Grey horses with dense speckling are more likely to be heterozygous for grey.
In the previous two posts, we looked at how the placement of the fleabites could vary. Another way that fleabitten greys differ from one another is in the density of their speckling pattern. If you have visited the Kentucky Horse Park during BreyerFest in the last few years, you may have seen the pony pictured at the top of this post. The intensity of his pattern set against his white mane and tail is certainly eye-catching.
Fleabitten greys with this type of speckling pattern do not always show as much change in density from their topline to their undersides.
Typically, there is still a difference in spot density on the belly, but it is more subtle. There is also heavy speckling on the insides of the upper legs, which is another area that often has fewer fleabites.
The famed Polish Arabian mare Bandola (f. 1948) was a great example of this type of greying. Another is the Arabian stallion Papillon.
Images of him, including the two included above, have been widely shared online. Two more can be seen here and here. Dense fleabites like this seem more common in Arabians than in other breeds, but it is not exclusive to them. The Wielkopolski (Polish Warmblood) mare Orkiestra and this grade Quarter Horse are examples of non-Arabians with this type of fleabitten pattern.
Geneticists who have studied greying have looked at fleabiting, which in scientific literature is usually referred to as “speckling.” One study done in 2013 specifically addressed the density of the spotting pattern. As with many of the studies on greying, Lipizzaners were used. Horses were assigned grades from 0-3 based on the number of speckles per square decimeter. Horses with patterns like the pony in this post would be a Grade 3.
Results from the study supported the idea that the density of the pattern has a genetic basis. That makes sense since it is more common in some breeds and even within certain families. Another finding that was not surprising was that more heavily speckled greys were more likely to be heterozygous for grey. It has long been believed that homozygous greys did not develop fleabites, or at least not many. What was surprising was that when researchers used a large sample set (1,119 horses), some of the horses with higher levels of speckling were homozygous for grey. Horses with higher grades of speckling were much more likely to be heterozygous, but it wasn’t absolute. Another interesting finding was that there was a negative correlation between a higher grade of speckling and developing melanomas.
As I mentioned at the top of this post, I find the contrasting white mane and tail to be one of the most attractive features of this type of fleabitten grey. Color – of both the long hair and the spots themselves – is a question that comes up frequently when talking about fleabiting. I am often asked, “Are the mane and tail always white?” and “Are the spots always red?” The answers to those questions will be the subject of the next post.