In Vitro Fermentation of Browsable Native Shrubs in New Zealand

Area of Science:

• Ruminant nutrition
• Forage evaluation
• In vitro fermentation studies

Background:

• Limited data exists on the nutritive value of native New Zealand shrubs for livestock.
• Native shrubs have potential as sustainable fodder, mitigating environmental impacts on farms.
• Exotic fodder species are commonly used, but native alternatives warrant investigation.

Purpose of the Study:

• To measure in vitro fermentation gas production of native shrubs.
• To predict fermentation kinetics and estimate volatile fatty acids (VFA), microbial biomass (MBM), and greenhouse gas production.
• To compare native shrubs with an exotic fodder species, Salix schwerinii.

Main Methods:

• In vitro fermentation assays were conducted on four native shrubs and S. schwerinii.
• Single-pool and dual-pool models were used to predict fermentation kinetics.
• Measurements included total gas production, VFA, MBM, and greenhouse gases.

Main Results:

• Native shrubs exhibited higher total in vitro gas production than S. schwerinii.
• The dual-pool model provided a more accurate prediction of fermentation kinetics.
• Native shrubs yielded higher VFA and greenhouse gas production but lower MBM compared to S. schwerinii.

Conclusions:

• Native shrubs can supply adequate energy and microbial protein for ruminant livestock.
• Greenhouse gas production from native shrubs falls within expected ranges for New Zealand pastures.
• Further research is needed to explore the role of condensed tannins in S. schwerinii's fermentation characteristics.