Abstract #T93

# T93
Estimation of genetic parameters for calving ease of Holstein cattle in Korea.
Mahboob Alam1, Kwang Hyeon Cho*1, Tae Jeong Choi1, Chung Il Cho1, Yun Ho Choy1, 1National Institute of Animal Science, Rural Development Administration, Cheonan-si, Chungcheongnam-do, Republic of Korea.

Calving ease (CE) is a complex reproductive trait of economic importance for dairy cattle. This study was aimed to estimate the genetic parameters of CE for Holsteins in Korea. A total of 978,674 records of CE, collected from 1992 to 2014, from first 5 parities of Holstein cows were analyzed. Age of cows at first 5 parities were ranged within 18–42 mo, 30–54 mo, 42–66 mo, 54–78 mo, and 66–90 mo, respectively. Calving ease was recorded as ordered categories ranged from 1 to 5, indicating 1 = normal (not assisted), 2 = moderate assistance (extraction by 1 person), 3 = moderate assistance (extraction by 2/3 persons), 4 = difficult (extraction by > 3 persons), and 5 = surgical assistance calving. All CE categories were converted to a continuous scale through Snell score transformation procedure. The derived Snell scores for all parities were 0.01, 3.92, 6.288, 7.485, and 8.825 for category 1 through 5, respectively. A single trait sire-maternal grandsire model (S-MGS) was considered for ANOVA and covariance components from each parity cows using ASREML 3.0 software package. Age at calving was fitted as fixed covariate, and herd-year-season, sire and maternal grandsires of the recorded cows were fitted as random effects in the S-MGS model. Estimated direct heritabilities for parity 1 through 5 were 0.06 ± 0.01, 0.08 ± 0.01, 0.10 ± 0.01, 0.07 ± 0.01, and 0.06 ± 0.02, respectively. Maternal heritabilities from the models were 0.02 ± 0.01, 0.04 ± 0.02, 0.03 ± 0.01, 0.01 ± 0.01, and 0.04 ± 0.01, respectively. Genetic correlations between direct and maternal genetic components were moderately to strongly negative for first 5 parities, such as −0.51 ± 0.15, −0.50 ± 0.16, −0.89 ± 0.10, −0.97 ± 0.30, and −0.81 ± 0.17, respectively. This study being the first report on CE of Korean Holsteins, we expect that the estimated genetic parameters derived in the study would be valuable for their calving ease improvement.

Key Words: calving ease, genetic parameter, Holstein cattle