Effect of high-sugar grasses on methane emissions simulated using a dynamic model

Centre for Nutrition Modelling, Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada.
Journal of Dairy Science (Impact Factor: 2.57). 01/2012; 95(1):272-85. DOI: 10.3168/jds.2011-4385
Source: PubMed


High-sugar grass varieties have received considerable attention for their potential ability to decrease N excretion in cattle. However, feeding high-sugar grasses alters the pattern of rumen fermentation, and no in vivo studies to date have examined this strategy with respect to another environmental pollutant: methane (CH(4)). Modeling allows us to examine potential outcomes of feeding strategies under controlled conditions, and can provide a useful framework for the development of future experiments. The purpose of the present study was to use a modeling approach to evaluate the effect of high-sugar grasses on simulated CH(4) emissions in dairy cattle. An extant dynamic, mechanistic model of enteric fermentation and intestinal digestion was used for this evaluation. A simulation database was constructed and analysis of model behavior was undertaken to simulate the effect of (1) level of water-soluble carbohydrate (WSC) increase in dietary dry matter, (2) change in crude protein (CP) and neutral detergent fiber (NDF) content of the plant with an increased WSC content, (3) level of N fertilization, and (4) presence or absence of grain feeding. Simulated CH(4) emissions tended to increase with increased WSC content when CH(4) was expressed as megajoules per day or percent of gross energy intake, but when CH(4) was expressed in terms of grams per kilogram of milk, results were much more variable due to the potential increase in milk yield. As a result, under certain conditions, CH(4) (g/kg of milk) decreased. The largest increases in CH(4) emissions (MJ/d or % gross energy intake) were generally seen when WSC increased at the expense of CP in the diet and this can largely be explained by the representation in the model of the type of volatile fatty acid produced. Effects were lower when WSC increased at the expense of NDF, and intermediary when WSC increased at the expense of a mixture of CP and NDF. When WSC increased at the expense of NDF, simulated milk yield increased and, therefore, CH(4) (g/kg of milk) tended to decrease. Diminished increases of CH(4) (% gross energy intake or g/kg of milk) were simulated when DMI was increased with elevated WSC content. Simulation results suggest that high WSC grass, as a strategy to mitigate N emission, may increase CH(4) emissions, but that results depend on the grass composition, DMI, and the units chosen to express CH(4). Overall, this project demonstrates the usefulness of modeling for hypothesis testing in the absence of observed experimental results.

