Abstract
The present study was conducted to investigate the relationships between neutral detergent fiber (NDF) intake and chewing time in fattening Japanese Black steers. In experiment 1, 18 steers were observed at the ages of 12 and 15 months. The steers were fed 5.2, 7.8 kg of concentrate and 3.1, 1.5 kg of roughage on a dry matter basis at the age of 12, 15months, respectively. In experiment 2, 15 steers were observed at the ages of 20, 25 and 28 months. The steers were divided into three groups; six steers were fed 5.1-5.3 kg of concentrate A (consisting of 50% ground corn grain) and 3.1-5.4 kg of corn silage (ConA･CS group), six steers were fed 4.8-5.1 kg of concentrate B (consisting of 40% ground brown rice) and 3.3- 5.7 kg of corn silage (ConB･CS group), and three steers were fed 8.5-8.8 kg of concentrate A and 1.0-1.6 kg of wheat straw (control group) at each observation period, respectively. In experiment 1, the NDF intakes from forage (FNDFI), the ratios of FNDFI to dry matter intake (DMI) and the chewing times of steers at the ages of 15 months decreased as the increase of the concentrate intake. In experiment 2, the FNDFIs were 1.6, 1.6, 0.7kg/day, the ratios of FNDFI to DMI were 17.5, 17.2 and 7.6%, the chewing times were 386, 436 289 minutes/day, and the RVIs were 60, 62, 46 minutes/kgDM, respectively, in the ConA･CS group, ConB･CS group and control group. The correlation coefficients between chewing time and the ratio of NDFI to DMI, and between chewing time and the ratio of FNDFI to DMI, were 0.28 and 0.51, respectively. These results indicate that the FNDFI and the ratio of FNDFI to DMI affect chewing time and RVI in the diets of fattening Wagyu steers
