A. Machmüller

Supplementation of Acacia mearnsii tannins decreases methanogenesis and urinary nitrogen in forage-fed sheep

The objective of this experiment was to assess the effects of a partial replacement of ryegrass (Lolium perenne) by red clover (Trifolium pratense) or alfalfa (Medicago sativa) supplemented with 0 or 41 g Acacia mearnsii extract (containing 0.615 g/g condensed tannins)/kg dietary dry matter on nitrogen turnover and methane release by sheep, using the respiration chamber technique. Across all variables, there was no significant interaction between basal diet and tannin supplementation. The partial replacement of the grass by the legumes remained without effect on the amounts of nitrogen excreted through faeces or urine. Nitrogen and energy utilisation was lower (P < 0.05) with ryegrass-alfalfa than with ryegrass alone, and methane release (kJ/MJ gross energy intake) was higher (P < 0.05) with ryegrass-red clover than with ryegrass alone. Tannin supplementation decreased (P < 0.05) ruminal ammonia concentration and urinary nitrogen excretion without affecting body nitrogen and energy retention, and reduced (P < 0.001) methane release by 13% on average. The results suggest that supplemented Acacia mearnsii tannins can be useful in mitigating methane and potential gaseous nitrogen emissions, whereas a replacement of grass by legumes obviously shows no advantage in this respect.

Methane suppression by coconut oil and associated effects on nutrient and energy balance in sheep

Three different diets with increasing proportions of coconut oil (0, 3.5 and 7%) were fed to six sheep in an incomplete Latin square experiment with four replicates per diet. The diets were composed of hay and concentrates either without or with coconut oil. Concentrate comprised 28.8 and 54.6% of the diet DM in the treatments containing 3.5 and 7% coconut oil, respectively. Wethers on all treatments were fed at 1.2 × maintenance. Gaseous exchange was measured in respiratory chambers. Protozoa counts were reduced (P < 0.05) by 88 and 97% when diets contained 3.5 and 7% coconut oil, respectively, whereas bacteria counts increased (P < 0.05). Supplementation of coconut oil at proportions of 3.5 and 7% suppressed (P < 0.001) methane production by 28 and 73%, respectively, as related to the unsupplemented diet. This proportionately reduced (P < 0.001) the amount of gross energy lost through methane from 7.5 to 5.7 and 2.5%, in diets containing 0, 3.5 and 7% coconut oil, respectively. Assuming a linear suppres...

Ruminal methanogenesis as influenced by individual fatty acids supplemented to complete ruminant diets

F. DOHME, A. MACHMÜLLER, A. WASSERFALLEN AND M. KREUZER. 2001. The objective of the present study was to investigate the effects of seven different pure fatty acids on rumen fermentation using the rumen simulation technique (RUSITEC). The fatty acids were supplied to a complete ruminant diet at a proportion of 50 g kg−1 dietary dry matter and compared with an unsupplemented control. Methane release and methanogenic counts were suppressed by the fatty acids C12 : 0, C14 : 0 and C18 : 2 whereas C8 : 0, C10 : 0, C16 : 0 and C18 : 0 showed no corresponding effects. Apart from C12 : 0 and C18 : 2, C8 : 0 and C10 : 0 also adversely affected ciliate protozoa suggesting independence from the methane‐suppressing effect of medium‐chain fatty acids (MCFA). Although MCFA but not C18 : 2 reduced ruminal fibre degradation, the influence on other fermentation traits remained low. In conclusion, the supply of certain fatty acids to ruminant diets seems to have the potential to reduce methane release.

Comparative evaluation of the effects of coconut oil, oilseeds and crystalline fat on methane release, digestion and energy balance in lambs.

