The present work was developed based on three studies. The objective of the firs study was to evaluate the effects of partially replacing dry ground corn with glycerin on ruminal fermentation using a dual-flow continuous culture system. Six fermenters (1,223 i 21 ml) were used in a replicated 3x3 Latin square arrangement with three periods of 10 d each, with 7 d for diet adaptation and 3 d for sample collections. All diets contained 75% concentrate and three dietary glycerin levels (0, 15, and 30% on dry matter basis), totaling six replicates per treatment. Glycerin levels did not affect apparent digestibility of DM (PLin. = 0.13; PQuad, 0.40), OM (Pm, = 0.72; PQuad, = 0.15), NDF (PLin. = 0.38; PQuad. = 0.50) and ADF (PLin- 0.91; PQuad. = 0.18). Also, glycerin inclusion did not affect true digestibility of DM (PLin. 0.35; PQuad_ = 0.48), and OM (Pm. = 0.08; PQuad_ = 0.19). Concentrations of propionate (P 0.01) and total volatile fatty acids (P 0.05) intakes of crude protein, non-fiber carbohydrates, and total digestible nutrients. Digestibility of dry matter, organic matter, neutral detergent fiber, and total digestible nutrients increased quadratically (P 0.05). These results suggest that crude glycerin may be included in finishing beef diets at levels up to 15% without impairing performance and carcass characteristics. For the third study, five in vitro experiments were conducted to evaluate the metabolizable energy and changes on ruminal fermentation, total gas production and greenhouse gases concentration of glycerin compared to corn and starch, as well as when glycerin was added in finishing beef diets. For Exp. 1, a 24 bottles system (AnkomRF Gas Production System, Ankom technology, NY, USA) was used in 4 consecutive runs of 48 h. The treatments were three different feedstuffs: corn, glycerin, and starch. The 24 h total gas production, acetate concentration, and acetate: propionate ratio decreased (P 0.05) 24 h and 48 h total gas production, final pH, NHg-N, total VFA, propionate, and butyrate concentrations. The inclusion of glycerin linearly decreased acetate concentration (P 0.03) and acetate: propionate ratio (P = 0.04). For Exp. 3, a total of 20-serum bottles (155 mL) were used in 4 consecutive runs of 48h. The treatments were the same of Exp. 1. The CH4 concentration increased (P 0.05) on total VFA, and propionate concentration. Compared with glycerin treatment, acetate concentration (P 0.01) and acetate: propionate ratio (P = 0.01) were higher for corn and starch, whereas butyrate and valerate concentrations were higher (P = 0.01) for glycerin. For Exp. 4, a total of 25-serum bottles (155 mL) were used in 4 consecutive runs of 48h. The treatments were the same of Exp. 2. The glycerin inclusion did not affect (P > 0.05) the concentrations of CH4, Co2, final pH, and total VFA, propionate, butyrate, and acetate: propionate ratio. A linear decrease of acetate concentration (P = 0.04) was observed due to inclusion of glycerin in the diets. For Exp. 5, two systems of four 4-L digestion vessels (Daisyll system, Ankom technology, NY, USA) were used in two consecutive runs of 48 h. The treatments were: orchard hay (0.4 g/bag), corn (0.4 g/bag), orchard hay (0.4 g/bag) + glycerin (0.2 g/bag) and corn (0.4 g/bag) + glycerin (0.2 g/bag). Orchard hay with glycerin inclusion presented lowest (P 0.05) between corn with or without glycerin. We concluded that, under these experimental conditions, glycerin contributed more to the enhancement of methanogenesis than carbohydrates, but effectively replaced dietary corn as energy source at up to 30og/kg of the diet.O presente trabalho foi desenvolvido baseado em trés estudos. 