Abstract. Dietary carbohydrate effects on methane emission from cows and their slurry were measured on an individual animal basis. Twelve dairy cows were fed three of six diets each (n = 6 per diet) of a forage-to-concentrate ratio of 1:1 (dry matter basis), and designed to cover the cows' requirements. The forages consisted of maize and grass silage, and hay. Variations were exclusively accomplished in the concentrates which were either rich in lignified or non-lignified fiber, pectin, fructan, sugar or starch. To measure methane emission, cows were placed into open-circuit respiration chambers and slurry was stored for 14 weeks in 60-L barrels with slurry being intermittently connected to this system. The enteric and slurry organic matter digestibility and degradation was highest when offering Jerusalem artichoke tubers rich in fructan, while acid-detergent fiber digestibility and degradation were highest in cows and slurries with the soybean hulls diet rich in non-lignified fiber. Multiple regression analysis, based on nutrients either offered or digested, suggested that, when carbohydrate variation is done in concentrate, sugar enhances enteric methanogenesis. The methane emission from the slurry accounted for 16.0 to 21.9% of total system methane emission. Despite a high individual variation, the methane emission from the slurry showed a trend toward lower values, when the diet was characterized by lignified fiber, a diet where enteric methane release also had been lowest. The study disproved the assumption that a lower enteric methanogenesis, associated with a higher excretion of fiber, will inevitably lead to compensatory increases in methane emission during slurry storage.

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Aims: To identify the most effective mixture of non-esterified lauric (C 12 ) and myristic (C 14 ) acid in suppressing ruminal methanogenesis, and to investigate their effects on the methanogenic population. Methods and Results: C 12 /C 14 mixtures were incubated with rumen fluid using the Hohenheim gas test apparatus. Methane production and the numbers of Archaea declined with an increasing proportion of C 12 . With a 2 : 1 proportion of C 12 /C 14 , the maximum methane-suppressing effect (96%) was achieved similar to that with C 12 alone. The proportions of the individual methanogenic orders of total methanogens were altered by varying the C 12 /C 14 ratio. Conclusions: Although C 14 alone had no effect on methanogenesis, C 14 enhanced the methane-suppressing effect of C 12 in certain mixtures. Significance and Impact of the Study: The results support strategies for an environment-friendly ruminant nutrition as it was demonstrated that part of the less palatable C 12 could be replaced by C 14 without losing its methane-suppressing potential.

M. 2004. Effect of feed carbohydrates with contrasting properties on rumen fermentation and methane release in vitro. Can. J. Anim. Sci. 84: 265-276. The RUSITEC system was used to test eight diets where the supplements differed in their main carbohydrate source. The forage-to-supplement ratio was 1:1. The eight feeds characterizing the supplements by specific carbohydrates were oat hulls (modeling lignified fiber), soybean hulls (non-lignified fiber), apple pulp (pectin), sugar beet pulp (hemicelluloses and pectin), guar gum (galactomannan), Jerusalem artichoke tubers (fructan), molasses (sucrose), and wheat (starch). Supplements were isoenergetic and iso-nitrogenous. The dietary carbohydrate fractions were analyzed in detail with a combination of enzymatic and chemical methods. The methane release (mmol g -1 degraded organic matter) increased in the order of diets characterized by oat hulls (0.92), guar gum (0.99), wheat (1.04), soybean hulls (1.13), apple pulp (1.15), Jerusalem artichoke (1.21), sugar beet pulp (1.24), and molasses (1.37). According to multiple regression analysis, diets with high sugar content enhanced methane release while methane was low with high dietary lignin content. Regressions also showed that different fibrous carbohydrates had only a minor effect on methane release, probably due to lignification of the fiber. The present results suggest that equations for the estimation of methane emission of ruminants should consider dietary carbohydrate composition and lignin content. Les huit aliments modifiant le supplément par leur source de glucides étaient la balle d'avoine (modélisation de la cellulose lignifiée), la pellicule de soja (cellulose non lignifiée), la pulpe de pomme (pectine), la pulpe de betterave sucrière (hémicelluloses et pectine), la gomme de guar (galactomannane), le topinambour (fructane), la mélasse (sucrose) et le blé (amidon). Les suppléments contenaient la même quantité d'azote et d'énergie. Les auteurs ont analysé soigneusement la fraction de glucides alimentaires par des méthodes chimiques et enzymatiques. Le volume de méthane libéré (mmol par gramme de matière organique dégradée) augmente dans l'ordre suivant : balle d'avoine (0,92), gomme de guar (0,99), blé (1,04), pellicule de soja (1,13), pulpe de pomme (1,15), topinambour (1,21), pulpe de betterave sucrière (1,24) et mélasse (1,37). Selon l'analyse par régression multiple, les rations à forte teneur en sucre accroissent les dégagements de méthane, qui sont plus faibles avec les régimes riches en lignine. Les régressions montrent aussi que les divers hydrates de carbone fibreux n'ont qu'une incidence minime sur la libération de méthane, sans doute à cause de la lignification de la cellulose. Les résultats donnent à penser que les équations servant à estimer les dégagements de méthane par les ruminants devraient tenir compte de la composition des hydrates de carbone et de la concentration de lignine dans la ration.

