Effects of propyl propane thiosulfinate on nutrient utilization, ruminal fermentation, microbial population and methane emissions in goats

Abstract

The aim of this work was to investigate the effect of α-cyclodextrin-propyl propane thiosulfinate complex (CD-PTS) as antimethanogenic compound in ruminants using in vivo and in vitro approaches. The in vivo trial lasted 36 days and was designed to study the effect of CD-PTS on ruminal methane production, fermentation pattern, microbial abundances and nutrient utilization in goats. Twelve adult goats fed with alfalfa hay and concentrate (50:50), were split in two groups: treated with CD-PTS complex at 200mg of active component/L rumen content per day or without any treatment (control). On days 7, 14, 21 and 28 methane emissions were recorded in chambers and rumen content samples were collected for pH, volatile fatty acid (VFA) and NH3 analyses. On day 14 and 28 rumen samples were collected for quantification of bacterial, protozoal and archaeal numbers by quantitative real-time PCR (qPCR) and to study the archaeal population structure by denaturing gradient gel electrophoresis. In addition, on days 17 and 18 samples of alfalfa hay were placed into nylon bags and incubated in the rumen of each goat for 24 and 48h to determine the ruminal degradation of dry matter (DM) and neutral detergent fiber (aNDFom). During the last 5 days of the trial, nutrient digestibility, N and energy balances and urinary purine derivative (PD) excretion were determined. Additionally, an in vitro experiment with pure cultures of methanogens was conducted to test propyl propane thiosulfinate (PTS) at a dose of 200mg of active component/L culture medium and bromochloromethane (BCM) at a concentration of 10mg/L culture medium against three different archaeal strains: Methanobrevibacter ruminantium, Methanobrevibacter smithii and Methanobrevibacter millerae. In vivo, no significant (P≤0.17) reduction on methane production was observed although a numerical decrease on day 28 was observed with CD-PTS. The dry matter intake (DMI), nutrient digestibility, N and energy balances, purine derivatives, creatinine and estimated microbial N flow were not affected by the treatment (P≤0.18). Likewise, total concentration of the analyzed microbial groups in the rumen, showed no difference (P≤0.33) between treated and non-treated goats. However, on day 28, the structure of the archaeal population in the rumen of goats treated with CD-PTS was different compared with that in control goats. The in vitro culture of methanogens showed a substantial reduction of methane production in all the strains by both BCM and PTS.