Chromosome studies and other investigations on equid crossings

Crossings between horses and donkeys are in nature possible and are used as mules or hinnies in agriculture. Other types of crossings are rare and scarcely investigated. Systematic experiments are only allowed with special agreements and are very time consuming and costly and therefore rare. In this report crossings between horse, Przewalski and donkey are cytogenetically and histologically investigated and their behaviour in special reproductive traits described. All animals have shown a normal chromosome set following the segregation of possible combinations. The cytogenetic results have been confirmed by a genomescan for the sex chromosomes and the EPR 23 and 24. The consequences in the evolutionary development are discussed.