BAYER, C.

BERNDT, A.

CARVALHO, P. C. de F.

CEZIMBRA, I.

FARIA, B. M. de

GENRO, T. C. M.

PRATES, E. R.

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 52a	  Reunião	  Anual	  da	  Sociedade	  Brasileira	  de	  Zootecnia	  Zootecnia:	  Otimizando	  Recursos	  e	  Potencialidades	  Belo	  Horizonte	  –	  MG,	  19	  a	  23	  de	  Julho	  de	  2015    ________________________________________________________________________________________________________________________________________________    Página 1 de 3  Relações entre consumo e emissão de metano por bovinos em pastagem natural no sul do Brazil  Teresa Cristina Moraes Genro2, Bruna Moscat de Faria3, Ênio Rosa Prates4, Alexandre Berndt5, Ian Cezimbra3, Cimélio Bayer6, Paulo César de Faccio Carvalho7   1Parte da tese de doutorado do segundo autor, financiada pela EMBRAPA (MP1 PECUS) 2Pesquisador A, Embrapa Pecuária Sul- CPPSUL, Bagé, RS. e-mail: cristina.genro@embrapa.br  3Doutoranda PPG Zootecnia da Universidade Federal do Rio Grande do Sul- UFRGS, Porto Alegre, RS. Bolsista da Capes. e-mail: bmzoorural@gmail.com e ian_zootecnia@hotmail.com 4 Professor Visitante do Departamento de Zootecnia da UFRGS. e-mail: rosa30@terra.com.br 5Pesquisador A, Embrapa Pecuária Sudeste- CPPSE, São Carlos, SP. e-mail: alexandre.berndt@embrapa.br 6 Professor Associado do Departamento de Solos da UFRGS. e-mail: cimelio.bayer@ufrgs.br 7 Professor Titular do Departamento de Plantas Forrageiras da UFRGS. e-mail: pcfcarvalho@ufrgs.br  Resumo: Objetivou-se estudar as relações entre a emissão de metano e o consumo de matéria seca e de fibra em detergente neutro em bovinos mantidos em pastagem natural do sul do Brasil. O estudo foi realizado em área pertencente a Embrapa Pecuária Sul, localizada no município de Bagé, Rio Grande do Sul. Foram avaliadas quatro estações do ano de 2013; verão (21 de janeiro), outono (29 de abril), inverno (22 de julho) e primavera (28 de outubro). As avaliações de consumo foram feitas com o auxílio do marcador alcano e as medições de metano emitido pelos animais através do gás traçador hexafluoreto de enxofre (SF6). As relações entre a emissão de metano e o consumo de matéria seca e de fibra em detergente neutro pelos animais em todas as estações do ano, com grande variação entre os animais. O maior coeficiente de determinação foi no verão (R2 = 0,1876 e 0,1834 para o consumo de MS e FDN, respectivamente). A quantidade de alimento consumido diariamente por bovinos de corte mantidos em pastagem natural não esteve associada com as emissões de metano. São necessários mais estudos para determinar quais são os fatores que devem estar influenciando a emissão de metano entérico.  Palavras–chave: alcano, bioma Pampa, consumo diário, FDN, gases efeito estufa  Relationship between intake and methane emission by steers on natural pasture in southern Brazil   Abstract: The objective was to study the relationships between methane emissions and dry matter, and between methane emissions and neutral detergent fiber intake in cattle on natural grassland of Rio Grande do Sul. The study was conducted in the Embrapa Southern Region Animal Husbandry, located in Bagé, RS. Four seasons were evaluated in the year 2013: summer (January 21), fall (April 29), winter (July 22) and spring (October 28). The dry matter intake (DMI) was measured by n-alkanes and the methane emissions using the sulfur hexafluoride technique (SF6). There was a negligible relationship between methane emissions and dry matter, nor between methane emissions and neutral detergent fiber intake for animals in all seasons, with high variation among animals. The best determination coefficient was in summer (R2 = 0.1876 and 0.1834 for the DM and NDF, respectively). The amount of food consumed daily by beef cattle raised on grasslands was not associated with methane emissions. More studies are needed to determine which are the factors that may be influencing the enteric methane emissions.  