0 obj etivo do primeiro estudo foi avaliar os efeitos da substituioao parcial do milho por glicerina sobre a fermentaoao ruminal utilizando urn sistema de cultura continua de fluxo duplo. Seis fermentadores (1,223 i 21 ml) foram utilizados em urn delineamento em quadrado latino 3X3 replicado, corn trés periodos de 10 d cada, 7 d para adaptaoao a dieta e 3 d para coletas de amostras. Todas as dietas continham 75% de concentrado e trés niveis de glicerina na dieta (0, 15, e 30% com base na matéria seca), totalizando seis repetiooes por tratamento. Os niveis de glicerina nao afetaram a digestibilidade aparente da MS (PLm = 0,13; PQuad, = 0,40), MO (PLin. = 0,72; PQuad_ = 0,15), FDN (PLin, = 0,38; PQuad, = 0,50) e FDA (PUD, = 0,91; Pouad. = 0,18). Além disso, a inclusao de glicerina nao afetou a digestibilidade verdadeira da MS (PLin, = 0,35; PQuad_ = 0,48), e MO (Pm, = 0,08; PQuad, = 0,19). As concentraooes de propionato de (P 0,01) e acidos graxos volateis totais (P 0,05) 0 consumo de proteina bruta, carboidratos nao fibrosos e nutrientes digestiveis totais. As digestibilidades da matéria seca, matéria organica, fibra em detergente neutro e nutrientes digestiveis totais aumentaram de forma quadratica (P 0,05). Estes resultados sugerem que o glicerina bruto pode ser incluido em dietas de acabamento de bovinos de corte em niveis de até 15%, sem prejudicar o desempenho e as caracteristicas de carcaca. Para 0 terceiro estudo, cinco experimentos in vitro foram conduzidos para avaliar a energia metabolizavel e as mudancas na fermentacao ruminal, producao total de gases e concentracao de gases do efeito estufa da glicerina, comparada ao milho e ao amido, bem como sua inclusao em dietas de terminacao para gado de corte. Para 0 Exp. 1, um sistema de 24 garrafas (AnkomRF Gas Production System, Ankom technology, NY, USA) foi usado em 4 corridas consecutivas de 48 h. Os tratamentos foram trés diferentes alimentos: milho, glicerina e amido. A producao total de gases as 24 h, a concentracao de acetato e a relacao acetato: propionato diminuiu (P 0,05) as producoes de gases as 24 e 48 h, 0 pH final, N-NH3, AGV total, e as concentracoes de propionato e butirato. A inclusao de glicerina diminuiu linearmente a concentracao de acetato (P = 0,03) e a relacao acetato: propionato (P = 0,04). Para 0 Exp. 4, um total de 25 garrafas (155ml) foram usadas em 4 corridas consecutivas de 48 h. Os tratamentos foram os mesmos do Exp. 3. A inclusao de glicerina nao afetou (P > 0,05) as concentracoes de CH4, Co2, AGV totais, propionato, butirato, relacao acetato: propionato e pH final. Foi observada diminuicao linear (P = 0,04) na concentracao de acetato deVido a inclusao de glicerina nas dietas. Para 0 Exp. 5, dois sistemas de quatro vasos de digestao de 4 L (Daisyll system, Ankom technology, NY, USA) foram usados em duas corridas consecutivas de 48 h. Os tratamentos foram: feno de orchard (0,4 g/saco), milho (0,4 g/saco), feno de orchard (0,4 g/saco) + glicerina (0,2 g/saco) e milho (0,4 g/saco) + glicerina (0,2 g/saco). O feno de orchard com glicerina apresentou a menor (P 0,01) digestibilidade in Vitro da MS, seguido pelo feno de orchard sem adicao de glicerina e pelos tratamentos com milho. A digestibilidade in Vitro da MS nao diferiu (P > 0,05) entre os tratamentos com milho sem on com adicao de glicerina. Como conclusao, sob essas condicoes experimentais, a glicerina contribuiu mais para o aumento da metanogenese do que carboidratos, mas efetivamente substituiu parcialmente o milho como fonte de energia em dietas para bovinos de corte.Conselho Nacional de Desenvolvimento Científico e Tecnológic
