<i>In-Vitro </i>Fermentation of Browsable Native Shrubs in New Zealand

Information on the nutritive value and in vitro fermentation characteristics of native shrubs in New Zealand is scant. This is despite their potential as alternatives to exotic trees and shrubs for sup-plementary fodder, and mitigation of greenhouse gas and soil erosion on hill country sheep and beef farms. The objectives of this study were to measure the in vitro fermentation gas production, predict parameters of in vitro fermentation kinetics and to estimate in vitro fermentation of volatile fatty acids (VFA), microbial biomass (MBM) and greenhouse gases of four native shrubs (Coprosma robusta, Griselinia littoralis, Hoheria populnea and Pittosporum crassifolium) and an exotic fodder tree species, Salix schwerinii. Total in vitro gas production was higher (p<0.05) for natives than S. schwerinii. Prediction using the single pool model resulted in biologically incorrect negative in vitro total gas production from the immediately soluble fraction of the native shrubs. However, the dual pool model better predicted in vitro total gas production and was in alignment with measured in vitro fermentation end products. In vitro VFA and greenhouse gas production from fermentation of leaf and stem material were higher (p<0.05), and MBM lower (p<0.05), for native shrubs com-pared to S. schwerinii. The lower in vitro total gas production, VFA and greenhouse gases produc-tion, and higher MBM of S. schwerinii may be explained by the presence of condensed tannins (CT), although this was not measured and requires further study. In conclusion, results from this study suggests that when consumed by ruminant livestock, the browsable native shrubs can provide adequate energy and microbial protein, and that greenhouse gas production from these species is within ranges reported for typical New Zealand pastures.