W. K. Wang’s research while affiliated with China Agricultural University and other places

As a member of photosynthetic bacteria, Rhodopseudomonas palustris, which has extraordinary metabolic versatility, has been applied as one of potential probiotics in feed industry. To explore whether R. palustris can increase rumen microbial viability and thus improve microbial fermentation, a 2 × 5 factorial experiment was conducted to evaluate the effect of R. palustris at dose rates of 0, 1.3, 2.6, 3.9, 5.2×10^6 CFU/mL on ruminal fermentation of two representative total mixed rations (HY, a ration for high-yield (>32 kg/d) lactating cows; LY, a ration for low-yield (<25 kg/d) lactating cows). After a 48 h in vitro rumen incubation, both rations resulted in different fermentation characteristics. The HY in comparison with LY group presented greater in vitro dry matter disappearance (IVDMD), cumulative gas production (GP48) and total volatile fatty acids (VFA, P<0.01). Increasing R. palustris addition linearly increased IVDMD (P<0.01) and GP48 (P<0.05), and the IVDMD increment in response to R. palustris addition was greater in LY than HY group (6.4% vs. 1.4%). Meanwhile, increasing R. palustris addition also linearly enhanced microbial protein synthesis and increased total VFA production (P<0.01), especially in LY group (up to 21.5% and 24.5% respectively). Unchanged acetate and declined propionate in molar percentage were observed in response to the R. palustris addition. Furthermore, increasing R. palustris addition altered fermentation gas composition in which molar O2 proportion in headspace of fermentation system was linearly reduced by 46.1% in LY and 32.9% in HY group, respectively (P<0.01), and methane production in both ration groups was enhanced by 1.9-4.1% (P=0.02). In summary, the R. palustris addition exhibited high potential for promoting the growth of rumen microorganism and enhancing microbial fermentation towards non-glucegenic energy supply by maintaining an anaerobic environment to microbe equilibrium.

Nitroethane (NE), 2-nitroethanol (NEOH) and 2-nitro-1-propanol (NPOH) were investigated in order to determine their inhibitory effects on in vitro ruminal fermentation and methane (CH 4 ) production of a hay-rich substrate (alfalfa hay: maize meal = 4:1, w/w). The rumen liquor collected from cannulated Holstein dairy cows was incubated at 39 °C for 72 h. The addition of NE, NEOH and NPOH slowed down the fermentation process and notably decreased molar CH 4 proportion by 96.8, 96.4 and 35.0%, respectively. The abundance of total methanogen and methanogens from the order Methanobacteriales were all decreased with NE, NEOH and NPOH supplementation. Meanwhile, the nitrocompound addition reduced mcr A gene expression, coenzyme F420 and F430 contents. The correlation analysis showed that CH 4 production was correlated positively with the population abundance of total methanogens, Methanobacteriales , mcr A gene expression, coenzyme contents of F420 and F430 . The nitrocompound addition decreased acetate concentration and increased propionate and butyrate concentrations in the culture fluid. In summary, both NE and NEOH addition presented nearly the same inhibitory effectiveness on in vitro CH 4 production; they were more effective than NPOH. The results of the current study provide evidence that NE, NEOH and NPOH can dramatically decrease methanogen population, mcr A gene expression and the coenzyme content of F420 and F430 in ruminal methanogenesis.