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Greenhouse gases (GHG) can be affected by grazing intensity, soil, and climate variables. This study aimed at assessing GHG emissions from a tropical pasture of Brazil to evaluate (i) how the grazing intensity affects the magnitude of GHG emissions; (ii) how season influences GHG production and consumption; and (iii) what are the key driving variables associated with GHG emissions. We measured under field conditions, during two years in a palisade-grass pasture managed with 3 grazing intensities: heavy ( 15cm height), moderate (25 cm height), and light (35 cm height) N 2 O, CH 4 and CO 2 fluxes using static closed chambers and chromatographic quantification. The greater emissions occurred in the summer and the lower in the winter. N 2 O, CH 4 , and CO 2 fluxes varied according to the season and were correlated with pasture grazing intensity, temperature, precipitation, % WFPS (water-filled pores space), and soil inorganic N. The explanatory variables differ according to the gas and season. Grazing intensity had a negative linear effect on annual cumulative N 2 O emissions and a positive linear effect on annual cumulative CO 2 emissions. Grazing intensity, season, and year affected N 2 O, CH 4 , and CO 2 emissions. Tropical grassland can be a large sink of N 2 O and CH 4 . GHG emissions were explained for different key driving variables according to the season.

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Neste estudo, foram realizados dois ensaios com os objetivos de avaliar o fracionamento dos carboidratos de alimentos volumosos e estimar a digestibilidade desses nutrientes em dois ensaios de digestão com eqüinos. No ensaio 1, foram utilizados cinco eqüinos em delineamento de blocos casualizados, com sete tratamentos - fenos de alfafa (Medicago sativa); amendoim forrageiro (Arachis pintoi); desmódio (Desmodium ovalifolium); guandu (Cajanus cajan); macrotiloma (Macrotyloma axillare); estilosantes (Stylosanthes guianensis); ou coastcross (Cynodon dactylon) - avaliados pela técnica de sacos de náilon móveis. No ensaio 2, foram utilizados quatro eqüinos em delineamento quadrado latino 4 × 4, alimentados com feno de coastcross em quatro tipos de moagem com o objetivo de avaliar se a redução do tamanho de partícula interfere na digestibilidade dos carboidratos. Os resultados comprovaram que os eqüinos possuem alta eficiência na digestão dos carboidratos não-fibrosos e de suas frações hidrolisáveis e rapidamente fermentáveis. Os fenos de amendoim forrageiro, estilosantess e macrotiloma apresentaram elevada digestibilidade dos carboidratos fibrosos e não-fibrosos, enquanto a digestibilidade de todos os nutrientes do amendoim forrageiro foi superior a 70%, o que indica potencial para uso desta leguminosa em dietas para eqüinos. O processamento do feno de coastcross não influenciou a digestibilidade das frações dos carboidratos fibrosos e não-fibrosos. A análise dos carboidratos fibrosos e não-fibrosos é um bom indicativo do valor nutricional dos alimentos e pode ser incluída na avaliação da qualidade de alimentos para eqüinos.

