For those of us that feel math is not our strong suit, there is a certain mystique regarding the calculation of breed percentages in crossbreeds.  It is actually not as complicated as it might appear.  

First, let's keep it simple by considering the breeding of one full blood (100%) Myotonic to other goats of various percentages of the Myotonic breed so we get a general idea before we start looking at more complicated crosses.

In the examples that follow, the sire will always be a 100% Myotonic buck and we won’t worry about what other breed is involved at this time.

Follow these steps:

1. Add the two percentages together
2. Divide by two

Here are some examples:

1. Bred to a doe that is 25%, or ¼ Myotonic:  100% plus 25%=125 divided by 2 equals 62.5%, or equivalent to 5/8 Myotonic

2. Bred to a doe that is 50%, or ½ Myotonic:  100% plus 50%= 150 divided by 2 equals 75%, or equivalent to ¾ Myotonic

3. Bred to a doe that is 75%, or ¾ Myotonic:  100% plus 75% =175 divided by 2 equals 87.5%, or equivalent to 7/8 Myotonic

4. Bred to a doe that is 87.5% or 7/8 Myotonic:  100% plus 87.5%=187.5 divided by 2 equals 93.75%, or equivalent to 15/16 Myotonic

5. Bred to a doe that is 93.75%, or 15/16 Myotonic:  100% plus 93.75%=193.75 divided by 2 equals 96.875%, or equivalent to 31/32 Myotonic

The above samples were simplified by having only parent be a mixture.  What do you do if it is not quite so "cut & dried"?  If both parents are crossbreeds, it still is relatively simple to calculate if you follow these steps:

1. Convert the breed percentages of both sire and dam to eighths.
2. Divide the percentages in half.
3. Add the percentages of like breeds together to find the resulting offspring.

Example:

The sire is ¾ Myotonic and ¼ Boer.  The dam is ¾ Boer and ¼ Myotonic.  Follow the steps listed above.

1. Sire converts to 6/8 Myotonic and 2/8 Boer.  Dam is 6/8 Boer and 2/8 Myotonic.

2. For the sire, division results in 3/8 Myotonic and 1/8 Boer. For the dam, the result is 3/8 Boer and 1/8 Myotonic.

3. Total is 4/8 Myotonic and 4/8 Boer. If you reduce the fractions, the end result is an offspring that is ½ Myotonic and ½ Boer. (50% Myotonic and 50% Boer)

Try another one:

The sire is ½ Myotonic and ½ Boer. The dam is ¾ Myotonic and ¼ Boer.

1. Sire converts to 4/8 Myotonic and 4/8 Boer.  The dam is 6/8 Myotonic and 2/8 Boer.

2. For the sire, division results in 2/8 Myotonic and 2/8 Boer.  For the dam, the result is 3/8 Myotonic and 1/8 Boer.

3. Total is 5/8 Myotonic and 3/8 Boer. (62.5% Myotonic and 37.5% Boer)

The third scenario, while it looks complicated, still uses the same calculations to obtain the percent of crossbreeding.  

Let’s work through it:

The sire is ¾ Boer and ¼ Spanish.  The dam is ½ Pygmy and ½ Boer.

1. The sire converts to 6/8 Boer and 2/8 Spanish.  The dam converts to 4/8 Pygmy and 4/8 Boer.

2. For the sire, division results in 3/8 Boer and 1/8 Spanish.  For the dam, the result is 2/8 Pygmy and 2/8 Boer.

3. Total is 5/8 Boer, 1/8 Spanish and 2/8 (or ¼) Pygmy (62.5% Boer, 12.5% Spanish and 25% Pygmy)

Test your knowledge:

The sire is ½ Myotonic, ¼ Pygmy and ¼ Boer.  The dam is ¼ Myotonic and ¾ Nubian.

1. The sire converts to 4/8 Myotonic, 2/8 Pygmy and 2/8 Boer.  The dam converts to 2/8 Myotonic and 6/8 Nubian.

2. For the sire, division results in 2/8 Myotonic, 1/8 Pygmy and 1/8 Boer.  For the dam, the result is 1/8 Myotonic and 3/8 Nubian.

3. Total is 3/8 Myotonic, 1/8 Pygmy, 1/8 Boer and 3/8 Nubian.  (37.5% Myotonic, 12.5% Pygmy, 12.5% Boer and 37.5% Nubian) WOW!  What would this critter look like?

Here’s one more example to make sure you really have it:

The sire is ½ Myotonic and ½ Pygmy.  The dam is ¼ Myotonic and ¾ Boer.

1. The sire converts to 4/8 Myotonic and 4/8 Pygmy.  The dam converts to 2/8 Myotonic and 6/8 Boer.

2. For the sire, division results in 2/8 Myotonic and 2/8 Pygmy.  For the dam, the result is 1/8 Myotonic and 3/8 Boer.

3. Total is 3/8 Myotonic, 2/8 (or ¼) Pygmy, and 3/8 Boer.  (37.5% Myotonic, 25% Pygmy and 37.5% Boer)

This formula will come in handy any time you wish to calculate percentages of breeds in a crossbred animal.  Remember:  if the outside influence is less than 5%, this is not genetically significant.  In other words, a goat that is 31/32 (greater than 95%) of a specific breed is considered a full blood.