Heterozygotes for ACAN dwarfism alleles in horses have reduced stature.

This research indicates that Miniature horses carrying alleles that cause dwarfism are, on average, shorter than those without the alleles, suggesting that these genetic variants may also influence height in the normal range.

Research Objective

The main aim of this research was to determine if miniature horses carrying alleles (a variant form of a gene) associated with dwarfism have a smaller stature (height) compared to those that do not carry these alleles. The four alleles under investigation are the ACAN D1, D2, D3*, and D4.

Research Methodology

• The study was carried out on a sample population of 245 Miniature horses.
• Each horse was tested for the presence of the four ACAN alleles associated with dwarfism.
• The height of each horse, measured at the withers (the ridge between the shoulder blades), was also recorded.
• Of the 245 horses, 98 were identified as carriers of the dwarfism-causing alleles, and 147 were non-carriers.

Findings

• The study found a statistically significant difference in withers height between the carrier and non-carrier groups.
• On average, horses carrying the dwarfism-causing alleles were 1.43 inches shorter than the non-carriers.
• While a difference was observed, it was noted that the range of heights between the two groups overlapped. This suggests that other factors, including different genes, also play a role in determining the height of the horses.

Conclusion

The researchers concluded that the high carrier rate of these dwarfism-causing variants in the miniature horse population may be related to selective breeding for decreased height. While the ACAN alleles investigated in this study are known to cause dwarfism in their homozygous or compound heterozygous form, their presence in the heterozygous form may also contribute to a shortened stature within the normal height range.