Keywords: alkane, daily intake, greenhouse gases, NDF, Pampa biome,   Introduction There is little knowledge about the amount of methane emitted by animals in production systems used in South America, especially by animals raised in the Pampa biome. In fact, there are a few data about methane emissions from beef cattle grazing as of yet. Natural and semi-natural pastures are rich in diversity often composed of species of plants with high cell wall content and therefore lower digestibility (Richmond et al., 2015). Ellis et al. (2009) stated that the use of variables such as dry matter intake, metabolizable energy intake, NDF, cellulose and hemicellulose contents in the prediction equations of methane production by beef cattle improve the accuracy of the results. These findings indicate that these variables have a strong influence on the amount of methane produced by animals’ digestion. Thus, the objective was to study the relationships between methane emissions and the dry matter, and between methane emissions and neutral detergent fiber intake in cattle on natural grasslands in southern Brazil.  Material and Methods  52a	  Reunião	  Anual	  da	  Sociedade	  Brasileira	  de	  Zootecnia	  Zootecnia:	  Otimizando	  Recursos	  e	  Potencialidades	  Belo	  Horizonte	  –	  MG,	  19	  a	  23	  de	  Julho	  de	  2015    ________________________________________________________________________________________________________________________________________________    Página 2 de 3  The study was conducted in the Embrapa Southern Region Animal Husbandry, located in Bagé, Rio Grande do Sul. The soil of the area chosen to apply the treatments was of the LUVISSOLO Háplico Pálico abrúptico class. The total area used was 61 ha, subdivided into nine paddocks of about 7 ha each. In the paddocks different intensification levels in the use of natural pasture were tested: natural grassland (NG), natural grassland fertilized with nitrogen (NGF) and natural grassland fertilized with nitrogen and overseeded with exotic cool-season species (NGFS). The species used were annual ryegrass (Lolium multiflorum Lam.) and red clover (Trifolium pratense L.). Treatments were started in the area in 2005. In August 2012, Hereford steers averaging 10 months and 180 kg were introduced into the area to finishing. 27 animals were used for the measurements, three in each paddock. The grazing method was continuous with variable stocking, with enough animals to keep the herbage allowance to 12 kg of dry matter.100 kg-1 of body weight (BW; 12% BW). The experimental design was a complete randomized design with three replications areas. Four seasons were evaluated in the year 2013: summer (January 21), fall (April 29), winter (July 22) and spring (October 28). The animals received cellulose pellets with n-alkane dotriacontane (C32) daily in the morning (8 am) and in the afternoon (4 pm), for 10 days of each experimental period. From the fifth day of dosing, faeces samples were collected twice daily, one in the morning and one in the afternoon, prior the administration of the C32 pellet. The faeces samples from all days of collection per season per animal were thawed, homogenized and a sub-sample per animal per season was made. After drying, the faeces were ground in a Wiley mill with 1 mm sieve, identified and stored for later analysis. Forage samples were collected by hand plucking, one for each animal, dried, ground and stored for analysis. After collection, samples were dried at 55 ◦ C for 72 h, ground and used for the following analyses: DM at 105 ◦ C for 12 hours; organic matter (OM) by burning in a muffle furnace at 550 ◦ C, neutral detergent fiber (NDF) without the use of amylase.  The determination of alkanes present in the forage and the faeces was performed according to the protocol described by Dove and Mayes (2006). To study methane emissions from animals we used the technique of sulfur hexafluoride tracer (SF6). Methane samples were collected close to the animal’s nose for five days per trial period. The methane concentrations and SF6 were determined by gas chromatography.  The relationships between DMI and methane emissions, and between NDF intake (NDFI) and methane emissions per animal evaluated in each season were tested by regression analyses using JMP statistical software (JMP version 9.0.0, 2010).  