# Hinny
A **hinny** is the sterile hybrid offspring of a male horse (stallion) and a female donkey (jenny or jennet). It is the reciprocal cross of the mule, which comes from a male donkey (jack) and a female horse (mare); both hybrids carry 63 chromosomes and are among the most common equine hybrids, though hinnies are far less frequently produced than mules.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC9951644/)
| Key fact | Detail |
|---|---|
| Parentage | Male horse (stallion) × female donkey (jenny); the mule is the reverse cross[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/) |
| Chromosomes | Horse 2n = 64, donkey 2n = 62, hinny and mule 2n = 63[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/) |
| Fertility | Nearly all hinnies are sterile; the block occurs at meiosis during gametogenesis[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC4852245/) |
| Rarity | Inseminating jennies with stallion semen gave a 16.3% pregnancy rate (8/49), the lowest of the four horse-donkey combinations, versus 42.9% (6/14) for mules[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC9951644/) |
| Appearance | Generally smaller than a mule, with a more horse-like head, shorter ears, and a lighter build; body proportions and tasselled tail resemble the donkey mother[4](https://scienceinsights.org/what-is-a-hinny-horse-and-how-it-differs-from-a-mule/) |
| Resting temperature | 37.06 °C ± 0.46 °C, closest to the donkey; horse and mule measured 37.24 °C ± 0.55 °C (p = 0.005)[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/) |
| Historical record | Distinguished from the mule by Roman writers of the first century, Varro and Columella, as the "burdo" or "hinnulus"[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/) |
## Definition and naming
The hinny results only from the pairing of a stallion with a jenny; swapping the sexes of the parents produces a mule instead. The two hybrids share the same parent species but differ in size, appearance, temperament, and physiology, because the mother's species shapes gestation and early development.[4](https://scienceinsights.org/what-is-a-hinny-horse-and-how-it-differs-from-a-mule/) The English word is first recorded in 1680–90, from the obsolete *hinne*, taken from Latin *hinnus* (akin to Greek *gínnos*, "mule") plus the suffix *-y*.[5](https://www.dictionary.com/browse/hinny) An older 19th-century account adds that *hinnus* derives from the Latin verb *hinnire*, "to neigh", and observes that the hinny neighs while the mule brays.[6](https://en.wikisource.org/wiki/Page%3AHints_to_Horse-keepers.djvu/90)
The distinction is old. First-century Roman agricultural writers, including Marcus Terentius Varro and [Columella](https://www.edgepedia.org/columella), described the *mulus*, offspring of a mare and a jack, separately from the *burdo* or *hinnulus*, offspring of a male horse and a jenny.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/)
## Genetics and sterility
Horses and donkeys can interbreed despite different chromosome numbers: the horse contributes 32 chromosomes to the hybrid and the donkey 31, and structural chromosome differences that accumulated over evolutionary time cause irregularities when homologous chromosomes pair at meiosis.[7](https://www.cambridge.org/core/services/aop-cambridge-core/content/view/DC926E59BD32C77E6576D00A9F757A5A/S001667230002005Xa.pdf/does-affinity-hold-the-key-to-fertility-in-the-female-mule.pdf) This meiotic failure makes nearly all hinnies and mules sterile.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC4852245/)
**Male sterility is well characterized.** A histological study comparing a mature male hinny with a fertile stallion and a jack donkey found that hinny testes had a thicker tunica albuginea, fewer blood vessels, and more connective tissue in the parenchyma. The proportion of seminiferous tubules was lower, giving them a smaller diameter, and the numbers of spermatogonia and spermatocytes per unit area were significantly reduced. No spermatids or mature spermatozoa were found; most germ cells cease development during synapsis in mid-meiosis, blocking spermatogenesis entirely.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC4852245/)
Fertility in female hybrids is rarer still. There have been documented cases of fertility in the female mule, but not in the female hinny.[8](https://www.ontario.ca/page/management-recommendations-donkeys-and-mules) Because the chromosomes a hinny or mule gets from its two parents differ in structure, these hybrids almost never succeed in producing offspring with one another.[9](https://www.countryfile.com/animals/horses/hinny-vs-mule)
