Hermaphroditism and Polled Goats
What causes an intersex or freemartin goat?
Reading Time: 5 minutes
Freemartin goats and hermaphroditism are not uncommon, especially in dairy goats of Western European descent. Before people realized the correlation between polled goats, hermaphrodite percentage rates were as high as 6-11% of goat herds in the U.S in the early 20th century. That high percentage did not bode well for those attempting to make a profit either from milk or selling kids. Therefore, even before we truly understood what a chromosome was, studies were being made as to why there were so many hermaphrodite goats in the dairy herds.
Before we get into why goat hermaphroditism (also called intersex) happens, I do need to make a few clarifications. You see, a true hermaphrodite only happens in mammals when an animal has the genes for being both female and male. They have both XX and XY genes found in their DNA. This is typically the result of chimerism, or when two fertilized eggs or very young embryos of opposite sexes fuse together and develop into one baby. That baby, the true hermaphrodite, has gonads of both sexes. The external genitalia may be ambiguous or it may appear very much one sex. There is potential for a true hermaphrodite to be fertile₅. Mosaicism is often confused with chimerism. While chimerism happens when two fraternal twins fuse, mosaicism happens when a single egg has a mutation after having split a few times, and that mutation is passed down to a percentage of the body’s cells but not all. Chimeras and Mosaics are quite rare, but they are considered true hermaphrodites₁. Any horned hermaphrodites are either mosaics or chimeras. What this article is mostly about, though, is what we would call pseudohermaphrodites. However, no one wants to read a word that long through the length of an article, and in everyday life they would simply be called hermaphrodites or intersex anyway. So, with apologies for the slight inaccuracy, I will simply use the term hermaphrodite or intersex for the remainder of this article.
What is a (Pseudo) Hermaphrodite?
A (pseudo) hermaphrodite is usually genetically female but has been masculinized. They display either ovaries or testes but are infertile. Their external genitalia can range from looking completely female to looking completely male with all levels of ambiguity in between. While they can be found in other breeds, they have the highest prevalence in dairy breeds, especially those of Western European descent such as Alpine, Saanen, and Toggenburg₆.
The Relation between Intersex and Polled Goats
The gene for a goat to be hornless, or polled, is actually dominant to the gene for having horns. Therefore, if a goat gets a gene for being polled from one parent, but a gene for horns from the other, the goat will be polled. However, that goat can pass on either gene and if it and its mate both pass on the recessive horned gene, they can have horned kids. While hornless goats would seem ideal, they, unfortunately, come with a downside. Apparently, either directly connected to or very close on the same chromosome is a recessive gene that causes hermaphroditism. It is very interesting that this gene is (fortunately) recessive while the polled gene is dominant. However, if you breed two polled goats together, and they both pass on that polled gene with its tag-along intersex gene, that recessive gene will affect the kid₂. If the kid is male, they will appear unaffected physically. Often, the fertility of that male is affected, but there have been cases of homozygously polled male goats siring many kids. However, if the kid is genetically female, there is a high probability of that female being a hermaphrodite with masculine characteristics and sterile. Yet, the recessive intersex gene also has incomplete penetrance. That means that even when you have a group of kids that all have both recessive genes, not all of them will express the genes₄. This may account for why some of the homozygous bucks are infertile while others are not. Also, not all females born with the recessive intersex genes will be intersex. Yet, you will never find a horned goat with this type of hermaphroditism because they will always have the dominant gene overriding the intersex gene. Dr. Robert Grahn at the University of California at Davis has been studying the genetics of the polled intersex syndrome in hopes of developing a test for it. When asked what needs to happen before he can develop a test he responded, “What I would want to do is some whole-genome sequencing of some intersex goats. However, in the course of additional readings, I came across this 2/2020 article. It appears as though Simon et al may have solved the problem already. I would want to validate their findings across breeds.” It appears that we are getting closer to having a test for the polled intersex gene.
We have neglected one more way in which a goat may be intersex. Freemartin goats are not common. This is a condition seen more often in cattle but can happen in goats. A freemartin goat is genetically female but with much higher levels of testosterone and is sterile. This happens when she has a male twin, and their placentas merge early enough in the pregnancy that they end up sharing some blood and hormones. This higher level of testosterone causes underdevelopment of her reproductive tract. The male twin is unaffected by this exchange. Due to the blood and other cell transfer, the blood of a freemartin goat would have both XX and XY DNA. This makes them a kind of chimera without the fusion of embryonic cells, just the membranes in utero₃. Often, a blood test is needed to distinguish freemartin goats from polled hermaphroditism.
Potential Benefits of Hermaphrodites
Now, hermaphrodite goats aren’t all bad. Some owners have found that they make great companions for bucks. Granted, this works better when they are the pseudohermaphrodite so you know they are guaranteed to be sterile. Because they still have female characteristics, they can be used to tease the bucks to gear up for breeding. In much the same way, they also have the same pheromones as bucks and can excite the does when kept with them, giving you a clear indication of heat cycles. In another way, a true hermaphrodite goat may be very valuable. Tia, a goat owner and practicing Pagan, values the very rare true hermaphrodite that is fertile. While not all Pagan and alternative faiths have this same view, for Tia the milk, especially from the hermaphrodite goat would be very valued for use in ceremonies. This is because the true hermaphrodite embodies both the male and female in one which is a realization of the divine.
There are multiple causes of goat hermaphroditism, but the most common is that of breeding two polled dairy goats to each other. The other causes can’t be avoided, but are fortunately very rare. Yet, if you do end up with an intersex goat, they do not have to immediately be culled, because there is still value for those who want it.
(1)Bongso TA, T. M. (1982). Intersexuality associated with XX/XY mosaicism in a horned goat. Cytogenetics and Cell Genetics, 315-319.
(2)D.Vaiman, E. L. (1997). Genetic mapping of the polled/intersex locus (PIS) in goats. Theriogenology, 103-109.
(3)M, P. A. (2005). The freemartin syndrome: an update. Animal Reproduction Science, 93-109.
(4)Pailhoux, E., Cribiu, E. P., Chaffaux, S., Darre, R., Fellous, M., & Cotinot, C. (1994). Molecular Analysis of 60,XX pseudohermaphrodite polled goats for the presence of SRY and ZRY genes. Journal of Reproduction and Fertility, 491-496.
(5)Schultz BA1, R. S. (2009). Pregnancy in true hermaphrodites and all male offspring to date. Obstetrics and Gynecology, 113.
(6)Wendy J.UnderwoodDVM, M. D. (2015). Chapter 15 – Biology and Diseases of Ruminants (Sheep, Goats, and Cattle). In A. C. Medicine, Laboratory Animal Medicine (Third Edition) (p. 679). Academic Press.
Originally published in the September/October 2020 issue of Goat Journal and regularly vetted for accuracy.