis. Polyvinylpolypyrrolidone treated A. etbaica, C. tomentosa, M. angolensis, R. natalensis and D. cinerea were different (P<0.001) from the control (only PBS), indicating that larval inhibition was largely due to non-phenolic compounds. Absence of significant differences between PVPP treated E. racemosa, M. senegalensis, D. angustifolia and S. singueana, and control suggest that inhibition was mostly attributable to tannins and other polyphenols. Browse species anthelmintic property against H. contortus L 3 was due to the presence of phenolic and non-phenolic compounds. 4In vitro gas production (GP), CH 4 , volatile fatty acids (VFA) and in vitro organic matter digestibility (IVOMD) of the 10 browse species were determined using PEG 6000 in Chapter 4. Proanthocyanidins (PA) were quantified using a modified HClbutanol method and PA composition was determined by UPLC-DAD, with detection of other polyphenols by UPLC-ESI-MS/MS. Subs...