Stillborns Caused by Inbreeding in Horses

Homozygous Gene Pairs

• Homozygous genes consist of two alleles, one from each parent. These form a gene which is responsible for a given trait in the offspring. Inbreeding or mating two related horses increases the likelihood that identical alleles will form a gene. If the alleles are weaker or inferior, the resulting trait may compromise the health of the fetus.

Nonselective Inbreeding

• Crossbreeding refers to mating horses of different breeds. The less related they are, the less likelihood a given gene in their offspring will consist of identical alleles. Crossbreeding is occasionally used to to reinvigorate a breed or introduce a change.

Considerations

• Intensive inbreeding increases the rate at which undesirable traits occur. Careful study of pedigrees before mating horses prevents that likelihood, according to Craig Stevens, director of the National School of Academic Equitation.