2018 Volume 89 Issue 2 Pages 171-179
This study was conducted to examine the effect of restricted feeding on feed intake, growth performance, carcass characteristics, and feed digestibility in Japanese Black fattening steers. Eight 14-month-old Japanese Black steers were used in this study. Experimental period was 14 months (i.e., 14-28 months of age). The fattening period was divided into two stages based on the age of the steers. These stages represented the middle stage and late stage, at 14-22 and 23-28 months of age, respectively. The steers were divided into two groups. The restricted group (RG, n＝4) was fed concentrate and rice straw with total digestible nutrients at 110% of the Japanese Feeding Standard for fattening steers, expecting a daily weight gain (DG) of 0.75kg. The control group (CG, n＝4) was supplied both concentrate and rice straw ad libitum. Feed intake per metabolic body size (MBS) was significantly lower in RG than in CG during the middle stage. However, during the late stage, feed intake per MBS was higher (P<0.10) in RG than in CG. The monthly trend of feed intake per MBS in CG decreased from 21-23 months of age, which is the end of the middle stage. After 24 months of age, feed intake per MBS was slightly higher in RG than in CG (P<0.10). Feed efficiency in RG was higher than that in CG during the middle (P<0.05) and late stage (P<0.10). DG was not affected by restricted feeding in middle stage. However, during the late stage, DG was significantly higher in RG than in CG. No effect on carcass characteristics was observed under restricted feeding. During the late stage, the effect of the hot environment on dry matter (DM), organic matter (OM), and crude protein (CP) digestibility was different between CG and RG. DM and OM digestibility in RG during the hot season was significantly higher than those during the moderate season. CP digestibility in CG during the hot season was lower than that during the moderate season (P<0.05). In contrast, DM and OM digestibility in CG and CP digestibility in RG were not affected by hot environment. In addition, reduction of nitrogen retention and change in plasma total protein in RG were alleviated in the hot season. The results indicate that restricted feeding increases feed efficiency and reduce effects of hot environment on nitrogen retention.