RESUMO -Objetivou-se estimar a digestibilidade de nutrientes de forrageiras em eqüinos utilizando-se a técnica de sacos de náilon móveis. Foram avaliados alfafa (Medicago sativa), amendoim forrageiro (Arachis pintoi), desmódio (Desmodium ovalifolium), estilosantes (Stylosanthes guianensis), guandu (Cajanus cajan), macrotiloma (Macrotyloma axillare) e capimcoastcross (Cynodon dactylon cv. coastcross). O delineamento foi em blocos inteiramente casualizados com sete alimentos e cinco blocos (animais). Foram utilizados cinco eqüinos mestiços com 17 a 27 anos de idade e peso vivo médio de 350 kg.O ensaio teve duração de 12 dias: três para a adaptação às baias, cinco para inserção gástrica dos sacos através de sonda nasogástrica e quatro de coleta dos sacos nas fezes. No período pré-experimental de 30 dias, os animais foram mantidos em piquetes com dieta composta de 80% de feno de coastcross e 20% de concentrado. Na confecção dos sacos, utilizou-se náilon com porosidade de 45 μ e dimensão de 7,5 × 2 cm. Em cada saco, foram inseridos 510 mg de matéria seca de amostra do alimento.Os coeficientes de digestibilidade dos nutrientes das forragens foram calculados considerando o resíduo obtido no saco. A digestibilidade dos nutrientes do amendoim, estilosantes e macrotiloma foram superiores à da demais forrageiras, com destaque para a digestibilidade da proteína bruta, cujos valores foram de 91,4; 94,9 e 97,0%, respectivamente. O amendoim e macrotiloma apresentaram digestibilidade da fibra em detergente neutro de 72,3 e 65,2% e da fibra em detergente ácido de 70,9 e 59,4%, respectivamente. O amendoim forrageiro, macrotiloma e estilosantes apresentam digestibilidade dos nutrientes satisfatória e têm potencial para o uso em dietas para eqüinos.Palavras-chave: cavalos, digestão, fibra, forragem Nutrient digestibility of forage feed determined using mobile bag technique in horsesABSTRACT -This work was carried out to evaluate the nutrient digestibility of forages using mobile bags technique in horses. The forages were lucerne (Medicago sativa), peanut (Arachis pintoi), desmodio (Desmodium ovalifolium), stylo (Stylosanthes guianensis), pigeon pea (Cajanus cajan), lime-yellow pea (Macrotyloma axillare) and coastcross (Cynodon dactylon cv. coastcross). A randomized block design was used with seven treatments (feeds) and five blocks (horses). Five crossbreed horses were used with age ranging from 17 to 27 years and average weight of 350 kg. The assay lasted 12 days, being three days for adaptation to barns, five days for nasogastric insertion of bags and four days for bags collection in feces.The diet of horses was composed of 80% of coastcross hay and 20% of commercial concentrate. During the pre-experimental period of 30 days, the horses were maintained in paddocks feeding the diet. Nylon cloth had 45μ pore size, and bags presented dimensions of 7,5 × 2 cm with 510 mg of DM of forage sample/bag. The nutrient digestibility of forages were calculated through residues inside the bags. The nutrient digestibility of peanut, stylo and l...

Soil carbon dioxide emission (ECO2) is a process determined by biotic and abiotic factors in uenced by land use and management practices. In grassland ecosystems, grazing intensity may a ect C input from plants into soil, and thus may also change soil respiration rate. Indeed, limited information is available regarding the e ects of grazing management on ECO2. is study was conducted to evaluate ECO2 seasonal variation, and its relationship to soil temperature (Tsoil) and precipitation, in an area with di erent pasture heights of Marandu palisade grass [Brachiaria brizantha (A.Rich.) Stapf.]. e pasture heights (15, 25, and 35 cm) were distributed in a completely randomized design with 12 repetitions in each area. e evaluations of ECO2 and Tsoil occurred from January 2011 to February 2013, totaling 73 d of observation that were distributed according to climatic seasons. e results showed that seasonal variation of ECO2 was directly related to variations in precipitation and Tsoil. Soil CO 2 emission was higher in summer and lower in winter. e data variability of ECO2 was higher in rainy, hot summers than in dry, cold winters. A positive linear association between ECO2 and Tsoil was observed in summer and autumn. In most seasons measured, ECO2 reduced with increasing pasture height. Accordingly, 2-yr data indicated that accumulated ECO2 decreased with increasing pasture height. us to better understand the e ect of pasture height on ECO2, a shorter period of measurements is not suitable since a di erent result was observed in the rst year of evaluation.

