Dietary supplemental plant oils reduce methanogenesis from anaerobic microbial fermentation in the rumen.

Ruminants contribute to the emissions of greenhouse gases, in particular methane, due to the microbial anaerobic fermentation of feed in the rumen. The rumen simulation technique was used to investigate the effects of the addition of different supplemental plant oils to a high concentrate diet on ruminal fermentation and microbial community composition. The control (CTR) diet was a high-concentrate total mixed ration with no supplemental oil. The other experimental diets were supplemented with olive (OLV), sunflower (SFL) or linseed (LNS) oils at 6%. Rumen digesta was used to inoculate the fermenters, and four fermentation units were used per treatment. Fermentation end-products, extent of feed degradation and composition of the microbial community (qPCR) in digesta were determined. Compared with the CTR diet, the addition of plant oils had no significant (P > 0.05) effect on ruminal pH, substrate degradation, total volatile fatty acids or microbial protein synthesis. Gas production from the fermentation of starch or cellulose were decreased by oil supplementation. Methane production was reduced by 21-28% (P < 0.001), propionate production was increased (P < 0.01), and butyrate and ammonia outputs and the acetate to propionate ratio were decreased (P < 0.001) with oil-supplemented diets. Addition of 6% OLV and LNS reduced (P < 0.05) copy numbers of total bacteria relative to the control. In conclusion, the supplementation of ruminant diets with plant oils, in particular from sunflower or linseed, causes some favorable effects on the fermentation processes. The addition of vegetable oils to ruminant mixed rations will reduce methane production increasing the formation of propionic acid without affecting the digestion of feed in the rumen. Adding vegetable fats to ruminant diets seems to be a suitable approach to decrease methane emissions, a relevant cleaner effect that may contribute to alleviate the environmental impact of ruminant production.

Effect of Sunflower and Marine Oils on Ruminal Microbiota, In vitro Fermentation and Digesta Fatty Acid Profile.

This study using the rumen simulation technique (RUSITEC) investigated the changes in the ruminal microbiota and anaerobic fermentation in response to the addition of different lipid supplements to a ruminant diet. A basal diet with no oil added was the control, and the treatment diets were supplemented with sunflower oil (2%) only, or sunflower oil (2%) in combination with fish oil (1%) or algae oil (1%). Four fermentation units were used per treatment. RUSITEC fermenters were inoculated with rumen digesta. Substrate degradation, fermentation end-products (volatile fatty acids, lactate, gas, methane, and ammonia), and microbial protein synthesis were determined. Fatty acid profiles and microbial community composition were evaluated in digesta samples. Numbers of representative bacterial species and microbial groups were determined using qPCR. Microbial composition and diversity were based on T-RFLP spectra. The addition of oils had no effect on substrate degradation or microbial protein synthesis. Differences among diets in neutral detergent fiber degradation were not significant (P = 0.132), but the contrast comparing oil-supplemented diets with the control was significant (P = 0.039). Methane production was reduced (P < 0.05) with all oil supplements. Propionate production was increased when diets containing oil were fermented. Compared with the control, the addition of algae oil decreased the percentage C18:3 c9c12c15 in rumen digesta, and that of C18:2 c9t11 was increased when the control diet was supplemented with any oil. Marine oils decreased the hydrogenation of C18 unsaturated fatty acids. Microbial diversity was not affected by oil supplementation. Cluster analysis showed that diets with additional fish or algae oils formed a group separated from the sunflower oil diet. Supplementation with marine oils decreased the numbers of Butyrivibrio producers of stearic acid, and affected the numbers of protozoa, methanogens, Selenomonas ruminantium and Streptococcus bovis, but not total bacteria. In conclusion, there is a potential to manipulate the rumen fermentation and microbiota with the addition of sunflower, fish or algae oils to ruminant diets at appropriate concentrations. Specifically, supplementation of ruminant mixed rations with marine oils will reduce methane production, the acetate to propionate ratio and the fatty acid hydrogenation in the rumen.

Bacterial and protozoal communities and fatty acid profile in the rumen of sheep fed a diet containing added tannins.

