Investigating unsaturated fat, monensin, or bromoethanesulfonate in continuous cultures retaining ruminal protozoa. I. Fermentation, biohydrogenation, and microbial protein synthesis

Abstract

Methane is an end product of ruminal fermentation that is energetically wasteful and contributes to global climate change. Bromoethanesulfonate, animal-vegetable fat, and monensin were compared with a control treatment to suppress different functional groups of ruminal prokaryotes in the presence or absence of protozoa to evaluate changes in fermentation, digestibility, and microbial N outflow. Four dual-flow continuous culture fermenter systems were used in 4 periods in a 4 x 4 Latin square design split into 2 subperiods. In subperiod 1, a multistage filter system (50-microm smallest pore size) retained most protozoa. At the start of subperiod 2, conventional filters (300-microm pore size) were substituted to efflux protozoa via filtrate pumps over 3 d; after a further 7 d of adaptation, the fermenters were sampled for 3 d. Treatments were retained during both subperiods. Flow of total N and digestibilities of NDF and OM were 18, 16, and 9% higher, respectively, for the defaunated subperiod but were not different among treatments. Ammonia concentration was 33% higher in the faunated fermenters but was not affected by treatment. Defaunation increased the flow of nonammonia N and bacterial N from the fermenters. Protozoal counts were not different among treatments, but bromoethanesulfonate increased the generation time from 43.2 to 55.6 h. Methanogenesis was unaffected by defaunation but tended to be increased by unsaturated fat. Defaunation did not affect total volatile fatty acid production but decreased the acetate:propionate ratio; monensin increased production of isovalerate and valerate. Biohydrogenation of unsaturated fatty acids was impaired in the defaunated fermenters because effluent flows of oleic, linoleic, and linolenic acids were 60, 77, and 69% higher, and the ratio of vaccenic acid:unsaturated FA ratio was decreased by 34% in the effluent. This ratio was increased in both subperiods with the added fat diet, indicating an accumulation of intermediates of biohydrogenation. However, the flow of 18:2 conjugated linoleic acid was unaffected by defaunation or by treatments other than added fat. The flows of trans-10, trans-11, and total trans-18:1 fatty acids were not affected by monensin or faunation status.

Relationships between ruminal Gram-positive bacteria and methane from lactating dairy cows supplemented with monensin and tallow, alone or in combination

“…The molar ratios of acetic acid, propionic acid, and butyric acid, as well as the acetate:propionate ratio were not different between the control and treatment groups. Similar to this study, some studies have not shown a difference in the molar ratio of these parameters between animals fed monensin and tallow (18,19). Tallow supplementation provides unsaturated fatty acids that can serve as electron acceptors during biohydrogenation in the rumen, and this reaction will reduce the amount of H + available to reduce CO 2 (32).…”

“…Tallow supplementation, on the other hand, can increase the energy density in the diet, thus increasing milk production Relationships between ruminal Gram-positive bacteria and methane from lactating dairy cows supplemented with monensin and tallow, alone or in combination and metabolic efficiency (14). Moreover, it reduces the amount of fermentable matter, which reduces methane production (25), and increases the unsaturated fatty acid content, which has a toxic effect on methanogens and Gram-positive bacteria (19). Beauchemin et al (4) have shown that 14% less methane was emitted from cows fed a diet supplemented with tallow, compared with a control diet.…”

Effects of supplementing a mixed diet with echium (<i>Echium plantagineum</i>) oil on methanogenesis in a rumen simulation system

“…In the present study, the effects of echium oil supplementation on methanogenesis were evaluated in RUSITEC, in comparison to those of positive (basal diet) and negative (BES) controls. Methane production was only detected on day 3 of the experimental period for the BES treatment (data not shown), as earlier observed by Karnati et al (2009) with 250 µM of BES, and suggesting an adaptation of the methanogenic population to the halogenated compound. Sodium 2-bromoethanesulfonate reduced methane production by 92.8%, compared to the control, a similar finding (95%) being described for the same supplementation level in vitro (Lee et al, 2009).…”

Strategies for optimizing nitrogen use by ruminants

“…The quantitative importance of this process in current feeding practices needs to be evaluated. Defaunation usually results in an increase in the EMPS due to lower internal recycling of N. Karnati et al (2009) reported in a dual flow continuous culture study designed to specifically retain protozoa in the vessel that defaunation resulted in an increased efficiency of N utilization by bacteria (95.6% v. 75.4%), but when ENU-R was calculated considering the microbial (bacteria and protozoa) protein synthesis, the differences were much smaller (90.8% v. 95.7%). The impact of protozoa on the ENU-R requires further research.…”