Microbial populations and fermentation profile in tropical grass silages and performance of beef cattle fed diets containing mombaça grass silages / Populações microbianas e perfil fermentativo em silagens de capins tropicais e desempenho de bovinos de corte alimentados com dietas contendo silagens de capim-mombaça

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This study consisted of five experiments. The first evaluated the microbial populations, fermentation profile and chemical composition of silages of signal grass at different regrowth ages (30, 40, 50, 60 and 70 days) in six fermentation periods (1, 3, 7, 14, 28 and 56 days). There was increase in lactic acid bacteria (LAB) and decrease in enterobacteria (ENT) with regrowth age of signal grass. Maximum values for LAB (8.69 log UFC/g) were recorded on the seventh day of fermentation, whereas ENT reached maximum growth (7.89 log UFC/g) on the first day of fermentation. Levels of lactic acid increased, while the levels of acetic and butyric acids and ammonium nitrogen: total nitrogen (N-NH3) ratio decreased linearly (P<0.05) with regrowth age. The pH decreased exponentially (P<0.05) with period of fermentation. Levels of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent insoluble nitrogen (ADIN) increased linearly (P<0.05) with regrowth age, while the levels of crude protein (CP) decreased linearly (P<0.05). Over the fermentation period, linear increases were found (P<0.05) for the levels of lactic, acetic and butyric acids and NNH3, while the levels of MS, NDF, CP and ADIN decreased linearly (P<0.05). Lactobacillus plantarum was the predominant Lactobacillus species in signal grass. The second experiment evaluated the microbial populations, pH and ammonium nitrogen: total nitrogen (N-NH3) ratio of moçamba grass silages at different regrowth ages (35, 45, 55 and 65 days), in six fermentation periods (1, 3, 7, 14, 28 and 56 days). There was increase in LAB populations and decrease in ENT populations and molds and yeasts (MY) with regrowth age of mombaça grass. The maximum LAB population was found on the third day (plants harvested at 55 and 65 days of regrowth) and on the seventh day (plants harvested at 35 and 45 days of regrowth). ENT and MY populations reached maximum growth on the first day of fermentation. Lactobacillus plantarum was the predominant species in the mombaça grass. There were decrease and linear increase (P<0.05) of N-NH3 level with regrowth age and fermentation period respectively. The pH decreased exponentially (P<0.05) with the fermentation period and with regrowth age. The third experiment evaluated the fermentation profile, dry matter recovery and the chemical composition of silages treated with microbial inoculant from experiment 2. There was linear and exponential reduction (P<0.05) in N-NH3 levels and pH respectively, with regrowth age. The lactic acid level increased (P<0.05), while acetic and butyric acids decreased (P<0.05) with regrowth age. The levels of MS, NDF, ADF and ADIN increased, while the level of CP decreased linearly (P<0.05) with regrowth age. Gas and effluent losses decreased, while dry matter recovery increased linearly (P<0.05), with regrowth age. The inoculant reduced (P<0.05) pH, levels of N-NH3, acetic and butyric acids, gas losses and increased (P<0.05) levels of MS and CP and dry matter recovery of the silages. The fourth experiment evaluated consumption, total and partial nutrient digestibility and ruminal parameters in rumen-and-abomasum-fistulated beef cattle fed diets containing mombaça grass silages treated with microbial inoculants. None of the variables was found to be influenced (P>0.05) by the experimental diets. Mean consumptions of MS, CP, NDF and total digestible nutrients (TDN) were recorded at 7.28, 0.85, 4.01 and 4.22 kg/day, respectively. The total, ruminal and intestinal apparent digestibilities for MS were 52.13, 61.76 and 38.23%, respectively. Mean values for passage rate were 4.09, 3.91 and 4.21%/h for the diets containing silages without inoculant and inoculated with Sill All C4 and Master Silo respectively. The fifth experiment evaluated the productive performance of beef cattle fed the same diets of the fourth experiment. Once more, none of the variables was influenced (P>0.05) by the experimental diets. Mean values for consumption of MS, CP, NDF and TDN were 8.08, 0.95, 3.82 and 6.24 kg/day respectively. Mean values for weight gain and feed conversion of 0.78 and 11.11 kg/day, respectively, were also recorded.

ASSUNTO(S)

fermentation fermentação zootecnia bactéria lática lactic bacteria valor nutritivo nutrition value

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