Effects of Grazing or Exercise in the Middle of the Fattening Period on the Growth and Carcass Traits of Japanese Shorthorn Steers

Abstract

The effects of grazing or exercise in the middle of the fattening period on the growth and carcass traits of Japanese Shorthorn (JS) steers were investigated. JS steers were assigned to three groups: G (grazed), E (exercised), and B (barn-kept cattle). In the treatment period, group G was kept in the pasture, while groups B and E were confined to individual pens indoors at night, and stayed in a paddock during the day. In addition, group E was made to walk 4.0 km in the evening, five days a week. After the treatment, all the steers were housed and kept the same way as group B. The steers were slaughtered at 24 - 25 months of age. Group G exhibited a lower average daily gain (ADG) than groups B and E during the treatment period. Conversely, group G showed significantly higher ADG than the other two groups during the post-treatment period. Carcass weight for group G was smaller than those for the non-grazed counterparts. Groups G and E exhibited larger (p < 0.05) proportions of liver and spleen weights to live weight than those of group B. Group G also showed larger proportions of biceps femoris and quadriceps femoris muscles to carcass weight than those of group B. Group G exhibited a smaller ratio of fat and a larger ratio of muscle in the transverse section of the sixth rib, respectively, than those of group B. These results suggest that grazing or exercise in the middle of the fattening period affect growth in the late fattening period, and the carcass traits of JS steers even after being kept indoors for more than half a year.