Homozygous Appaloosa Coat PatternsBy Gene Carr and Robert A. Lapp
“Few spot and snowcap coat patterns. Stallions studied each produced anywhere from 35 to 160 registered foals, involving from at least 11 to 84 QH/JC/CN/PC/ID mares per stallion.”
This report explores only a portion of the complex topic of Appaloosa color genetics and coat pattern inheritance. Our approach is practical rather than theoretical. We call it applied color genetics, the study of the relationship between an Appaloosa stallion's or mare's coat pattern (phenotype) and color production, or the extent to which a given coat pattern structure or type predicts the likelihood of an expressed coat pattern (color) in any resulting foals.
What, if any, is the correlation between the type of coat pattern an Appaloosa expresses and the probability of producing color or characteristics in any offspring? Stated differently, is an Appaloosa's visible coat pattern indicative of its genetic color-producing potential or genotype?
While many of the genetic rules governing inheritance of Appaloosa color may remain hidden forever or continue to be the subject of mere speculation by color geneticists, we believe we have found substantial real-world evidence for several of these rules. Our report is not speculative, but based on data that seems to be overwhelming.
This article continues a research effort started years ago by Gene Carr and published in the Appaloosa News' November/December 1972 issue entitled, "Few-Spotted Leopards". His purpose then, as is ours now, was described in the article's opening paragraph: "Economics has prompted Appaloosa breeders to investigate systems of increasing the percentage of color in their foal crops."
While we hope to advance the scientific understanding of Appaloosa color genetics and coat pattern inheritance, our basic intent is more practical -- helping Appaloosa breeders understand how to produce a foal with color, or at a minimum, characteristics. Furthermore, we hope to impact on the market value of Appaloosas. If someone owns a "good" Appaloosa, and that stallion or mare can be predicted to produce an astonishingly high rate of colored foals, we believe the value of such an Appaloosa will increase dramatically.
Few spots and Snowcaps
To date, this research has identified two homozygous Appaloosa coat patterns, the few spot and the snowcap. (See accompanying photos: Group A represents the classic few spot; group B classic snowcaps. "Classic" means the most recognizable pattern, allowing for some variations that'll be covered in further research reports.)
These patterns are homozygous, meaning such a horse carries identical genes for either of two traits: color--contrasting coat pattern, or characteristics, and often both. When a pair of genes is different, one dominant and the other recessive, the horse is heterozygous for that particular trait (color). Sometimes they will produce colored offspring, sometimes they will not. When a pair of genes is identical, that trait will be produced nearly 100 percent of the time. But how can this be determined at an applied versus theoretical level?
Carr was the first person to identify a few spot pattern and in fact, coined the term "few spot leopard". The "leopard" derives from lineage or parentage. The few spot is produced only from an Appaloosa to Appaloosa breeding where as at least one parent is a leopard. Such findings were based on observations of his own horses and the findings of several other breeders. Later research brought the snowcaps into the probable homozygous category but lacked the abundance of supporting data we are now able to present.
Without the development of genetic markers for homozygosity and actual DNA testing, how do we know these patterns are homozygous? A short explanation of the research methodology I used will explain the basis for our claim. (Note: to our knowledge, no Appaloosa stallion or mare has ever been tested scientifically to support a claim of homozygosity.)
This research has studied the individual pictures and production records of nearly 2,000 Appaloosas and Quarter Horse stallions and mares. From that sample, well over 200 Appaloosas, past and present, were identified as few spots or snowcaps, documented by their actual production records. Many more probably exist but could not be confirmed because of poor quality pictures.
Analysis of pictures, pedigrees, and production records warrants the following observations:
We suspect that certain types of coat patterns will not produce either a few spot or snowcap but are conducting further studies. Likewise, we suspect that certain coat patterns necessarily evidence heterozygosity, regardless of pedigree or parentage. Understand clearly, however, that two heterozygous Appaloosa parents can and have produced homozygous horses which, at this point, we have identified as few spots and snowcaps.
While this report focuses only on few spots and snowcaps we believe some other Appaloosa coat patterns or structures may well be homozygous but lack a sufficient data base for justifying any conclusions. Research is on-going.
We are not attempting to return to the days during which too many breeders ignored quality and bred primarily for color. Nor are we content with some current efforts n which color has become very much a secondary consideration to quality. We believe breeders ought to and can have it both ways. We hope our research will increase the likelihood of achieving it.
These stallions each produced anywhere from 35 to 160 registered foals, involving from 11 to 84 QH/JC/CN/PC/ID mares per stallion. The snowcap stallions produced 100 percent color/characteristics at the time of registration. Several of the few spots produced no more than one or two N/C registered foals, but from a total foal production of 102 and 91 foals respectively.