Tropical fruit peels as potential modifiers of rumen fermentation characteristics in goats: in vitro and in situ evaluations

Abstract

Context Methane (CH4) accounts for loss of dietary gross energy in ruminants and is a potent greenhouse gas. Feedstuffs that could alter ruminal fermentation by decreasing methane production without reducing total volatile fatty acid (VFA) concentration are desirable. Aims Tropical fruit peels, which can be simply collected and exploited, were compared with lucerne (Medicago sativa) in order to assess their potential to modify in vitro and in situ rumen fermentation and CH4 production of goats. Methods For the in vitro study, buffered rumen fluid (30 mL from each of four rumen-fistulated goats fed concentrate and lucerne hay) was mixed with 250 mg dry matter (DM) of each peel sample (dokong, mangosteen, papaya, pineapple, rambutan) and incubated for 48 h. A total of 250 mg DM of lucerne was mixed with rumen fluid as control. For the in situ study, dried samples (lucerne, and peel of dokong, mangosteen, papaya, pineapple, rambutan) were passed through a 2-mm sieve, weighed (5 g) into nylon bags, and individually placed in the rumen of four fistulated goats for 48 h. Key results In the in vitro study, tropical fruit peels lowered (P < 0.05) the production of CH4 compared with lucerne. Tropical fruit peels did not cause inhibition of total VFA (e.g. acetic, butyric and propionic acids) or decrease the concentration of ammonia-N compared with lucerne. In the in situ study, effective DM degradability of papaya (62.99%) and pineapple (54.45%) peels were higher than of lucerne (51.04%). Potential DM degradability of pineapple (75.07%), dokong (72.62%), papaya (66.88%) and rambutan (59.15%) were also higher than of lucerne (57.55%). Conclusions Tropical fruit peels had no negative effect on ruminal fermentation and reduced CH4 production in vitro. However, in vivo studies should confirm these effects. Implications Tropical fruit peels may be suitable as a feedstuff for goats and could be an effective way to reduce methane gas emissions; however, more research under in vivo conditions is needed to elucidate the mechanisms by which tropical fruit peels mitigate of methane production in ruminants.