The effects of coconut oil, crushed whole oilseeds (rapeseed, sunflower seed and linseed) and rumen-protected crystalline fat on methane release, digestion and energy balance in growing lambs were evaluated in relation to an unsupplemented control diet. The diets consisted of maize silage, grass hay and concentrate which was supplemented with the respective lipid source. On average, the five lipid-supplemented diets contained 56 g ether extract per kg dry matter, whereas the unsupplemented control diet had 31 g kg ˇ1 dry matter The experiment was carried out with 12 lambs in an incomplete 66 Latin square with each lamb being fed, subsequently, three different diets for 3 weeks. Feed was allocated according to calculated requirements of metabolizable protein and energy. Gaseous exchange was measured in open-circuit respiratory chambers. Coconut oil supplementation reduced (p<0.1) methane release per kg live weight by 26% compared to control, and with the use of rapeseed, sunflower seed and linseed the relative reduction was 19%, 27% and 10%, respectively. The effects of the lipid supplementations on methane release were significant when related to gross energy intake (p<0.05), CO2 release (p<0.05) and total energy loss (p<0.01). A persistence of the methane suppression seems to be given at least partially. Supplementing the oilseeds, particularly sunflower seed, reduced (p<0.05) the apparent digestibilities of NDF and ADF. This suggests that the reduced fermentation of fiber was also important for the methane suppression by oilseeds whereas with coconut oil treatment the direct inhibitory effects on rumen methanogens might have been predominant. Lipid supplementation, except of rumen-protected fat, reduced rumen fluid ciliate count (p<0.1) and total VFA concentration (p<0.05), and depressed the concentration of acetate (p<0.05) and butyrate (p<0.001). This diminished (p<0.05) the ratio of acetate to propionate. The apparent digestibilities of individual fatty acids were relatively high in all

Potential of various fatty feeds to reduce methane release from rumen fermentation in vitro (Rusitec)

The effects of coconut oil and whole crushed oilseeds (rapeseed, sunflower seed and linseed) on rumen fermentation, as well as on methane and hydrogen release, were evaluated in vitro employing the rumen simulation technique (Rusitec). A low-fat diet served as the negative control and a diet with rumen protected fat as the positive control. By using two different proportions of concentrate in the diet, 6% and 9% of total lipids were supplied with each of the five fat supplemented diets, whereas the control diets contained about 3% total lipids. The 12 diets were provided at daily amounts of 11 g and 22 g dry matter. Rumen-protected fat as well as rapeseed had small effects on fermentation pattern and methane formation, which presumably resulted from the exchange of carbohydrates by fat. In contrast, coconut oil, sunflower seed and linseed significantly reduced protozoa count and methane release. An increased fat supply by the higher concentrate proportion further supported the suppressing effects of these types of fat on protozoa and methane. Coconut oil completely eliminated protozoa from rumen fluid after four to nine days of application, and this period was shorter by more than 30% on average at the higher level of supply. As compared with the low-fat treatment, coconut oil suppressed methane by 43% with medium and 57% with high concentrate level. The maximum methane reduction with sunflower seed and linseed accounted for about 40%. An increase in hydrogen release was found with coconut oil and oilseeds which, however, was considerably lower than the hydrogen quantities that were less incorporated into methane. In these situations, hydrogen recovery, as calculated from hydrogen balance, was reduced.

Efficacy of plant extracts rich in secondary constituents to modify rumen fermentation

Three plant extracts with different secondary constituents were simultaneously evaluated in an eight fermenter rumen simulation technique (Rusitec) for their effects on ruminal fermentation pattern. Specifically, a Yucca schidigera extract containing the saponin compound sarsaponin was supplied at three concentrations (1, 20 and 100 mg sarsaponin/kg dry matter (DM)) and was compared to a Castanea sativa wood extract containing hydrolysable tannins (0.5 and 2.5 g tannins/kg) and pure sulphonate-free lignin (2.5 g/kg). The supplements were added to a basal diet (grass silage, barley grain, grass hay) with a low crude protein (CP) content. These diets were compared to the same, unsuppplemented basal diet (control) and to a diet with additional soybean meal providing protein according to recommendations for dairy cow diets. The control diet and the soybean meal diet differed in rumen fluid ammonia concentration by 15% (13.6 mmol/l versus 16.0 mmol/l). Relative to the control diet, the high doses of the saponin-rich and the tannin-rich extract reduced the rumen fluid ammonia level by up to 21%. There was a tendency for elevated levels of apparent protein degradation during 48 h of fermentation, suggesting that the effect of the extracts on ammonia probably did not result from suppression of microbial protein degradation. Bacterial and protozoal counts in rumen fluid were not influenced by dietary treatments. Substantive effects of the saponin-rich and tannin-rich products on ruminal nitrogen metabolism were observed only at doses exceeding those recommended by the manufacturers.

The role of the rumen ciliate protozoa for methane suppression caused by coconut oil

Diets containing either coconut oil or rumen‐protected fat (54 g kg−1 dry matter each) were supplied to Rumen Simulation Technique fermenters filled with faunated and defaunated rumen fluid in a 2 × 2 factorial design. Defaunation immediately reduced methane formation by about 40% with each diet. With coconut oil, methane gradually declined in faunated and defaunated rumen fluid. Finally, the extent of methane suppression was similar, both with coconut oil and with defaunation. Independently of the status of protozoa, the population of methanogens in rumen fluid was significantly reduced by coconut oil. The results suggest that defaunation and coconut oil independently and additively suppress rumen methanogenesis.

