Interpretive Summary: Dam parity affects fetal growth, placental size, and neonatal metabolism in spring-born beef calves

By: Natalie B Duncan, Katy S Stoecklein, Andrew P Foote, Allison M Meyer

Approximately two-thirds of beef calf deaths prior to weaning occur within the first 3 wk after birth. The goal to have heifers produce their first calf by 2 yr of age likely contributes to factors that limit nutrients available for fetuses and calves immediately after birth. However, little is known about differences in heifers (first parity) and cows (later parities) regarding factors affecting calf resilience, such as fetal growth and calf metabolism shortly after birth. Our data show that calves born to first-parity heifers had altered nutrient availability, demonstrated through smaller placentas, lower birth weights, and altered metabolites in early life. Although calves had similar vigor and ability to maintain body temperature, calves born to first-parity heifers had to mobilize more energy and had lower insulin during the first 3 d post-birth. Calves born to first-parity heifers had greater indicators of stress during the first 72 h of life not associated with calving difficulties. Overall, these effects may have increased morbidity and mortality of calves born to first-parity heifers if they were in a less intensively-managed system. Better understanding of challenges faced by calves born to first-parity dams provides opportunities for their improved management.