Analysis on the Contribution of Parturition Environment Factors to Birth Weight and Gestation Period in Hanwoo

This study was designed to determine the environmental factors influencing birth weight and gestation period in Hanwoo by analyzing reproductive records from 2011 to 2023 of 370,444 cows. Initial statistical analyses revealed the average birth weight to be 27.27± 2.48 kg and the average gestation period to be 288.41±6.25 days over the study period. Variance analysis have significant impacts of calf gender on both birth weight and gestation period. Similarly, parity, calving season, mating year, and calving year showed substantial effects on birth weights and gestation period. It noted that there was the reciprocal significance between gestation period and birth weight. In detailed analysis of gestation period and birth weight, considering factors contain calving season, calving year, mating year, parity, and gender, revealed nuanced insights. Although birth weights did not significantly differ between spring and fall, they were the highest value in spring. Winter has the longest gestation periods (p<0.01). While calving years does not show significant variance in birth weight, the year 2023 showed the highest weights and longest gestation periods. Gender analysis indicated that steers exhibited both higher birth weights and longer gestation periods than cows. For mating years, year 2022 had the highest average birth weight (27.33kg), with the longest gestation periods recorded in 2011. Parity effects were notable, with the second parity showing the largest, albeit non-significant, birth weights, and the tenth parity exhibiting the longest gestation periods. Contribution analysis to variance in birth weight showed that gender was the most influential factor, followed by gestation period, calving season, calving year, and mating year, with contribution rate of 0.60%, 0.27%, 0.09%, 0.24%, and 98.64%, respectively. The model’s R-square value of 0.1327 suggests it explains approximately 13.27% of the variance in birth weights, with all variables being statistically significant (p<0.01). For gestation period, parity was the primary contributor, followed by gender, calving season, birth year, mating year, and birth weight, with contribution rate of 38.05%, 27.67%, 1.44%, 1.16%, 30.84%, and 0.83% respectively. The explanatory power for gestation period was lower, with an R-square value of 0.0221, indicating all variables were statistically significant (p<0.01).