Hemicelluloses, cellulose, and lignin contents of contrasting feeds, with emphasis on concentrate ingredients and complete concentrates, were analyzed using the Van Soest detergent procedure (analyzing neutral detergent fiber, acid detergent fiber, and acid detergent lignin) and the enzymatic-chemical procedure (analyzing cellulose, soluble and insoluble noncellulosic polysaccharides, and Klason lignin). Also, feces from cows fed concentrates differing in carbohydrate composition were analyzed by the 2 procedures. The correlation between acid detergent lignin and Klason lignin was significant, but not as close as the one between individual structural polysaccharides measured with the 2 procedures. The correlation between the results of the 2 procedures was highly significant for apparent cellulose digestibility, as were the correlations between digestibilities of hemicelluloses with total as well as with insoluble noncellulosic polysaccharides. The relationship between dietary lignin content and fiber digestibility was weak. The exclusion of a group of cows fed a concentrate with apple pulp, however, improved the respective correlations. Klason lignin correlated more closely with the measured fiber digestibility than acid detergent lignin. The study showed that results of the detergent method were comparable to those of the enzymatic-chemical method with cellulose, hemicelluloses, and their digestibilities. However, acid detergent lignin was much lower than Klason lignin. When the carbohydrate composition of concentrate varied widely, lignin was not suitable for the prediction of fiber digestibility.

Inoculants of lactic acid bacteria (LAB) are used to improve silage quality and prevent spoilage via increased production of lactic acid and other organic acids and a rapid decline in silage pH. The addition of LAB inoculants to silage has been associated with increases in silage digestibility, dry matter intake (DMI), and milk yield. Given the potential change in silage and rumen fermentation conditions accompanying these silage additives, the aim of this study was to investigate the effect of LAB silage inoculants on DMI, digestibility, milk yield, milk composition, and methane (CH4) production from dairy cows in vivo. Eight mid-lactation Holstein-Friesian dairy cows were grouped into 2 blocks of 4 cows (multiparous and primiparous) and used in a 4×4 double Latin square design with 21-d periods. Methane emissions were measured by indirect calorimetry. Treatments were grass silage (mainly ryegrass) with no inoculant (GS), with a long-term inoculant (applied at harvest; GS+L), with a short-term inoculant (applied 16h before feeding; GS+S), or with both long and short-term inoculants (GS+L+S). All diets consisted of grass silage and concentrate (75:25 on a dry matter basis). The long-term inoculant consisted of a 10:20:70 mixture of Lactobacillus plantarum, Lactococcus lactis, and Lactobacillus buchneri, and the short-term inoculant was a preparation of Lc. lactis. Dry matter intake was not affected by long-term or short-term silage inoculation, nor was dietary neutral detergent fiber or fat digestibility, or N or energy balance. Milk composition (except milk urea) and fat and protein-corrected milk yield were not affected by long- or short-term silage inoculation, nor was milk microbial count. However, milk yield tended to be greater with long-term silage inoculation. Methane expressed in units of grams per day, grams per kilogram of DMI, grams per kilogram of milk, or grams per kilogram of fat and protein-corrected milk yield was not affected by long- or short-term silage inoculation. However, CH4 expressed in units of kilojoules per kilogram of metabolic body weight per day tended to be greater with long-term silage inoculation. Results of this study indicate minimal responses in animal performance to both long- and short-term inoculation of grass silage with LAB. Strain and dose differences as well as different basal silages and ensiling conditions are likely responsible for the lack of significant effects observed here, although positive effects have been observed in other studies.

The in vitro gas production (GP) technique has been widely used for feed evaluation. However, variability in results limits useful comparisons. Results from a ring test undertaken in four laboratories (Italy – IT, Spain – SP, Wales – WA and Denmark – DK) using the same wireless equipment (ANKOM Technology), same substrates and same laboratory protocol are presented, including calculation of repeatability and reproducibility according to ISO 5725-2. Hay, maize starch and straw samples and units without sample (blanks) were incubated in five repetitions using rumen inoculum from cows (DK, IT and WA) or sheep (SP). Curves, corrected for blanks, were fitted using an exponential regression model with a lag time. The following variables were considered: (i) GP24 and GP48: raw values at 24 and 48 h (mL/g DM), corrected for blanks; (ii) A: asymptotic GP (mL/g DM); (iii) T1/2: time when half A is produced (h); (iv) GPMR: maximum predicted GP rate (mL/h); (v) L: lag time (h). A mixed model including laboratories as random effect was used. A significant interaction between substrate and laboratories was found for all variables except A. The most repeatable and reproducible results were observed for A and GP48. The results from this ring test suggest the need for more standardisation, particularly in the procedures that occur outside the laboratory.