This study evaluated genetic parameters of direct and maternal effects for calving ease in Hanwoo. A total of 2,102 records for calving ease were collected from 2018 to 2020 from the Hanwoo Genetic Improvement Center in Korea. The calving ease score was rated from 1 to 4 (1=unassisted delivery, 2=assisted easy calving, 3=assisted difficult calving, 4=mechanical or caesarean section) as categorical data, and the data were converted using a truncated normal distribution for linear model analysis. To evaluate the genetic parameters, the birth year-season of calving, the sex of the calf, parity, and the age of the dam at calving were considered as fixed effects, and genetic and maternal effects were considered random effects. The genetic parameters were evaluated using the program BLUPF90. The calving ease scores for male calves, first parity cows, and currently calving cows were much higher than for females, later parities, and past calving cows. The direct genetic variance (0.0164) was higher than the maternal genetic variance (0.0018), and the estimated heritabilities of the direct and maternal effects were 0.055 and 0.006, respectively. The parameters determined here should help with the genetic evaluation of calving ease in Hanwoo.

ABSTRACT
Ⅰ. 서론
Ⅱ. 재료 및 방법
    1. 공시재료
    2. 자료변환
    3. 환경요인 효과
    4. 유전모수 추정
Ⅲ. 결과 및 고찰
Ⅳ. 요약
Ⅴ. 참고문헌

• 김대중(농협경제지주 한우개량사업소) | Dae Jung Kim (Hanwoo Genetic Improvement Center, NongHyup Agribusiness Group Inc)
• 원정일(국립축산과학원 한우연구소) | Jeong Il Won (Hanwoo Research Institute, National Institute of Animal Science, R.D.A.)
• 조충일(농협경제지주 한우개량사업소) | Chung Il Cho (Hanwoo Genetic Improvement Center, NongHyup Agribusiness Group Inc) Corresponding author