Effect of birth and lactation season on the growth of Korean Hanwoo calves

Abstract

South Korea has a temperate climate with four distinct seasons. However, summers are extremely hot and humid, which negatively affects industrial animal production. Hanwoo are native cattle that have traditionally been raised in the natural environment of Korea. The present study investigated the effects of birth and lactation season on the birth and weaning weights of Hanwoo calves. Data were collected from 100 local breeding farms between 2016 and 2021. A total of 56,970 (males, 29,530; females, 27,440) Hanwoo calves were classified according to sex or birth and weaning season (March-May, spring; June-August, summer; September-November, fall; and December-February, winter). The birth weight of Hanwoo calves differed according to the birth season. As such, birth weight of the summer-born calves was the lowest. Additionally, the 90-day weaning weight was positively correlated with birth weight. Interestingly, however, the 90-day weaning weight was not related to the birth season but was related to the 2-month seasonal effect during the lactation period. Furthermore, the 90-day weaning weight was the lowest during the summer lactation period. In the beef cattle industry, daily weight gain is an important economic characteristic related to feed efficiency and growth. Our findings will contribute the management of Hanwoo cattle and analysis of changes in economic characteristics due to high temperatures.

Sex ratio and conception rates of fresh/vitrified embryos at different developmental stages by ovum pick up in Hanwoo cows

“…In this study, a stable pregnancy rate of approximately 50% was observed during summer and fall, which is consistent with the findings of Hasler et al [23]. The average summer temperature in Korea is below 30 ℃, and temperatures approximately 10 ℃ lower than those used in heat stress experiments (above 40 ℃) do not significantly affect embryo transfer [55]. Moreover, during spring and winter, a conception rate of approximately 40% was observed, which was approximately 10% lower than the conception rates during summer or fall.…”

Improved pregnancy rate and sex ratio in fresh/frozen in vivo derived embryo transfer of Hanwoo (Bos taurus coreanae) cows

“…Embryo transfer in cattle can accelerate the rate of genetic improvement compared to artificial insemination, particularly through the breeding of high-value female donors [ 1 , 2 ]. In Hanwoo cattle ( Bos taurus coreanae ), embryo transfer is performed for commercial purposes to enhance the quality and quantity of beef meat, with males typically raised for fattening and females for breeding [ 3 , 4 ]. With the accelerating development in embryo transfer technologies, understanding their impact on pregnancy rates and the male-female sex ratio remains an important area of research to improve the livestock industry.…”