Understanding the Inbreeding Coefficient

The Inbreeding insight card estimates how closely related an animal’s sire and dam are by calculating its coefficient of inbreeding from the recorded ancestor tree. It also lists the shared ancestors that drive the number.

What the Coefficient Means

The coefficient of inbreeding is shown as a percentage. In plain terms, it estimates the chance that the two copies of a gene an animal carries came from the same ancestor on both the sire’s and the dam’s side. A higher percentage means the parents share more common ancestry.

Cattle360 uses Wright’s coefficient of inbreeding: for every ancestor that appears on both the sire’s and the dam’s side of the tree, it adds a contribution based on how many generations back that ancestor sits on each side. The closer and the more often a shared ancestor appears, the more it adds.

Risk Levels

Cattle360 buckets the coefficient into four levels for a quick read:

For reference, the offspring of a half-sibling or grandparent–grandcalf mating lands around 12.5%, and full-sibling or parent–offspring matings land around 25%.

Shared Ancestors

Below the figure, the card lists each ancestor that appears on both parent lines. For every shared ancestor you’ll see:

• Sire +N / dam +N — how many generations back the ancestor sits on the sire’s side and on the dam’s side.
• Contribution % — how much that single ancestor adds to the overall coefficient.

If no ancestor appears on both sides, the card shows “No common ancestors found in the available pedigree,” and the coefficient is 0%.

Generations Analyzed

The caption notes how many generations of ancestry were included in the calculation. Because the pedigree tab looks back up to three generations, the coefficient reflects the ancestry Cattle360 can see — it is a lower bound. Relatedness hidden further back than your recorded tree isn’t counted, so the true figure could be higher.

Important Notes

• Inbreeding is only calculated when both a sire and a dam are recorded. With one parent missing, there are no two lines to compare and the coefficient stays at 0%.
• Deeper, more complete pedigrees give better estimates. Adding grandparents and great-grandparents lets Cattle360 detect shared ancestry it would otherwise miss.
• The figure is an estimate, not a substitute for genetic testing. Use it as a screening tool when planning matings.

Tips

• Check inbreeding before you breed, not after. The Preview a mating tool projects the coefficient for a calf before the pairing is made.
• Watch the shared-ancestor list, not just the headline number. A single ancestor dominating the contribution can guide which line to breed away from.