Michael Kreuzer

Nutritional management for enteric methane abatement: a review

A variety of nutritional management strategies that reduce enteric methane (CH4) production are discussed. Strategies such as increasing the level of grain in the diet, inclusion of lipids and supplementation with ionophores (>24 ppm) are most likely to be implemented by farmers because there is a high probability that they reduce CH4 emissions in addition to improving production efficiency. Improved pasture management, replacing grass silage with maize silage and using legumes hold some promise for CH4 mitigation but as yet their impact is not sufficiently documented. Several new strategies including dietary supplementation with saponins and tannins, selection of yeast cultures and use of fibre-digesting enzymes may mitigate CH4, but these still require extensive research. Most of the studies on reductions in CH4 from ruminants due to diet management are short-term and focussed only on changes in enteric emissions. Future research must examine long-term sustainability of reductions in CH4 production and impacts on the entire farm greenhouse gas budget.

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.

A study on the causes for the elevated n−3 fatty acids in cows' milk of alpine origin

The influence of grass-only diets either from rye-grass-dominated lowland pastures (400 m above sea level) or botanically diverse alpine pastures (2000 m) on the FA profile of milk was investigated using three groups of six Brown Swiss cows each. Two groups were fed grass-only on pasture (P) or freshly harvested in barn (B), both for two experimental periods in the lowlands and, consecutively, two periods on the alp. Group C served as the control, receiving a silage-concentrate diet and permanently staying in the lowlands. Effects of vegetation stage or pasture vs. barn feeding on milk fat composition were negligible. Compared with the control, α-linoleic acid (18∶3n−3) consumption was elevated in groups P and B (79%, P<0.001) during the lowland periods but decreased on the alp to the level of C owing to feed intake depression and lower 18∶3n−3 concentration in the alpine forage. Average 18∶3n−3 contents of milk fat were higher in groups, P and B than in C by 33% (P<0.01) at low and by 96% (P<0.001) at high altitude, indicating that 18∶3n−3 levels in milk were to some extent independent of 18∶3n−3 consumption. The cis-9,trans-11 CLA content in milk of grass-fed cows was higher compared with C but lower for the alpine vs. lowland periods whereas the trans-11, cis-13 isomer further increased with altitude. Long-chain n−3 FA and phytanic acid increased while arachidonic acid decreased with grass-only feeding, but none of them responded to altitude. Grass-only feeding increased milk α-tocopherol concentration by 86 and 134% at low and high altitude (P<0.001), respectively. Changes in the ruminal ecosystem due to energy shortage or specific secondary plant metabolites are discussed as possible causes for the high 18∶3n−3 concentrations in alpine milk.

Meat quality of Angus, Simmental, Charolais and Limousin steers compared at the same intramuscular fat content

Meat quality and marbling properties of Angus, Simmental, Charolais and Limousin steers (4×16) were compared at an average intramuscular fat content (IMF) of 3.25% in the M. longissimus dorsi. The steers were fattened on a forage-based diet until the desired, ultrasonically estimated IMF content was reached which resulted in considerably different growth and carcass characteristics. The Angus group showed a growth rate similar to Simmental and Charolais while Limousin grew slower, became oldest and provided the heaviest carcasses and best conformation. Angus carcasses showed the lowest weight but the highest fatness score. Marbling was equal for all breeds. Angus and Charolais provided pale meat with low haem iron content. Angus and Limousin beef was more tender on sensory assessment than Simmental beef, corresponding to differences found in shear force (non-significant) and myofibrillar fragmentation index measured at 48 h post mortem. Flavour was similar among breed groups while juiciness was highest for Limousin and lowest for Angus. The juicier beef simultaneously showed the highest drip but the lowest cooking losses. In conclusion, clear differences in meat quality were observed between breeds despite similar IMF contents.

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

Emissions of ammonia, nitrous oxide and methane from different types of dairy manure during storage as affected by dietary protein content

In a storage experiment with dairy cow manure, the effects of dietary protein content and manure type on ammonia, nitrous oxide and methane volatilization as well as overall nitrogen (N) loss from manure were investigated. Early-lactating cows received rations with 175, 150 and 125 g crude protein/kg dry matter. Each ration was tested in four manure storage systems reflecting typical farm conditions. These either contained total excreta with high amounts of straw (deep litter manure) or no straw (slurry) or, proportionately, 0.9 of urine and 0.1 of faeces (urine-rich slurry) complemented by the residuals with a low amount of straw (farmyard manure). Manure samples were stored for 7 weeks under controlled conditions and trace gas emission was repeatedly measured. Reduction of N intake decreased daily N excretion and urine N proportion and, on average, led to 0.7-fold lower storage ammonia emission rates on average. Total storage N loss was simultaneously reduced with the extent depending on urine N proportion of the respective manures. A lower dietary protein content furthermore reduced nitrous oxide emission rates in most manure types but increased methane emission from urine-rich slurry; however, global warming potential (based on trace gas output) of all manures was similar with low and high dietary protein content. In deep litter manure, characterized by the highest C: N ratio, emission rates of total N, ammonia and methane were lowest, whereas nitrous oxide values were intermediate. Substantial emission of nitrous oxide occurred with farmyard manure which also had the highest methane values and, consequently, by far the highest global warming potential. C:N ratio of manure was shown to be suitable to predict total N loss from manure during storage in all manure types whereas urine N proportion and manure pH were only of use with liquid manures.

Evidence for the inhibition of the terminal step of ruminal α-linolenic acid biohydrogenation by condensed tannins

Effects of condensed tannins (CT), either via extract or plant-bound, and saponin extract on ruminal biohydrogenation of alpha-linolenic acid (ALA) were investigated in vitro. Grass-clover hay served as basal diet (control). The control hay was supplemented with extracts contributing either CT from Acacia mearnsii [7.9% of dietary dry matter (DM)] or saponins from Yucca schidigera (1.1% of DM). The fourth treatment consisted of dried sainfoin (Onobrychis viciifolia), a CT-containing forage legume, in an amount also providing 7.9% CT in dietary DM. All diets were supplemented with linseed oil at a level contributing 60% of total dietary ALA in all treatments. Diets were incubated for 10 d (n = 4) in the rumen simulation technique system, using the last 5 d for statistical evaluation. Fatty acids were analyzed in feed, feed residues, incubation fluid, and its effluent. Data were subjected to ANOVA considering diet and experimental run as main effects. Both CT treatments reduced ruminal fiber and crude protein degradation, and lowered incubation fluid ammonia concentration. Only the CT extract suppressed methane formation and shifted microbial populations toward bacteria at cost of protozoa. The saponin extract remained without clear effects on fermentation characteristics except for increased protozoal counts. The extent of ALA biohydrogenation was 20% less with the CT plant, but this probably resulted from reduced organic matter degradability rather than from an inhibition of biohydrogenation. After incubation analysis of incubation fluid effluent and feed residues showed a considerable proportion of the 3 biohydrogenation intermediates, cis-9, trans-11, cis-15 C18:3, trans-11, cis-15 C18:2, and trans-11 C18:1, which did not occur in the initial feeds. Only the CT-extract diet led to a different profile in the effluent compared with the control diet with trans-11 C18:1 being considerably increased at cost of C18:0. This could have been achieved by suppressing protozoa and enhancing the bacterial population, thus removing potential microbes involved in biohydrogenation and increasing competition between bacteria involved in biohydrogenation and others. The elevation of trans-11 C18:1 as the precursor of cis-9, trans-11 conjugated linoleic acid formed in body tissue and mammary gland is probably favorable from a human health point of view.

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.