Androgenization of Cows as Aids for Estrous Detection and Influence of Biostimulation on Postpartum Reproduction

Abstract

Androgenized females have been well established as aids for detection of estrus in beef and dairy herds and offer several advantages in assisting humans in finding cows in estrus. Androgenized females have been observed to cause increased mounting of estrous cows and reduced mounting of non-estrous cows. Further, they have allowed for identification of more cows in estrus than human observation alone. Biostimulation was a term coined to describe the stimulatory (positive) effects of a male on estrus, ovulation or pregnancy. In cattle, biostimulatory effects were first inferred by producers with well-fed cows on year-round natural mating breeding programs who observed cows returning to estrus earlier postpartum than expected. Studies where natural mating showed advantages over artificial insemination also implied a biostimulatory effect for males. Well controlled studies provided evidence that exposure of cows to sterile bulls induced earlier return to estrus post partum than was observed in unexposed cows. Additionally, placement of androgenized females with postpartum cows also shortened postpartum intervals to first estrus, similar to results obtained with exposure to sterile bulls.