It is often believed that when you witness a cow in standing heat that it equals ovulation. However, ovulation generally occurs 12 - 36 hours after the beginning of standing heat. This is important to understand, especially when working with heifer-sexed semen, which generally has a shorter lifespan then conventional semen. 

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If cattle do not ovulate until 12+ hours after standing heat, why do we use it as a marker to Artificially Inseminate?

• Since most of us can't watch our cattle every second of the day, we often don't know exactly when "standing heat" first occurred. Making the timeframe a bit murky. It's also worth noting sperm cells have a significantly longer lifespan than oocytes, giving you some leeway. 

• Conventional semen is usually good for up to 36 hours in the female reproductive tract, dependent on the bull's sperm health, female's nutrition, and the reproductive tract's temperature and pH. Conventional Semen has a maturation window of 6-8 hours in the reproductive canal before making its way to the oocyte. This time delay and lifespan of the sperm is why breeding after seeing standing heat is a good indicator to A.I. Also, the fertility status of the individual bull used is a big factor in sperm viability. (thus the importance of reading a BSE!) 

• Heifer-Sex-Sorted Semen is a bit different, because it has underwent the sorting process (See this article for how they do that) it generally has a shorter lifespan in the female reproductive tract. (about 12 hours) making the correct window of when to breed a bit tighter.

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So after synching my cattle and observing standing heat, when should I Artificially Inseminate? 

• The Short Answer: Do not deviate from the protocol you selected! BUT using heat patch's and observing standing heats in your individual cattle can tell you a lot about where your female is at to achieve the best results. Click the article below to learn why! 

The University of Missouri has a great article on this one! 

Click Here to Read