Emissão de N2O, CH4 e NH3 nas excretas de bovinos de corte suplementados com proteína não degradável no rúmen durante a recria
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Data
2021-03-19
Autores
Carvalho, Geovany Macêdo
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Universidade Estadual Paulista (Unesp)
Resumo
A atividade pecuária no Brasil tem um importante papel em atender a demanda mundial por alimento, contudo, o setor é responsável por emitir uma quantidade considerável de gases de efeito estufa (GEE) e amônia. A excreção de N através das fezes e urina dos ruminantes são fontes principalmente de óxido nitroso e amônia, e a nutrição pode ser uma estratégia na redução da emissão destes gases. O objetivo deste estudo foi avaliar o efeito do uso da suplementação com proteína não degradável no rúmen (PNDR) nas emissões de N2O, CH4 e NH3 das fezes e urina de bovinos de corte na fase de recria em Urochloa brizantha cv. Xaraés. A área de avaliação da emissão de gases possuía 0,8 ha formados por pastagem de capim Urochloa brizantha cv. Xaraés, que foi excluída do acesso dos animais 6 meses antes da aplicação dos tratamentos. O delineamento experimental utilizado foi o DBC (delineamento em blocos casualizados), com 5 blocos (local de aplicação da excreta no solo), em esquema fatorial (2 x 2 x 2), com 2 tipos de suplementos na alimentação do animal (suplementação com sal mineral ad libitum ou com glúten de milho a 0,3% do peso vivo como fonte de PNDR + sal mineral ad libitum), 2 fontes de emissão de gases (urina e fezes) e 2 períodos de aplicação das excretas (meio e fim da recria). As fezes e urinas implantadas no solo foram coletadas de novilhos Nelore, mantidos em pastagem de capim Urochloa brizantha cv. Xaraés e suplementados, conforme tratamentos descritos anteriormente, as 09h00m. As amostragens das excretas dos animais dos tratamentos ocorreram em dois períodos, meio (Janeiro) e fim (Março) da fase de recria dos animais e as aplicações ao solo em Fevereiro (Meio) e Abril (Fim). Foram incluídas 5 câmaras sem a aplicação de fezes ou urina para avaliar as emissões derivadas do sistema solo e liteira que foram deduzidas dos tratamentos (emissão basal do solo). Deste modo, a área experimental era constituída de 25 parcelas. Cada câmara de avaliação das emissões de N2O e CH4 constitui uma parcela. Em outras duas áreas próximas às parcelas de avaliação de gases, com mais 25 parcelas cada, foram também implantados os mesmos tratamentos ao solo, nas mesmas datas para amostragem de solo e para avaliação de amônia volatilizada. Houve uma tendência a interação entre tipo de suplemento, período da recria e tipo de excreta sobre o fator de emissão de NH3 (P = 0,0585). A urina dos animais que receberam ou não suplementação com PNDR apresentaram maiores perdas de N na forma de NH3 no fim da recria em relação ao observado no meio do período de recria, sendo também superiores às perdas de N via fezes, as quais não apresentaram diferença entre os tipos de suplemento e períodos de avaliação. A emissão acumulada de CH4 foi afetada pelo período (P = 0,0319), entretanto, não foi observado efeito dos tipos de excretas (P = 0,1607) e tipos de suplementos (P = 0,1143) e interações. No período do meio da recria foi observada maior emissão acumulada de CH4, quando comparada com a emissão acumulada de CH4 no fim da recria. Os fatores de emissão das fezes não foram afetados pelo período (P = 0,1381), tipo de suplemento (P = 0,5262) e interação. A emissão de N2O não foi afetada pelos períodos (P = 0,4698), tipos de excretas (P = 0,8265), tipos de suplementos (P = 0,8707) e interações. Os fatores de emissão de N2O não foram afetados pelos períodos (P = 0,4492), tipos de excretas (P = 0,7575), tipos de suplementos (P = 0,7411) e interações. Conclui-se que efeito da suplementação de bovinos de corte na fase de recria com PNDR sobre as emissões de NH3 e CH4 é dependente do período e tipo de excreta. Porém não foram observados efeitos sobre a emissão de N2O. Os fatores de emissão de N2O, NH3 e CH4 das excretas de bovinos de corte na fase de recria estão abaixo dos valores preconizados pelo IPCC, superestimando a quantidade emitida pela atividade em nossas condições de criação em clima tropical.