Methane-suppressing effect of myristic acid in sheep as affected by dietary calcium and forage proportion.

The efficiency of myristic acid (14 : 0) as a feed additive to suppress CH4 emissions of ruminants was evaluated under different dietary conditions. Six sheep were subjected to a 6 x 6 Latin square arrangement. A supplement of non-esterified 14 : 0 (50 g/kg DM) was added to two basal diets differing in their forage:concentrate values (1 : 1.5 and 1 : 0.5), which were adjusted to dietary Ca contents of 4.2 and 9.0 g/kg DM, respectively. Comparisons were made with the unsupplemented basal diets (4.2 g Ca/kg DM). The 14 : 0 supplementation decreased (P<0.001) total tract CH4 release depending on basal diet type (interaction, P<0.001) and dietary Ca level (P<0.05, post hoc test). In the concentrate-based diet, 14 : 0 suppressed CH4 emission by 58 and 47 % with 4.2 and 9.0 g Ca/kg DM, respectively. The 14 : 0 effect was lower (22 %) in the forage-based diet and became insignificant with additional Ca. Myristic acid inhibited (P<0.05) rumen archaea without significantly altering proportions of individual methanogen orders. Ciliate protozoa concentration was decreased (P<0.05, post hoc test) by 14 : 0 only in combination with 9.0 g Ca/kg DM. Rumen fluid NH3 concentration and acetate:propionate were decreased (P<0.05) and water consumption was lower (P<0.01) with 14 : 0. The use of 14 : 0 had no clear effects on total tract organic matter and fibre digestion; this further illustrates that the suppressed methanogenesis resulted from direct effects against methanogens. The present study demonstrated that 14 : 0 is a potent CH4 inhibitor but, to be effective in CH4 mitigation feeding strategies, interactions with other diet ingredients have to be considered.

Comparative efficiency of various fats rich in medium-chain fatty acids to suppress ruminal methanogenesis as measured with RUSITEC.

A RUSITEC apparatus equipped with eight fermenters was used to investigate the effects of seven different fats with high proportions of medium-chain fatty acids (C8:0–C16:0) supplied at a level of 53 g kg−1 DM. In detail, coconut oil, palm kernel oil, palm oil, tallow, milk fat and two types of canola oils, both genetically enriched with lauric acid, were compared with a diet supplemented with prilled fat. The prilled fat was selected from three different rumen-protected fats in a preliminary experiment as the least effective one regarding methane release. Palm kernel oil, coconut oil and one of the canola oils significantly (P < 0.05) decreased methane release, methanogens and ciliates whereas the other fats had only minor effects. With the use of the three effective fats, NDF degradation was also suppressed (P < 0.05), but the rumen fluid concentration of volatile fatty acids remained unchanged. However, at constant acetate proportion, butyrate proportion increased (P < 0.05) at the expense of propionat...

Rumen Fermentation and Nitrogen Balance of Lambs fed Diets Containing Plant Extracts Rich in Tannins and Saponins, and Associated Emissions of Nitrogen and Methane

Tannins were added to experimental diets at levels of 1 and 2g/kg DM (hydrolysable tannins; Castanea sativa wood extract) and saponins at 2 and 30mg/kg DM (sarsaponin; Yucca schidigera extract). These levels were far below thresholds expected to be adverse in ruminants. Effects were measured in lambs by comparison with unsupplemented control diets calculated to be either deficient (10%) or adequate in protein. The diets consisted of hay, concentrate (1:1) and extra wheat starch with increasing body weight. Ruminal pH, VFA concentration, protozoa count and apparent digestibilities of organic matter and fibre did not differ among treatments. The low tannin dose significantly decreased bacteria count compared to the high saponin dose. Saponin supplementation and the high tannin dose showed some potential to reduce ruminal ammonia concentration. This was associated with weak trends towards lower urine N excretion (only tannins) and ammonia emission from manure. Methane release was increased by the low tannin dose compared to the unsupplemented control. Diet effects on heat production were not systematic. In conclusion, the extracts rich in tannins or saponins gave only slight indications for either increased body nitrogen retention or reduced nitrogen emission. However, effects might have been larger with more pronounced dietary protein deficit.