This study was conducted to improve growth performance of Hanwoo heifer and to produce high quality of meat with dietary means during growing and early fattening period. Particularly, additional energy diet to relieve estrus stress was main purpose in this study. The results of in vitro rumen fermentation indicated that there was no negative effect by additional energy diet as treatments. In the feeding trial, twenty Hanwoo heifers(average 10 months age) were allocated and distributed into two treatments in randomized block design based on body weight. There were three growth stages such as growing, early fattening and late fattening periods in this feeding program, respectively. In growing stage, there were two treatments consisting of only total mixed ration(TMR) as a control and TMR with additional energy treatment. The experimental diets were fed twice a day, and water and mineral were freely accessed. In additional energy treatment, 500 g of concentrate diet was fed daily to relieve estrus stress due to obese with high energy intake. Not outstandingly differences were found across the treatments during entiretrial period. While, unexpectedly greater feed conversion ratio in treatment compared to the control was found during late fattening period. It seems that the blood cortisol decreased with addition energy supplementation compared with the control during trail period. Carcass characteristics including carcass weight, back fat thickness, marbling score, meat color, fat color, maturity and texture were not significantly different each other. Rib-eye area, however, was greater in the control compared to the treatment(p<0.05). In addition, it appears that yield index was tended to be greater in the control. In conclusion, it is suggested that additional energy supplementation to Hanwoo heifer could get a potential in improving meat quality and relieving estrus stress.

ABSTRACT
 Introduction
 Materials and Methods
  1 In vitro rumen fermentation
  2 Feeding trial
  3 Statistical analysis
 Results and Discussion
  1 In vitro rumen fermentation parameters
  2 Growth Performance of Hanwoo heifers
  3 Carcass characteristics
 References

• Joung Yong Kim(Department of Animal Science, Chonbuk National University)
• Seongjin Oh(Department of Animal Science, Chonbuk National University)
• Chaehwa Ryu(Department of Animal Science, Chonbuk National University)
• A-leum Lee(Department of Animal Science, Chonbuk National University)
• Sangbuem Cho(Department of Animal Science, Chonbuk National University)
• Nag-Jin Choi(Department of Animal Science, Chonbuk National University) Corresponding author