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

Papaya leaf methanolic extract (PLE) at concentrations of 0 (CON), 5 (LLE), 10 (MLE) and 15 (HLE) mg/250mg dry matter (DM) with 30mL buffered rumen fluid were incubated for 24h to identify its effect on in vitro ruminal methanogenesis and ruminal biohydrogenation (BH). Total gas production was not affected (P>0.05) by addition of PLE compared to the CON at 24h of incubation. Methane (CH4) production (mL/250mg DM) decreased (P<0.05) with increasing levels of PLE. Acetate to propionate ratio was lower (P <0.05) in MLE (2.02) and HLE (1.93) compared to the CON (2.28). Supplementation of the diet with PLE significantly (P <0.05) decreased the rate of BH of C18:1n-9 (oleic acid; OA), C18:2n-6 (linoleic acid; LA), C18:3n-3 (linolenic acid; LNA) and C18 polyunsaturated fatty acids (PUFA) compared to CON after 24h incubation, which resulted in higher concentrations of BH intermediates such as C18:1t11 (vaccenic acid; VA), c9t11 conjugated LA (CLA) (rumenic acid; RA) and t10c12 CLA. Real-time PCR analysis indicated that the total bacteria, total protozoa, Butyrivibrio fibrisolvens and methanogen population in HLE decreased (P <0.05) compared to CON, but the total bacteria and B. fibrisolvens population were higher (P<0.05) in CON compared to the PLE treatment groups.