Sheep-goat hybrid

A sheep–goat hybrid is the hybrid offspring of a sheep and a goat. Although sheep and goats seem similar and can be mated together, they belong to different genera. Goats belong to the genus Capra and have 60 chromosomes, while sheep belong to the genus Ovis and have 54 chromosomes. This mismatch of chromosomes means any offspring of a sheep-goat pairing is generally stillborn. Despite widespread shared pasturing of goats and sheep, hybrids are poorly attested, indicating the genetic distance between the two species.

History

At the Botswana Ministry of Agriculture, a ram that was kept with a nanny goat impregnated the goat resulting in a live offspring that had 57 chromosomes. This was called "The Toast of Botswana". The hybrid was intermediate between the two parent species in type. It had a coarse outer coat, a woolly inner coat, long goat-like legs and a heavy sheep-like body. Although infertile, the Toast of Botswana had to be castrated to prevent unwanted sexual behaviour because it continually mounted the sheep and goats sharing its enclosure. [http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=10818315&dopt=Abstract Sheep-goat hybrid born under natural conditions. [Small Rumin Res. 2000] - PubMed Result]

In 1969, Australian farmer Dick Lanyon, who farmed near Melbourne, Australia, kept a billy goat among his sheep to scare off foxes during the lambing season. In September of the same year, he claimed to have dozens of ‘lambs’ which were sheep-goat hybrids. The goat was locked up while scientists examined the supposed hybrids. As no more was heard of this case, it is believed that the lambs were pure-bred sheep.

Characteristics

There is a long-standing belief in sheep–goat hybrids, which is presumably due to the animals' resemblance to each other. Some primitive varieties of sheep may be misidentified as goats. In "Darwinism – An Exposition Of The Theory Of Natural Selection With Some Of Its Applications" (1889), Alfred Russel Wallace wrote:

[...] the following statement of Mr. Low: "It has been long known to shepherds, though questioned by naturalists, that the progeny of the cross between the sheep and goat is fertile. Breeds of this mixed race are numerous in the north of Europe." Nothing appears to be known of such hybrids either in Scandinavia or in Italy; but Professor Giglioli of Florence has kindly given me some useful references to works in which they are described. The following extract from his letter is very interesting: "I need not tell you that there being such hybrids is now generally accepted as a fact. Buffon ("Supplements", tom. iii. p. 7, 1756) obtained one such hybrid in 1751 and eight in 1752. Sanson ("La Culture", vol. vi. p. 372, 1865) mentions a case observed in the Vosges, France. Geoff. St. Hilaire ("Hist. Nat. Gén. des reg. org.", vol. iii. p. 163) was the first to mention, I believe, that in different parts of South America the ram is more usually crossed with the she-goat than the sheep with the he-goat. The well-known 'pellones' of Chile are produced by the second and third generation of such hybrids (Gay, 'Hist, de Chile,' vol. i. p. 466, "Agriculture", 1862). Hybrids bred from goat and sheep are called 'chabin' in French, and 'cabruno' in Spanish. In Chile such hybrids are called 'carneros lanudos'; their breeding "inter se" appears to be not always successful, and often the original cross has to be recommenced to obtain the proportion of three-eighths of he-goat and five-eighths of sheep, or of three-eighths of ram and five-eighths of she-goat; such being the reputed best hybrids."

Supposedly, most sheep–goat hybrids die as embryos (the famous geep is a chimera, not a hybrid). Hybrid male mammals are often sterile due to a phenomenon called Haldane's rule. The Haldane phenomenon may apply even when the parent species have the same number of chromosomes, as in most cat-species hybrids. It sometimes does not apply when the species chromosome number is different, as in wild horse (chromosome number = 66) with domestic horse (chromosome number = 64) hybrids. Hybrid female fertility tends to decrease with increasing divergence in chromosome similarity between parent species. Presumably, this is due to mismatch problems during meiosis and the resulting production of eggs with unbalanced genetic complements.

See also

* Sheep-goat chimera

References