The effect of Helinus integrifolius (Lam.) kutze crude leaf extract on ruminant gas production and fodder digestibility

Thesis (M.Sc. (Botany)) -- University of Limpopo, 2017

There have been numerous attempts to alleviate enteric methane emissions by ruminants in both commercial and subsistence farming. This is because methane is the most potent greenhouse gas responsible for atmospheric contamination leading to the greenhouse effect, global warming and climate change. Although, carbon dioxide emissions via the use of fossil fuels and in industrial production have had considerable attention, livestock production continues to contribute substantial amounts (80 Mt per year) of methane to the atmosphere. Ruminants are a source of meat and dairy products that mankind cannot do without. Eliminating them is definitely not a viable option hence strategies such as feed, feeding management and nutrition, rumen modifiers and animal genetic production and other management approaches have been proposed. Recently studies have focused on the use of plants with high content of secondary metabolites. Plant secondary metabolites possess numerous desirable biological activities which lead to their exploitation as nutraceuticals, pharmaceuticals/recreational drugs and supplements. Properties such as antifungal, antimicrobial and anti-inflammatory effects have prompted their use in attempts to reduce enteric fermentation’s major by-product i.e. methane. This study’s main objective was to investigate the effect of a methanolic crude saponin extract and leaf powder of Helinus integrifolius on in vitro ruminant total gas production and fodder digestibility. A methanolic crude extract was obtained by sequential extraction in Soxhlet apparatus starting with n-hexane and then methanol. Total gas production and feed digestibility were quantified using a ruminant gas production/digestion bioassay. The gas released was analysed with the aid of gas chromatography. The methanolic crude extract was found to contain 286.0±0.60 mg saponins/g of dry material by colorimetric spectrophotometry. In numerous studies the anti-methanogenic effect in ruminants is attributed to condensed tannin activity. However, no tannins were detected in the methanolic crude saponin extract when a tannin test was performed. The methanolic crude saponin extract showed substantial reduction of total gas release (99%) and increased fodder digestion (55%) compared to the control treatment. Leaf powder inclusion did not reduce total gas release. However, digestion was slightly improved but less than 50% of dry material was digested. It was evident that leaf powder inclusion had minimum effect on ruminant enteric microbial activity. The methanolic crude saponin extract imposed much vi greater effects in both total gas production and fodder digestibility compared to the leaf powder. These observations indicate that the Helinus integrifolius plant may be one of the ideal candidates with potential to reduce ruminant methane production. Furthermore, its methanolic crude saponin extract may contain the ideal phytochemicals to be investigated further as a ruminant feed additives/supplement. They may aid in the alleviation of enteric fermentation and increased feed utilisation efficiency while improving dairy and meat yield in livestock production.