Results and Discussion There was a negligible relationship between DMI and methane emission (P>0.05) for all seasons studied (Figure 1). Savian et al. (2014) observed positive linear relationship between the dry matter intake and total methane emission in sheep grazing Ryegrass. For this study, the animals had only one specie to choice to intake.. It is worth remembering that in our study the animals were in heterogeneous environment with large specie diversity, where the options to intake of different forage species was high, which may have led to a greater variability between animals.   Figure 1.  Relationships between daily dry matter intake (DMI, kg) and methane emission (g.day-1) by steers. Summer (y = -23.545x + 268.72; R2 = 0.1876; P=0.0725), fall (y = -3.7721x +  52a	  Reunião	  Anual	  da	  Sociedade	  Brasileira	  de	  Zootecnia	  Zootecnia:	  Otimizando	  Recursos	  e	  Potencialidades	  Belo	  Horizonte	  –	  MG,	  19	  a	  23	  de	  Julho	  de	  2015    ________________________________________________________________________________________________________________________________________________    Página 3 de 3  152.20; R2 = 0.0426; P=0.4114), winter (y = -2.1794x + 155.29; R2 = 0.0057; P = 0.7726), spring (y = 3.1145x + 257.50; R2 = 0.0016; P = 0.1832).  Likewise the DMI, no relationship was observed between methane emission and NDFI by the animals (P>0.05) in the different seasons of the year (Figure 2). Pinares-Patiño et al. (2003) observed a good relationship between NDFI and methane emission (r=.61) by cows grazing monospecific pasture of Phleum pratense. However, the correlation between NDFI and methane emissions were not significant in this study. These results showed that the animal's grazing behavior on grasslands, other factors must have been influencing DMI, NDFI and methane emissions. Cezimbra (2015) studied the relationship between structural traits of natural pasture and DMI and its consequences on methane emissions. He found the structural sward traits affect  the DMI and the methane emissions and it explained more than half of DMI an methane emissions variation from the animals grazing grasslands.  Figure 2.  Relationships between daily NDFI (kg) and methane emission (g. day-1) by steers. Summer (y = -33.10x + 276.34; R2 = 0.1834; P=0.0762), fall (y = -5.3556x + 153.77; R2 = 0.0503; P=0.3710), winter (y = -6.9688x + 171.64; R2 = 0.0233; P=0.5589), spring (y = 32.249x + 155.04; R2 = 0.0607; P=0.5540).  Conclusions  The amount of food consumed daily in beef cattle raised on grasslands was not associated with methane emission. More studies are needed to determine which are the factors that may be influencing these variables.  References Cezimbra, I. 2015. Emissão de metano por bovinos sob níveis de oferta de forragem em pastagem nativa do Bioma Pampa. tese (D.Sc.). Universidade Federal do Rio Grande do Sul, Porto Alegre, RS. Dove, H. and Mayes, R. W. 2006. Protocol for the analysis of n-alkanes and other plant-wax compounds and their use as markers for quantifying the nutrient supply of large mammalian herbivores. Nature Protocol 1(4):1680-1697. Ellis, J. L.; Kebreab, E.; Odongo, N. E.; Beauchemin, K.; McGinn, S.; Nkrumah, J. D.; Moore, S. S.; Christopherson, R.; Murdoch, G. K.; McBride, B. W.; Okine, E. K. and France, J. 2009. Modeling methane production from beef cattle using linear and nonlinear approaches. Journal of Animal Science 87:1334-1345. Pinares-Patiño, C. S.; Baumont, R.; Martin, C. 2003. Methane emissions by Charolais cows grazing a monospecific pasture of timothy at four stages of maturity.  Canadian Journal of Animal Science 83(4): 769-777. Richmond, A. S.; Wylie, A. R. G.; Laidlaw, A. S. and Lively, F. O. 2015. Methane emissions from beef cattle grazing on semi-natural upland and improved lowland grasslands. Animal 9(1):130-137. Savian, J. V.; Barth Neto, A.; David, D. B.; Bremm, C.; Schons, R. M. T.; Genro, T. C. M.; Amaral, G. A.; Gere, J.; McManus, C. M.; Bayer, C. and Carvalho, P. C. F. 2014. Grazing intensity and stocking methods on animal production and methane emission by grazing sheep: Implications for integrated crop–livestock system. Agriculture, Ecosystems and Environment 190:112-119. 

Relationship between intake and methane emission by steers on natural pasture in southern Brazil.

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Relationship between intake and methane emission by steers on natural pasture in southern Brazil.

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