ResumoO objetivo com este trabalho foi avaliar os efeitos de índices de área foliar residual (IAFr), anos de avaliação e ciclos de pastejo sobre as características morfogênicas e estruturais do capim-xaraés sob pastejo, em dois verões agrostológicos (anos de avaliação). O experimento foi conduzido na Universidade Estadual Paulista "Júlio de Mesquita Filho" -UNESP, Campus de Jaboticabal, São Paulo, Brasil e as intensidades de pastejos foram definidas por quatro IAFr: 0,8; 1,3; 1,8 e 2,3. Quando o dossel interceptou 95% da luz incidente, os animais foram colocados no piquete para o pastejo e permaneceram até que o IAFr alvo foi alcançado. Os pastejos foram realizados por vacas da raça Holandesa (Bos taurus taurus L.) não lactantes, utilizando-se a técnica de mob-stocking. As características morfogênicas e estruturais do capim-xaraés respondem de forma efetiva as mudanças nas condições climáticas. Observa-se variabilidade nas características morfogênicas e estruturais em respostas aos anos de avaliação e ciclos de pastejo dentro de ano. Palavras-chave: Brachiaria, índice de área foliar residual, interceptação de luz, Urochloa AbstractThe aim of this study was to evaluate the effects of residual leaf area index (rLAI), years of evaluation and grazing cycles on the morphogenetic and structural characteristics of xaraés palisadegrass subjected to grazing intensities in two summers (years of evaluation). The experiment was carried out at the Universidade Estadual Paulista "Júlio de Mesquita Filho" -UNESP, Campus de Jaboticabal, São Paulo, Brasil and the intensities of grazing were defined by four rLAI: 0.8, 1.3, 1.8 and 2.3. When the canopy intercepted 95% of incident light, the animals were placed on the pasture for grazing and kept until the rLAI target has been reached. Pastures were grazed by non-lactating Holstein cows (Bos Taurus Taurus L.), using the technique of mob-stocking. The morphogenetic and structural characteristics of xaraés palisadegrass respond effectively to weather conditions. There is variability in morphogenetic and structural characteristics in response to years and grazing cycles within years.

Increasing attention is being paid to the importance of N 2 O emissions due to livestock activities in tropical countries. Understanding the key variables driving N 2 O emission could help minimize impacts of N 2 O release and improve the accuracy of N 2 O inventories. We aimed to investigate the effects of soil moisture, soil compaction, urine composition, urine volume, and dung addition on N 2 O emissions from a urine-treated tropical Ferralsol under controlled conditions. Manipulated soil conditions (e.g., moisture content, compaction, and dung addition) affected N 2 O emissions when varying quantities of urine-N (p = 0.02) were applied (urine volumes remained equal) and when varying urine volumes (p = 0.04) were applied (quantities of urine-N remained equal). When the amount of urine-N applied was varied, the estimated N 2 O emission factor (EF) was 3.14 ± 0.70%, 2.29 ± 1.25%, 3.90 ± 0.64%, 4.73 ± 0.88%, and 6.62 ± 1.10% for moist soil, dry soil, compacted soil, plus dung, and plus dung and compacted soil treatments, respectively. While varying the volume of urine, the estimated N 2 O EF was 4.96 ± 1.66%, 4.27 ± 1.42%, 3.99 ± 1.19%, 6.50 ± 0.35%, and 7.37 ± 0.76% for moist, dry soil, compacted soil, plus dung, and plus dung and compacted soils treatments, respectively. The urine-N concentration influenced N 2 O emissions (p = 0.02) [which decreased linearly (p = 0.062)] as well the volume of urine (p < 0.01) [which increased linearly (p < 0.01)]. The chemical form of the applied urine-N (urea, nitrate, or ammonium) did not affect N 2 O emissions and the emissions factor averaged 1.40 ± 0.38%. N 2 O production was affected by the KCl concentration in the urine (p < 0.01), and the effect was curvilinear. The key driving factor affecting N 2 O emissions was soil moisture content. The N 2 O response varied when the urine volume differed (in both moist and dry soil conditions), and with the addition of dung.