ABSTRACT We investigated the effects of corn grain, finely or coarsely ground, rehydrated and ensiled to 35% moisture in substitution of dry corn grain on performance of beef cattle in the feedlot. Forty non-castrated young Angus crossbred bulls with average age of 13±1.4 months and average initial body weight (BW) of 374±14 kg. The experiment was conducted in blocks by weight, and bulls were randomly assigned into four groups of five animals each in a 2 × 2 factorial scheme. The factors evaluated were particle size (finely and coarsely ground) and two grain sources (dry ground corn and rehydrated corn grain silage). The treatments were diets containing dry corn grain, finely ground (DCF; 1.86 mm); dry corn grain, coarsely ground (DCC; 3.53 mm); rehydrated and ensiled corn grain, finely ground (RCF; 1.86 mm); and rehydrated and ensiled corn grain, coarsely ground (RCC; 3.53 mm). Initial BW, final BW, average daily gain (ADG), feed efficiency, and intake of dry matter (DMI), acid detergent fiber, and metabolizable energy were not affected by treatment. Ensiling corn grain decreased DMI by 10.3% (11.6 vs. 10.4 kg/d for dry and ensiled, respectively) and increased feed efficiency by 13.3% (0.13 vs. 0.15 kg/d for dry and ensiled, respectively), but there was no effect of particle size, grain source, and their interaction on ADG. Effects of particle size and grain source were observed for fecal starch and total tract starch digestion, with evidence that treatments containing rehydrated corn diets showed greater efficiency in the utilization of dietary starch. Animals fed RCF diets showed lower fecal starch losses of 37, 55, and 75% when compared with treatments RCC, DCF, and DCC, respectively. Our results suggested that ensiled rehydrated corn grain improves feed efficiency in substitution of dry corn grain. The finely and coarsely ground of rehydrated and ensiled corn grain increases the digestibility of starch for finishing cattle in feedlot.

RESUMO. O objetivo da pesquisa foi avaliar os efeitos da reidratação do grão de milho em dois diâmetros geométricos médios (DGM = 0,55 e 1,83 mm) sobre perfil fermentativo e composição química das silagens. O experimento foi conduzido em delineamento inteiramente casualizado sendo os tratamentos: silagem de milho finamente reidratado (SMFR) e silagem de milho moído e reidratado (SMMR), com seis repetições. Os materiais foram reidratados com água objetivando níveis de umidade próximos a 350 g kg-1. Em ambas as silagens foram verificadas uma recuperação da matéria seca superior a 97%; porém sem diferença entre ambas. Houve influência do tamanho de partícula sobre a porção fibrosa, com valores inferiores observados para a SMFR. A concentração de ácido acético e lático foi maior para a SMFR, porém sem promover alterações significativas no pH da silagem. O pH foi diferente apenas na fase de exposição ao oxigênio, com valores de 4,25 e 4,38 para a SMFR e SMMR, respectivamente. Após a abertura dos silos, ambas as silagens demonstraram alta estabilidade aeróbia, acima de 90 horas, evidenciando menor atividade de espoliação e menor perda de qualidade. Concluiu-se que o DGM dos grãos de milho afetou o perfil fermentativo e nutricional da silagem.

ABSTRACT. This study evaluated the effects of the rehydration and ensiling of corn grain with two geometric mean diameters (GMD) of 0.55 and 1.83 mm obtained by the diameter of the sieved used on the fermentation characteristics and chemical composition of the silage. The experimental design was completely randomized with two treatments and six replications, as follows: rehydrated fine-corn grain silage (RFS) and rehydrated coarse-corn grain silage (RCS). Ground corn was rehydrated with water to achieve moisture levels close to 350 g kg-1. There was no effect on the dry matter recovery, though the recovery rate was high, with values greater than 97% in both silages. The particle size influenced the fiber content, with lower values in the RFS. The acetic and lactic acid concentrations were higher in the RFS, but the pH of the silages did not change. Oxygen exposure changed the pH of silages to 4.25 and 4.38 for RFS and RCS, respectively. After opening the silos, the silages showed high aerobic stability after 90 hours, which resulted in lower deterioration and lesser loss of quality. The geometric mean diameter of corn grain affects the silage fermentative profile and nutritional value.