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

The aim of this work was to investigate the effect of a-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 200 mg 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 48 h 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 200 mg of active component/L culture medium and bromochloromethane (BCM) at a concentration of 10 mg/L culture medium against three different archaeal strains: Methanobrevibacter ruminantium, Methanobrevibacter smithii and Methanobrevibacter millerae. In vivo, no significant (P