Abstract:
Natural compounds such as plant secondary metabolites (PSM) can be used to replace
antibiotic growth promoters as rumen modifiers. In this study, the effectiveness of stored and freshly
extracted Aloe vera (AV), Azadirachta indica (AZ), Moringa oleifera (MO), Jatropha curcas (JA), Tithonia
diversifolia (TD) and Carica papaya (CP) crude extract and monensin on in vitro gas and methane
production, organic matter digestibility (IVOMD) and volatile fatty acids (VFA) were evaluated using
a total mixed ration (TMR), lucerne or Eragrostis curvula substrates. Fresh extracts were processed
from the same batch of frozen (20 C) plant material a few days before the trial while the stored
extracts were extracted and stored at 4 C for 12 months prior to the study. Extraction was done by
solubilising 50 g freeze-dried plant material in 500 mL 100% methanol. Four mL of reconstituted
50 mg crude extract per 1000 mL distilled water was added per incubation vial, which already
contained 400 mg substrate and in vitro fermentation, and gas production and IVOMD evaluation
were carried out using standard procedures. Results showed that storing plant extracts for 12 months
did not affect the activity or stability of metabolites present in the crude extracts, as shown by the
lack of differences in total gas production (TGP) and methane produced between fresh or stored
extracts across the substrates. In the TMR substrate, plant extracts increased IVOMD but did not a ect
TGP and methane production, whereas monensin did not have any effect. Plant extracts increased
IVOMD of Eragrostis substrate and supressed methane production to a greater extent than monensin
(p < 0.05). It can be concluded that storing plant extracts for up to 12 months did not compromise
their efficacy. In addition, the use of 50 mg/kg of AV, AZ, MO, JA, TD and CP extract to a forage-based
diet will reduce methane production while improving feed digestibility.