This study evaluated the effects of tannins on ruminal biohydrogenation (BH) due to shifts in the ruminal microbial environment in sheep. Thirteen lambs (45 days of age) were assigned to two dietary treatments: seven lambs were fed a barley-based concentrate (control group) while the other six lambs received the same concentrate with supplemental quebracho tannins (9.57% of dry matter). At 122 days of age, the lambs were slaughtered, and the ruminal contents were subjected to fatty acid analysis and sampled to quantify populations of Butyrivibrio fibrisolvens, which converts C(18:2) c9-c12 (linoleic acid [LA]) to C(18:2) c9-t11 (rumenic acid [RA]) and then RA to C(18:1) t11 (vaccenic acid [VA]); we also sampled for Butyrivibrio proteoclasticus, which converts VA to C(18:0) (stearic acid [SA]). Tannins increased (P < 0.005) VA in the rumen compared to the tannin-free diet. The concentration of SA was not affected by tannins. The SA/VA ratio was lower (P < 0.005) for the tannin-fed lambs than for the controls, suggesting that the last step of the BH process was inhibited by tannins. The B. proteoclasticus population was lower (-30.6%; P < 0.1), and B. fibrisolvens and protozoan populations were higher (+107% and +56.1%, respectively; P < 0.05) in the rumen of lambs fed the tannin-supplemented diet than in controls. These results suggest that quebracho tannins altered BH by changing ruminal microbial populations.

A comparison of different legume seeds as protein supplement to optimise the use of low quality forages by ruminants.

The potential of different legume seeds species, including recently new developed varieties (Vicia faba: a commercial variety and varieties Alameda, Palacio and Baraka; Lupinus angustifolius; Pisum sativum and Cicer arietinum: varieties Fardon and Zegri) as protein supplements to low quality forages was evaluated. First, the chemical composition, in vitro digestibility, in situ degradability and in vitro/in situ intestinal digestibility of legume seeds were determined. The chemical composition was rather similar within genus. Vicia faba beans contained more condensed tannins (35.8-56.4 g/kg DM) and less ether extract (12.8-9.5 g/kg DM) than the other legumes. The rumen degradability and intestinal digestibility of the undegraded protein in the rumen was very similar among the seeds, with exception of lupins, having a much higher degradation rate than the rest. Second, the fermentation characteristics of diets, which were based on two low quality forages (olive leaves and barley straw) and feed blocks without or with supplementation of legume seeds or soybean meal, were investigated by using single-flow continuous culture fermenters. In this trial, the fermentation parameters (ammonia, pH and volatile fatty acids), the microbial protein synthesis and the degradation of olive leaves and barley straw promoted by the different diets were studied. Compared to soybean meal, beans and peas showed similar suitability as protein supplements for sustaining in vitro fermentation of low-quality forages. However, our results suggest a significant interaction between the type of legume used as supplement and the type of forage used, which need to be further studied in vivo.

The effect of absence of protozoa on rumen biohydrogenation and the fatty acid composition of lamb muscle.

The effects of the absence of protozoa in the rumen of lambs on animal growth, rumen fermentation, microbial diversity and fatty acid profiles in abomasal fluid and intramuscular fat were measured in ten control and ten protozoa-free (PF) lambs. PF lambs were prepared by isolating them from ewes within the first 24 h after birth. The PF and control lambs were kept for 4 months in two different fields and received a daily supplement of 250 g concentrate. The bacterial populations visualised by denaturing gradient gel electrophoresis differed between the two groups of animals and showed a higher bacterial diversity in control lambs than in PF lambs. Abomasal contents from control lambs contained higher concentrations of 22:5n-3 and 22:6n-3 and lower concentrations of vaccenic acid (trans-11-18: 1) and 20:3n-6 than PF lambs. The rest of the fatty acids, including the conjugated linoleic acid (CLA) isomers, were present at the same concentrations in abomasal contents from both experimental groups. Fatty acid composition in intramuscular fat showed differences between the groups. PF lambs had higher proportions of 18:0, 18:3, trans-10, cis-12-CLA and total SFA than control lambs. Control lambs had higher proportions of cis-9-18: 1, cis-9, cis-12-18:2, 20: 3n-6, 22:6n-3 (DHA) and MUFA. In conclusion, rumen defaunation led to higher tissue levels of the trans-10, cis-12-CLA isomer and SFA and lower PUFA:SFA ratio and n-3 PUFA in lamb muscle.