A male donkey can mate with a female horse and give birth to a mule ("horse mule"). If a male horse mates with a female donkey, the child will be called a "donkey mule". The mule is large and has the characteristics of a donkey. It has the ability to bear weight and resistance, and has the flexibility and running ability of a horse. It is a very good draft animal, but it is sterile. Donkeys and mules are small and generally not as good as horses and mules, but they can sometimes give birth.
The genes of male horses and female donkeys combine more easily, so most mules are cross-bred this way. However, the chances of genetic combination are still very small: it took some horses 6 years to successfully mate and get the donkey pregnant. Male and most female mules are born sterile. The inability to reproduce is because the two species have different numbers of chromosomes: donkeys have 62 chromosomes and horses have 64. The female mule has sexual function and the uterus can carry an embryo, but the most difficult part is getting the female donkey pregnant.
Mules that are interspecific hybrids (including mules born from a male horse and a female donkey and mules born from a male donkey and a female horse) are generally sterile. However, at all times and in all over the world, there is no lack of occasional sightings of female mules and females capable of giving birth to foals. Of course, it is also possible to occasionally see the backcross generation, namely B1, produced by them. In ancient Chinese books, the offspring of a male horse and a female mule are called 駏, and the offspring of a male donkey and a female mule are called 鉉. Typical examples of domestic female mules giving birth to foals are reported by Zong Enze and others from the Lanzhou Institute of Animal Husbandry, Chinese Academy of Agricultural Sciences, who conducted many years of systematic research. The total number is about 13. We will not go into detail here. Now we will refer to foreign mules. The relevant case reports of mules giving birth to foals are introduced below for the reference of Chinese people.
The earliest foreign record is a book written by Herodot translated by Russian husband G. Mischenko in 1888 - "Historical Stories in Nine Books", about Babylon around 600 BC. When London was besieged by the Persian Empire, in order to ensure the food supply for the war, there was a transport team composed of mules. On the way, a female mule unexpectedly gave birth to a foal.
In 1992, H. Henseler wrote in the relevant chapter of the German "Annals of Animal Husbandry Science and Technology" that in 1759 there was a case of a female mule born by a female horse in Ettingen. Next came a mule foal, but this one looked very similar to the foal. He also wrote that in Valencia in 1762, there was a case in which a female mule born to an Andalus mare gave birth to 6 offspring (B1) in her lifetime. These offspring were no different in appearance from foals. The author also reported a case in Algier in 1873 of a male horse mated with a female mule and the birth of an offspring. Most notably, the author also reported a case in which a female mule named "Moore" mated with an Arabian stallion at an experimental station in Tripolitania and gave birth to two horses that looked exactly like horses. Later, he mated a male donkey with "Moore" and gave birth to twin colts. However, the appearance of the two foals born this time is typical mule foals.
In the 1916 German "Annals of Animal Husbandry Science and Technology", P. Dechambre reported that a female born from the mating of a white Egyptian male donkey and an Arabian mare was found in Boulogne, France. The mule has given birth to five foals (B1), three of which are sired by Berber stallions (a local breed in North Africa), and two are sired by Egyptian male donkeys. The first three horses were named "Kumil", "Constantine" and "Genpupan". They were the same as horses in appearance, and they were all fertile. The latter two are of typical mule appearance and are sterile. DeChambre also mentioned in the article that as far back as 1898, there were cases of female mules giving birth to foals in India.
In 1928, A.R. Groth reported in the Journal of Heredity that there was a female named "Alder Back" at the Texas Agricultural College in the United States. The mule was mated with a riding stallion in 1923 to give birth to a male foal (B1). The colt was very similar to its father and was no different in appearance from the horse. It is worth noting that this male foal born from a mule had normal sexual function as an adult, and in 1926 he was mated to two mares, one of which became pregnant and gave birth to a female horse with a physical appearance that was very similar to that of the female horse. Foal (B2).
Later, he was bred to several mares and gave birth to a male foal (B2). Their offspring are all capable of reproduction.
The author also wrote that the female mule "Old Byker" had mated with a male donkey in 1919 and gave birth to offspring, but its appearance was that of a typical mule and it was sterile. of. In 1924, another male donkey was used for mating. Although she became pregnant, she later miscarried.
A. Warren (1926) once reported that in 1924 in South Africa, a female mule named "Firth" was mated with a male horse and gave birth to a foal. The foal had the same appearance as a horse. The foal was 7 Later in the year, she mated with a stallion during a heat and became pregnant and gave birth to a foal. Its appearance was no different from that of a horse.
W.S. Anderson reported in the "Journal of Genetics" in 1939 that a female mule mated with a Bell Sherron stallion and gave birth to a foal, which had all the characteristics of its father, the Bell Sherron stallion. Characteristics without any of the characteristics of its maternal grandfather, the donkey.
There are many foreign reports of mules giving birth to foals. For example, Muller reported that a mule gave birth to a foal in Estanz, Africa in 1903; Harveu reported that a female mule mated with a male donkey on Cyprus Island in 1913 and gave birth to a male. The foal then came into heat and was bred with a male donkey (still using a male donkey), and gave birth to another female foal; Montpair once reported that in 1923 in Morocco, a female snail was mated with a riding Berber stallion and gave birth to a foal. Similar to its father - Berber horse; Laurence once reported that in 1927, a female mule in Nebraska, USA gave birth to a foal by a male donkey; H. Smith once reported that in 1939 In Arizona, USA, a female mule was mated with a male donkey and gave birth to a foal, which was exactly like its mother, a mule.
From the above-mentioned examples of mules giving birth to foals, it seems that the following impressions can be given:
(1) As interspecific hybrids, a few individuals of mules (including mules) have the following characteristics: Fertility;
(2) A very small number of fertile adult female mules can give birth to offspring (B1) when mated with male horses or male donkeys;
(3) When used The B1 born when a male donkey is backcrossed not only still has the typical appearance characteristics of a mule, but is also sterile;
(4) The B1 born when a female mule is backcrossed with a male horse not only has the same physical appearance as They are exactly the same as horses, and both males and females are fertile and can give birth to B2, which has completely the appearance and physical characteristics of a horse;
Based on the above points, it seems to prove Anderson's regression theory. However, to confirm the regression theory, karyotype analysis remains to be performed.