Research over the past two decades suggests one of the most influential periods in a bull’s reproductive life occurs during the first few months after birth, when endocrine signals are programming how the testes will develop for the rest of the animal’s life.
Andrea Bedford shares key takeaways from The Bovine Vet Podcast featuring John Kastelic, DVM, MS, PhD, who explained a shift in bull development focus to nutrition during the bull calf’s first months of life.
Kastelic’s research changes more than nutritional recommendations. It changes when conversations about fertility should begin and how to support endocrine development rather than maximize body weight alone in young bulls.
Source: Drovers, August 6, 2026. Link. Kastelic’s findings suggest reproductive development follows a biological timetable. Once this developmental window closes, later nutritional improvements cannot fully recover the reproductive capacity that was lost.
If you’re producing bulls you intend to be future sires, that supplemental feeding from 8 to 25 weeks has a huge impact for allowing that bull to reach his genetic potential for testicular development and sperm production.” – John Kastelic, DVM, MS, PhD
INSIGHTS: Kastelic’s results provide veterinarians and nutritionists with a good opportunity to bring value to producers. Share the article and follow up with a phone call or farm visit to improve outcomes for seed stock producers.
Image: Link.
Leave a Reply