Joint research involving graduate student Yutaka Taguchi, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Assistant Professor Dr. Yudai Inabu and Associate Professor Dr. Hideyuki Takahashi of the Graduate School of Agriculture, together with Mirai Global Farm K.K., Itoham Foods Inc., Nosan Corporation, RIKEN, Japan Eco-science Co. Ltd., and Graduate School of Chiba University, has found that feeding high volumes of milk replacer to female Japanese black calves may reduce the age at which they first give birth. The finding was published in Animal Science Journal.
Beef farmers are facing the problem of high calf prices as calf numbers dwindle. Solving the problem will require cows to increase their lifetime calf production. This in turn requires earlier breeding maturity, and therefore the physical attributes to enable artificial insemination (AI) at a younger age. Taguchi and his colleagues turned to the potential for improving the growth of heifers (particularly in height) by feeding them high volumes of milk replacers during suckling. They believed that a plentiful supply of replacers could help the heifers to reach breeding age faster. However, the lack of a standardized plan for milk replacer feeding meant that the impact on body growth and reproductive outcomes was not clear.
To address this problem, they trialed three different milk replacer feeding plans in 51 Japanese black heifers, starting at three days of age, and looked at growth and reproductive outcomes. The trial found that AI could begin when they reached a body weight of at least 270kg, and a height of at least 116cm. Of the 51 heifers in the trial, at least 70% achieved the physical condition required for AI by 10 months of age, with the average age of first birth across the 51 heifers at 22.1 months, more than two months shorter than the Japanese national average in 2020 of 24.5 months. A comparison of the age of first birth among the three different milk replacer feeding plans found that the most effective plan resulted in first births at 21.5 months. This implies that plentiful milk replacer feeding could reduce the national average first calving by three months, without any issues for the newborn calves.
The average age at first birth was earlier than the value targeted by the Ministry of Agriculture, Forestry, and Fisheries of 23.5 months, so this will contribute to the development of early fertilization technologies in the livestock industry. On the other hand, it was found that feeding of milk replacers above a certain volume led to energy diverted to growth rather than reproductive preparation, leading to a longer lag between initial AI and pregnancy.