Every day on a farm is a series of decisions. The challenge is knowing when new evidence is strong enough to change the way we have always done things.

A question worth discussing

Many FARMGATE Notes are philosophical. But every once in a while, a research paper comes along that is worth putting on the table—not because it gives us all the answers, but because it asks a question worth discussing.

The question was remarkably simple: should we double the GnRH (Factrel/Fertiline) dose at the start of the Breeding Ovsynch portion of a Double OvSynch breeding program?

Read the Journal of Dairy Science paper shared with the original note

What the study found

Researchers followed 6,621 lactating dairy cows on four commercial dairies, comparing the traditional 100 µg (2 mL) dose with a 200 µg (4 mL) dose of GnRH at the first injection of the Breeding Ovsynch protocol.

Overall pregnancy to first service increased from 48.6% to 51.8%. A few additional pregnancies per hundred breedings can have a meaningful impact on a dairy.

  • First-lactation conception rates were essentially unchanged: 51.8% versus 52.8%.
  • In mature cows, pregnancy to first service increased from 45.4% to 50.7%.
  • Overall ovulation at the start of the protocol increased from 70.8% to 83.0%.

Why the answer is not quite that simple

Many first-lactation animals in the study were bred with sexed dairy semen, while many mature cows received conventional beef semen. The authors could not fully separate the effects of age and semen selection because semen use was not consistent across all four herds.

When the researchers looked only at cows bred with sexed semen, the advantage of the higher GnRH dose largely disappeared. The improvement was seen primarily in cows bred with conventional semen.

The pregnancy outcomes included more than 6,600 cows, but the ovulation work involved 505 cows from one herd, and the detailed luteinizing-hormone measurements came from 18 cows. That does not make the study wrong; it reminds us that every paper has strengths and limitations.

From research to the herd

Research is not meant to replace experience. It is meant to challenge it. Good science does not always tell us what to do; more often, it helps us ask better questions.

  • Would this protocol improve pregnancy rates in your herd?
  • Would it be most beneficial in mature cows?
  • Would the additional drug cost be returned through improved reproductive performance?
  • Is your herd already achieving excellent conception rates with its current protocol?

Veterinary medicine sits at the intersection of science and practicality. Our responsibility is to filter published research through experience, understand the unique challenges of each herd, and decide whether it fits.

Sometimes the answer is yes. Sometimes it is not yet. And sometimes the most valuable thing a paper gives us is not a new protocol at all—it is a better question.

As promised.
Less Noise. Better Decisions.
— Jon