Papaya (Carica papaya) leaf methanolic extract modulates in vitro rumen methanogenesis and rumen biohydrogenation

Area of Science:

• Ruminant nutrition and biochemistry
• Animal feed additives
• Greenhouse gas mitigation

Background:

• Ruminal methanogenesis contributes to greenhouse gas emissions.
• Dietary strategies are explored to mitigate methane production in livestock.
• Papaya leaf extract (PLE) is a potential feed additive.

Purpose of the Study:

• To evaluate the effects of papaya leaf methanolic extract (PLE) on in vitro ruminal methanogenesis.
• To assess the impact of PLE on ruminal biohydrogenation (BH) of fatty acids.
• To determine the influence of PLE on microbial populations in the rumen.

Main Methods:

• In vitro incubation of rumen fluid with varying concentrations of PLE (0, 5, 10, 15 mg/250 mg dry matter).
• Measurement of total gas production, methane (CH4) production, and volatile fatty acid profiles (acetate to propionate ratio).
• Analysis of fatty acid biohydrogenation intermediates and microbial populations (total bacteria, protozoa, Butyrivibrio fibrisolvens, methanogens) using real-time PCR.

Main Results:

• Methane production significantly decreased with increasing PLE levels.
• Acetate to propionate ratio was reduced at higher PLE concentrations.
• PLE supplementation decreased the biohydrogenation rate of C18 fatty acids, increasing BH intermediates like CLA and VA.
• Populations of total bacteria, protozoa, B. fibrisolvens, and methanogens were reduced by PLE, particularly at higher concentrations.

Conclusions:

• Papaya leaf extract (PLE) effectively suppresses in vitro ruminal methanogenesis.
• PLE alters ruminal fatty acid biohydrogenation, leading to increased beneficial fatty acid intermediates.
• PLE influences rumen microbial populations, potentially contributing to reduced methane emissions.