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IMPACTO AMBIENTAL DA PRODUÇÃO DE SILAGENS: REVISÃO DA LITERATURA E AVALIAÇÃO EXPERIMENTAL EM SILOS LABORATORIAIS.

CAMILLA MACIEL DE SOUZA.
Tese em Português | VETTESES | ID: vtt-203613

Resumo

A ensilagem é a principal técnica de conservação de forragens utilizada para suprir a demanda de alimentos volumosos na nutrição de ruminantes. Porém, a extensão do impacto ambiental causado por essa prática ainda é pouco estudada. Nesta dissertação, objetivou-se fornecer uma visão geral sobre o impacto ambiental da produção de silagens, através de revisão da literatura; e contribuir especificamente com a avaliação de perdas fermentativas em silos laboratoriais, através da realização de quatro ensaios experimentais. Dentre os focos de impacto do processo de ensilagem, estão: uso da terra, sistema de plantio, escolha da espécie forrageira, adubação, uso de herbicidas e pesticidas, uso de maquinário, momento de colheita, teor de matéria seca na ensilagem, tipo de silo e vedação, perdas fermentativas e produção de efluentes. Nos ensaios experimentais, quatro espécies forrageiras (capim-elefante, azevém, cana-de-açúcar e milho) tratadas com aditivos químicos e biológicos foram armazenadas em silos laboratoriais, equipados com dispositivos coletores de gás e de efluente, por cerca de dois meses. O volume de gás produzido foi medido diretamente durante a fermentação, e comparado com a metodologia tradicional de avaliação de perdas por gravimetria. A composição bromatológica, as contagens microbianas, o perfil fermentativo e a estabilidade aeróbia das silagens também foram avaliados. As perdas fermentativas foram baixas nas silagens de capim-elefante, azevém e milho, e expressivas nas silagens de cana-de-açúcar. A correlação entre a metodologia proposta e a metodologia atual de avaliação de perdas foi variável em cada ensaio. No ensaio da cana-de-açúcar, todas as metodologias avaliadas estiveram alinhadas. O efeito benéfico dos aditivos em reduzir as perdas fermentativas foi observado nas silagens de azevém e cana-de-açúcar, e menos evidentes ou ausentes nas silagens de capim-elefante e milho, respectivamente. Boas práticas de manejo devem ser observadas para reduzir o impacto ambiental da produção de silagens. O uso de aditivos com essa finalidade necessita de análise cuidadosa da relação custo-benefício e pode ser considerado como um ajuste final, desde que as condições básicas de manejo sejam atendidas.
Silage making is the main forage conservation technique to supply the roughage demand in ruminant nutrition. However, the extension of the environmental impact caused by this process is still unknown. We aimed to provide an overview on environmental impact of silage production based on published data; and access the fermentation losses in lab silos, in four experimental trials. The sources of environmental impact comprise: land usage, tillage system, forage species, soil fertilization, use of pesticides and herbicides, machinery, maturity at harvesting, dry matter content at ensiling, type of silo and sealing, fermentation losses and effluent production. In the trials, four forage species (elephant-grass, ryegrass, sugarcane and corn) treated with different additives were ensiled in lab silos, equipped with gas and effluent collecting devices. Silos were stored for approximately two months. Volume of gas produced during the fermentation was directly measured and compared to gravimetric methodologies of dry matter losses. Silage chemical composition, microbial counts, fermentation profile and aerobic stability were also measured. Fermentation losses were low in all trials, except for sugarcane. The correlation between the proposed and current methodology for measuring gas production varied among trials. In the sugarcane trial, all methodologies were in line with one another. The effect of additives on mitigating fermentation losses was present in ryegrass and sugarcane silages and less evident or absent in elephant-grass and corn silages, respectively. Good management practices must be adopted to reduce environmental impact of silage production. The recommendation of additives for this purpose requires careful cost-benefit analyses and might be considered as a fine tuning improving, once the basic management techniques were met. Key words: Silage making is the main forage conservation technique to supply the roughage demand in ruminant nutrition. However, the extension of the environmental impact caused by this process is still unknown. We aimed to provide an overview on environmental impact of silage production based on published data; and access the fermentation losses in lab silos, in four experimental trials. The sources of environmental impact comprise: land usage, tillage system, forage species, soil fertilization, use of pesticides and herbicides, machinery, maturity at harvesting, dry matter content at ensiling, type of silo and sealing, fermentation losses and effluent production. In the trials, four forage species (elephant-grass, ryegrass, sugarcane and corn) treated with different additives were ensiled in lab silos, equipped with gas and effluent collecting devices. Silos were stored for approximately two months. Volume of gas produced during the fermentation was directly measured and compared to gravimetric methodologies of dry matter losses. Silage chemical composition, microbial counts, fermentation profile and aerobic stability were also measured. Fermentation losses were low in all trials, except for sugarcane. The correlation between the proposed and current methodology for measuring gas production varied among trials. In the sugarcane trial, all methodologies were in line with one another. The effect of additives on mitigating fermentation losses was present in ryegrass and sugarcane silages and less evident or absent in elephant-grass and corn silages, respectively. Good management practices must be adopted to reduce environmental impact of silage production. The recommendation of additives for this purpose requires careful cost-benefit analyses and might be considered as a fine tuning improving, once the basic management techniques were met.
Biblioteca responsável: BR68.1