This episode examines whether feeding additional vitamin A to cows before calving can improve the vitamin A status of their calves. Reviewing two dairy research studies, the hosts explore how late-gestation supplementation affects vitamin A levels in colostrum, milk, and newborn calves. In the first study, cows received vitamin A at levels slightly above recommended requirements, but researchers found no increase in colostrum vitamin A content and no meaningful improvement in calf blood vitamin A concentrations.
The second study supplemented cows with much larger amounts of beta-carotene, a precursor to vitamin A. While this significantly increased beta-carotene levels in colostrum and resulted in more calves having detectable beta-carotene after birth, it still failed to increase retinol, the active form of vitamin A, in calf blood samples. The findings suggest that transferring additional vitamin A from cow to calf through maternal supplementation is more difficult than many producers might expect.
The discussion reinforces that newborn calves receive very little vitamin A through placental transfer and rely heavily on colostrum as their primary source after birth. However, even feeding cows three to four times the recommended vitamin A levels produced only modest changes in calf vitamin A status.
The hosts also compare these dairy studies to previous beef cattle research, noting that very large supplementation rates may be required before measurable improvements occur in calves. As a result, simply increasing vitamin A intake in pregnant cows may not be an efficient solution for improving calf vitamin A status. The episode concludes by raising important questions about whether calves born to cows consuming stored hay during late gestation may benefit from alternative strategies, such as direct vitamin A supplementation, and emphasizes the need for additional research to better understand vitamin A requirements in modern beef production systems.
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