## Why hinnies are rarer than mules
Producing a hinny is biologically harder than producing a mule. In a controlled artificial insemination study at Pisa University using the same stallions and jennies across all cross combinations, pregnancy rates differed sharply by genotype: horse × horse 87.5% (14/16), donkey × donkey 52.4% (11/21), donkey stallion × mare (mule) 42.9% (6/14), and horse stallion × jenny (hinny) 16.3% (8/49). Overall interspecific insemination gave 22.2% pregnancies against 67.6% for intraspecific crosses (p = 0.0001), and the hinny combination was the least successful.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC9951644/) The only previously published study of stallion × jenny insemination had reported a similarly low 14% pregnancy rate.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC9951644/) The mechanisms behind this disparity between reciprocal crosses remain unknown; comparable asymmetries occur in other species, such as goat × sheep and rabbit × hare crosses.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC9951644/)
## Appearance and physiology
Hybrid equids tend to inherit general body proportions from the mother and head and front-end features from the father. Because hybrids generally take body proportions from the mother and head and forequarters from the father, a hinny's head, shorter ears, and lighter frame recall the horse sire, while its build and tail follow the donkey dam; the result often looks like a compact little horse, in contrast to the plainly donkey-like mule.[4](https://scienceinsights.org/what-is-a-hinny-horse-and-how-it-differs-from-a-mule/) Older breeding manuals describe the hinny as essentially a modified horse, smaller than its sire and approaching its dam in size and in the narrowness of its trunk.[10](https://definition.org/define/hinny/) Without documented parentage, even experienced equine professionals can struggle to tell a hinny from a mule by appearance alone.[4](https://scienceinsights.org/what-is-a-hinny-horse-and-how-it-differs-from-a-mule/)
Physiology also follows the mother's species. A study of healthy mules and known hinnies established reference values for blood chemistry and hematology and found a significant difference in resting temperature between the two hybrids: the hinny averaged 37.06 °C ± 0.46 °C, closest to the donkey, while the horse and mule were most similar at 37.24 °C ± 0.55 °C (p = 0.005).[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/) A gut microbiome study similarly found that hybrid equids show a pronounced maternal resemblance in their microbiota.[11](https://arxiv.org/abs/2407.05076)
## Temperament and care
Hinnies are generally described as calm and donkey-like in temperament, with added strength from their horse genetics, and as less independent and less challenging to handle than mules.[12](https://resources.pangovet.com/pet-lifestyle/general/hinny-vs-mule/) Like donkeys and mules, they have anatomical and physiological differences from horses that require special consideration in veterinary care; clinical pathology results for donkeys, mules, and hinnies can be difficult to interpret, and transferring reference data from the horse is not always applicable.[13](https://pubmed.ncbi.nlm.nih.gov/31672198/)
## References
1. [McLean AK and colleagues (2019). Comparing and Contrasting Knowledge on Mules and Hinnies as a Tool to Comprehend Their Behavior and Improve Their Welfare. Animals (PMC).](https://pmc.ncbi.nlm.nih.gov/articles/PMC6719969/)
2. [Fanelli D and colleagues (2023). Interspecific and Intraspecific Artificial Insemination in Domestic Equids. Animals 13(4):582.](https://pmc.ncbi.nlm.nih.gov/articles/PMC9951644/)
3. [Testicular Characteristics and the Block to Spermatogenesis in Mature Hinny (PMC).](https://pmc.ncbi.nlm.nih.gov/articles/PMC4852245/)
4. [What Is a Hinny Horse and How It Differs From a Mule, ScienceInsights.](https://scienceinsights.org/what-is-a-hinny-horse-and-how-it-differs-from-a-mule/)
5. [Hinny Definition & Meaning, Dictionary.com.](https://www.dictionary.com/browse/hinny)
6. [Hints to Horse-keepers, "How to Breed Mules", Wikisource.](https://en.wikisource.org/wiki/Page%3AHints_to_Horse-keepers.djvu/90)
7. [Does 'affinity' hold the key to fertility in the female mule? Heredity (Cambridge Core).](https://www.cambridge.org/core/services/aop-cambridge-core/content/view/DC926E59BD32C77E6576D00A9F757A5A/S001667230002005Xa.pdf/does-affinity-hold-the-key-to-fertility-in-the-female-mule.pdf)
8. [Management recommendations for donkeys and mules, Ontario Ministry of Agriculture.](https://www.ontario.ca/page/management-recommendations-donkeys-and-mules)
9. [Hinny vs mule: what is a mule and how does it differ to a hinny? Countryfile.com.](https://www.countryfile.com/animals/horses/hinny-vs-mule)
10. [Definition of hinny, Definition.org.](https://definition.org/define/hinny/)
11. [Metagenomic analysis reveals shared and distinguishing features in horse and donkey gut microbiome and maternal resemblance of the microbiota in hybrid equids, arXiv.](https://arxiv.org/abs/2407.05076)
12. [Hinny vs Mule: Key Differences, PangoVet.](https://resources.pangovet.com/pet-lifestyle/general/hinny-vs-mule/)
13. [Clinical Pathology of Donkeys and Mules, PubMed.](https://pubmed.ncbi.nlm.nih.gov/31672198/)
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*Topic: Encyclopedia › Life and health › Animals › Vertebrates › Mammals › Ungulates › Horses and equids*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license