three bars
Three Bars, pictured with Sid Vail in 1961 • Photo by Orren Mixer

In the Blood: Breeding Patterns Cheat Sheet

Many In the Blood columns feature information about breeding patterns. Hopefully this will help unravel the mystery when it comes to interpreting the lingo.

Inbreeding is the mating of horses that are more closely related than the average of the population. This includes the mating of brothers and sisters. Linebreeding is a less intense form of inbreeding that is designed to keep a higher relationship or number of genes in the pedigree of the individual someone linebreeds.

When we look at linebreeding and inbreeding in a pedigree, we are looking for patterns that indicate the generation where the common ancestor appears in the pedigree. The common ancestor is the individual we are inbreeding or linebreeding to.

The great sire Leo has a breeding pattern of 2 X 2 to Joe Reed P-3. This means that Joe Reed P-3 shows up in the second generation on both the sire and the dam side of Leo’s pedigree. This indicates that Leo was inbred to Joe Reed P-3, as it was the mating of a Joe Reed P-3 son and a daughter of Joe Reed P-3.

Based on the chart below, the 2 X 2 breeding pattern of Leo tells us that we can ESTIMATE that he carried 50% of blood (genes) to Joe Reed P-3. Each individual in the second generation contributes 25% of the genes to the individual and in this case, that is 25% plus 25%, which equals 50%.

The legendary Three Bars has a breeding pattern of 5 X 5 X 5 to Domino. This means that Domino appears three times in the fifth generation of Three Bars on both the sire and dam’s side of the pedigree. This is more of a linebreeding pattern, which is less intense than the inbreeding found in Leo.

This gives Three Bars a 9.375% of blood. To reach this conclusion, we add 3.125% to 3.125% to 3.125%, which equals 9.375%. Thus, we are ESTIMATING the number of genes Three Bars inherited from Domino.

We have found that genetics aren’t quite as simple as we once thought; other factors come into play in how genes are passed down. But for the pedigree person, it does give a measuring device for the influence of the common ancestors in the pedigree of a horse, despite the fact that it is an estimate of the actual genes carried by the individual.

Here’s a quick guide:

1st generation = 50% each
2nd generation = 25% each
3rd generation = 12.5% each
4th generation = 6.25% each
5th generation = 3.125% each
6th generation = 1.5625% each
7th generation = .78125% each
8th generation = .390625% each
9th generation = .1953125% each
10th generation = .09765625% each

For interpretive insight into the breeding patterns of superstars in the Western performance horse industry, follow the In the Blood column online.