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Available from: Ermias Kebreab, Dec 02, 2014
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    • "These models could be useful for comparing the CH 4 production rates in ruminants fed rations of poor nutritive value based on tropical grasses and in grain-rich diets (Kurihara et al. 1999). The amount of soluble sugars in the forage can also have some relationships with the methane emissions (Ellis et al. 2012). Valdivia-Salgado et al. (2013) concluded through the stoichiometric technique that supplementation with Brosimum alicastrum foliage to a ration based on poor quality guinea grass (Panicum maximum) hay did not had effects on ruminal methane emissions in sheep (table 9). "
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    ABSTRACT: Ruminant feeding in tropical regions is characterized by grass grazing. Throughout the year, grasses show variations in their availability and quality. Therefore, modern feeding systems must consider the energy requirements of the animal and the degree in which a feed or a combination of several of them could cover the nutritional requirements of the different species and physiological conditions. The central reaction for obtaining energy is carry out in the rumen in the anaerobic fermentation of the carbohydrates present in the feed. This process is developed by the ruminal microorganisms, with the purpose of generating energy for the microbial growth and the concomitant production of volatile fatty acids, methane, carbon dioxide and fermentation heat. For improving meat and milk production and quality in tropical regions, different options have been created for manipulating the energy metabolism of ruminants. Silvopastoral systems, based on Leucaena leucocephala and Panicum maximum association, allow attaining live weight gains of 770 g/d in growing cattle. It is essential the identification of Bos indicus cattle breeds or crosses with lower requirements of metabolizable energy (ME) for maintenance, so as the energy efficiency of meat production could be increased. For milk, it is possible to increase the concentration of unsaturated fatty acids (CLA's) by the tannin presence in the foliages that due to its beneficial effect on human health, could supply aggregate value to the cow's milk. Feeding practices are necessary for reducing the caloric increase of the feeding and that decrease methane emissions from the rumen through the effect of some foliages and fruits that possess secondary metabolites capable of affecting ruminal fermentation.
    Cuban Journal of Agricultural Science 01/2014; 48(1). · 0.05 Impact Factor
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    • "Methane production in ruminants depends on the physical and chemical characteristics of the ration consumed, type of carbohydrates present in the ration, pattern of rumen fermentation and rate of passage of digest from the rumen (Kurihara et al. 1999). Rumen fermentation of cellulose and hemicellulose results in a high ratio of acetate : propionate (Ac : Pr) and high production of methane (Ellis et al. 2012). "
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    ABSTRACT: The aim of the work was to determine the effect of increasing concentrations of saponins from Yucca schidigera in the diet on voluntary intake, rumen fermentation and methane (CH 4) production in Pelibuey sheep fed a tropical grass Pennisetum purpureum. Five male sheep (32.2 AE 1.1 kg liveweight) were fed chopped P. purpureum grass in a 5 · 5 Latin square design. Sheep were supplemented with 0.0, 1.5, 3.0, 4.5 or 6.0 g per day of saponins from Y. schidigera mixed with ground corn, before the grass was offered. Feed intake, feed refusal and total faecal output were recorded for 20 days of the adaptation period and 5 days of the experimental period. Apparent digestibility of dry matter (DMD), organic matter (OMD), neutral detergent fibre (NDFD) and acid detergent fibre (ADFD) were determined. Ruminal methane emission was estimated using stoichiometric balance and the molar proportion of volatile fatty acids was determined by gas chromatography. Voluntary intake, DMD, OMD, NDFD, ADFD, volatile fatty acids and CH 4 emission were not affected (P > 0.05) by increasing inclusion levels of saponins in the ration of sheep. Nonetheless, CH 4 production increased as the voluntary intake of NDF augmented. Addition of 6 g of saponins per day as a supplement to Pelibuey sheep fed a tropical grass did not affect voluntary intake and digestibility of DM, OM, NDF and ADF, or ruminal methane production.
    Animal Production Science 01/2014; 54(10). DOI:10.1071/AN14296 · 1.29 Impact Factor
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    • "Rates of ruminal CH 4 production are higher when ruminants are fed low nutritive quality rations based on tropical grasses than when they are fed concentrate rich rations (Kurihara et al., 1999). The amount of soluble sugars in grasses may also have some bearing on methane emissions (Ellis et al., 2012). As millions of cattle graze low nutritive quality tropical pastures in Central and South America, contributing to global CH 4 emissions, there is scope to reduce enteric CH 4 production in grazing ruminants in the tropical regions of Latin America. "
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    ABSTRACT: Foliages and pods of tropical legumes are alternative feeds for sheep which may contribute to improvement of their productive performance, and secondary metabolites such as tannins and saponins in the pods of Acacia pennatula and Enterolobium cyclocarpum may contribute to reducing methane production in the rumen. Rumen stoichiometry is a method by which methane production can be estimated. Our aim was to determine feed intake, apparent digestibility and methane production in hair sheep fed ground pods of two tropical legumes. Twelve male Pelibuey hair sheep were used in a completely randomized design with three treatments being: (1) control [commercial concentrate], (2) A. pennatula: substitution of 0.45 of ration dry matter (DM) with ground pods of A. pennatula and (3) E. cyclocarpum: substitution of 0.45 of ration DM with ground pods of E. cyclocarpum. There were no differences in DM intake between rations containing pods of legumes (1155 and 1122 g/d for A. pennatula and E. cyclocarpum, respectively), although there were differences (P<0.05) in DM intake between A. pennatula and control (933 g/d). Digestible organic matter intake did not differ among treatments, being 698, 737 and 730 g/d for control, A. pennatula and E. cyclocarpum, respectively. Apparent DM digestibility differed (P<0.05), with the control having the highest digestibility (0.84) relative to A. pennatula and E. cyclocarpum. There was no difference (P>0.05) in conversion efficiency of hexose to volatile fatty acids in the rumen with the control treatment which showed the highest efficiency (0.79), followed by E. cyclocarpum and A. pennatula (0.76). Energy loss as methane (kJ/mol) was not different (P>0.05) among treatments, with the control showing the lowest loss (195.7), followed by E. cyclocarpum (219.2) and A. pennatula (236.6). Further research is required to evaluate effects of the tannins and saponins in the pods of tropical legumes on rumen methanogenesis under practical sheep farming conditions.
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