The livestock activity in Brazil has an important role in meeting the world demand for food, however, the sector is responsible for emitting a considerable amount of greenhouse gases (GHG) and ammonia. The excretion of N through the feces and urine of ruminants are mainly sources of nitrous oxide and ammonia, and nutrition can be a strategy to reduce the emission of these gases. The aim of this study was to evaluate the effect of using supplementation with non-degradable rumen protein (RUP) on N2O, CH4 and NH3 emissions from the feces and urine of beef cattle during the rearing phase in Urochloa brizantha cv. Xaraés. The gas emission assessment area had 0.8 ha formed by pasture grass Urochloa brizantha cv. Xaraés, who was excluded from the animals' access 6 months before the treatments were applied. The experimental design used was the DBC (randomized block design), with 5 blocks (place of application of excreta in the soil), in a factorial scheme (2 x 2 x 2), with are 2 types of supplements in the animal's diet (supplementation with salt mineral ad libitum or with corn gluten at 0.3% of live weight as a source of RUP + mineral salt ad libitum), 2 sources of gas emissions (urine and faeces) and 2 application of periods of excreta (middle and end of application) recreates). The feces and urine implanted in the soil were collected from Nelore steers, kept in Urochloa brizantha cv. Xaraés and supplements, according to treatments described above, at 9:00 am. The sampling of the animals 'excreta from the treatments occurred in two periods, half (January) and end (March) of the animals' rearing phase and the applications to the soil in February (Middle) and April (End). Five chambers were included without the application of faeces or urine to assess the emissions derived from the soil and litter system that were deducted from the treatments (basal emission from the soil). In this way, the experimental area consisted of 25 plots. Each N2O and CH4 emissions assessment chamber constitutes a portion. In two other areas close to the gas assessment plots, with a further 25 plots each, the same soil treatments were also implemented, on the same dates for soil sampling and for the evaluation of volatilized ammonia. There was a tendency for interaction between type of supplement, breeding period and type of excreta on the NH3 emission factor (P = 0.0585). The urine of animals that received or did not receive RUP supplementation showed greater losses of N in the form of NH3 at the end of the rearing than in the middle of the rearing period, also being higher than the losses of N via faeces, which showed no difference. between supplement types and evaluation periods. The accumulated CH4 emission was affected by the period (P = 0.0319), however, there was no effect of the types of excreta (P = 0.1607) and types of supplements (P = 0.1143) and interactions. In the middle of the rearing period, a greater accumulated CH4 emission was observed, when compared to the accumulated CH4 emission at the end of the rearing. The emissions factor of faeces was not affected by the period (P = 0.1381), type of supplement (P = 0.5262) and interaction. N2O emissions were not affected by periods (P = 0.4698), types of excreta (P = 0.8265), types of supplements (P = 0.8707) and interactions. The emissions factors N2O were not affected by periods (P = 0.4492), types of excreta (P = 0.7575), types of supplements (P = 0.7411) and interactions. It is concluded that the effect of supplementation of beef cattle in the rearing phase with RUP on NH3 and CH4 emissions is dependent on the period and type of excreta. However, no effects on N2O emission were observed. The emission factors of N2O, NH3 and CH4 from the excreta of beef cattle in the rearing phase are below the values recommended by the IPCC, overestimating the amount emitted by the activity in our conditions of breeding in a tropical climate.
The livestock activity in Brazil has an important role in meeting the world demand for food, however, the sector is responsible for emitting a considerable amount of greenhouse gases (GHG) and ammonia. The excretion of N through the feces and urine of ruminants are mainly sources of nitrous oxide and ammonia, and nutrition can be a strategy to reduce the emission of these gases. The aim of this study was to evaluate the effect of using supplementation with non-degradable rumen protein (RUP) on N2O, CH4 and NH3 emissions from the feces and urine of beef cattle during the rearing phase in Urochloa brizantha cv. Xaraés. The gas emission assessment area had 0.8 ha formed by pasture grass Urochloa brizantha cv. Xaraés, who was excluded from the animals' access 6 months before the treatments were applied. The experimental design used was the DBC (randomized block design), with 5 blocks (place of application of excreta in the soil), in a factorial scheme (2 x 2 x 2), with are 2 types of supplements in the animal's diet (supplementation with salt mineral ad libitum or with corn gluten at 0.3% of live weight as a source of RUP + mineral salt ad libitum), 2 sources of gas emissions (urine and faeces) and 2 application of periods of excreta (middle and end of application) recreates). The feces and urine implanted in the soil were collected from Nelore steers, kept in Urochloa brizantha cv. Xaraés and supplements, according to treatments described above, at 9:00 am. The sampling of the animals 'excreta from the treatments occurred in two periods, half (January) and end (March) of the animals' rearing phase and the applications to the soil in February (Middle) and April (End). Five chambers were included without the application of faeces or urine to assess the emissions derived from the soil and litter system that were deducted from the treatments (basal emission from the soil). In this way, the experimental area consisted of 25 plots. Each N2O and CH4 emissions assessment chamber constitutes a portion. In two other areas close to the gas assessment plots, with a further 25 plots each, the same soil treatments were also implemented, on the same dates for soil sampling and for the evaluation of volatilized ammonia. There was a tendency for interaction between type of supplement, breeding period and type of excreta on the NH3 emission factor (P = 0.0585). The urine of animals that received or did not receive RUP supplementation showed greater losses of N in the form of NH3 at the end of the rearing than in the middle of the rearing period, also being higher than the losses of N via faeces, which showed no difference. between supplement types and evaluation periods. The accumulated CH4 emission was affected by the period (P = 0.0319), however, there was no effect of the types of excreta (P = 0.1607) and types of supplements (P = 0.1143) and interactions. In the middle of the rearing period, a greater accumulated CH4 emission was observed, when compared to the accumulated CH4 emission at the end of the rearing. The emissions factor of faeces was not affected by the period (P = 0.1381), type of supplement (P = 0.5262) and interaction. N2O emissions were not affected by periods (P = 0.4698), types of excreta (P = 0.8265), types of supplements (P = 0.8707) and interactions. The emissions factors N2O were not affected by periods (P = 0.4492), types of excreta (P = 0.7575), types of supplements (P = 0.7411) and interactions. It is concluded that the effect of supplementation of beef cattle in the rearing phase with RUP on NH3 and CH4 emissions is dependent on the period and type of excreta. However, no effects on N2O emission were observed. The emission factors of N2O, NH3 and CH4 from the excreta of beef cattle in the rearing phase are below the values recommended by the IPCC, overestimating the amount emitted by the activity in our conditions of breeding in a tropical climate.
Descrição
Palavras-chave
Gases de efeito estufa, Óxido nitroso, Amônia, Proteína metabolizável, Greenhouse gases, Nitrous oxide, Ammonia, Metabolizable protein