There are a few traits in goats that we know follow a simple type of inheritance - the trait is controlled by just a single pair of genes and those genes are either dominant or recessive. Using the Mendelian Punnett square, breeders can determine the probability of inheritance for these traits. We can calculate the possibilities of blue or non-blue eyes (golds &browns etc.), wattles or non-wattled, and polled or horned. In LaManchas and LaMancha crosses, we can also determine if the ears will be gopher, elf, or erect (anything larger than an elf ear).
I won't go into great detail about the terms associated with Punnett squares, but do give it a Google if you're curious for more detail!
The method is fairly simple once you know what traits are dominant or recessive. Here's what we know about goats:
Blue eyes are dominant.
Wattles are dominant.
Gopher ears are dominant.*
Polled is dominant.
Genetically dominant traits will be expressed phenotypically (physically - you will see it!) if there is either one or two copies of that dominant gene. There must be two recessive genes to express phenotypically.
Let's start with polled or horned. A horned goat has two copies of the horned gene, always. It will never carry a copy of the polled gene. However, a polled goat can either be heterozygous polled (1copy of the dominant polled gene and one copy of the recessive horned gene) or homozygous polled (2 copies of dominant polled gene).
Now, you cannot tell if animal is heterozygous or homozygous polled (or blue-eyed or wattled) just by looking at it. It may take a few breedings to different animals to determine the genetic status. If your polled animal has EVER sired or birthed a horned kid, then you know that animal CANNOT be homozygous polled because remember that a recessive trait must have two copies to express; it must be heterozygous polled if it has ever birthed or sired a horned kid.
Let's make some Punnett squares! The method is fairly simple. Write the gene pair for each parent, one across the top and one vertically on the side. Drop the corresponding letter into each quadrant. Here's one for parents with heterozygous traits. Each quadrant is a 25% chance of that trait being expressed. So in this example, there's a 25% chance of a homozygous AA, a 50% chance of a heterozygous trait (Ab) and a 25% chance of the recessive trait being expressed (bb).
Trust me - it can sound more complicated than it actually is!
Let's do a couple for polled and horned. Assign each parent the appropriate genes. Typically, as illustrated above, you choose a capitalized letter for the dominant trait and a lower case letter for the recessive trait. A homozygous dominant trait is written as two capital letters - in our polled example this would be PP. Heterozygous will have a capital letter and a lower case letter. The homozygous recessive trait will be two lower case letters.
For our purposes, the letter really doesn't matter as long as you are consistent with whatever you choose and the method is correct. For this, because it was hard to distinguish between P and p, I used the capital P for polled and the lower case h for horned. In the examples below, I calculated the possibilities for the offspring of a homozygous polled parent and heterozygous polled parent and then the possibilities for the offspring of two heterozygous polled parents.**
If you want to do another possible combination on your own, try the one for a heterozygous polled goat bred to a horned goat. (A combo that happens here a lot!)
Obviously, two horned goats will always produce 100% horned offspring and two homozygous polled goats will always produce 100% homozygous polled offspring, so I did not make charts for those.
**there are some considerations when breeding polled goats, especially two polled goats but that is another post.
Let's go on to eye color. What I think is interesting is that two blue eyed goats CAN give you a brown-eyed offspring but two brown-eyed goats will never result in blue-eyed offspring. Blue eyes, contrary to some old articles on the internet, do not skip a generation or two and crop up out of nowhere. If there is ever a question of parentage or if your two brown eyed goats have blue-eyed offspring - well sorry but they didn't. DNA testing is your friend! Now, some newborns have do have very light colored eyes. If you don't have a blue-eyed goat to compare to, you might think that light baby gray is blue. If it is a genetic possibility, wait and see! If it isn't, (i.e. both parents have brown eyes) then you can now confidently say to yourself, "Ah, these are not blue eyes."
Check out the first Punnett square for eye color down below and see what happens when you cross two heterozygous blue-eyed goats. For a bit, I thought Storm might be homozygous blue-eyed. Her kids, when bred to a brown-eyed buck, had been blue-eyed. Then I bred her to a blue-eyed buck, Duke, and got 2/3 brown-eyed kids! So that alone told me both Storm and Duke were heterozygous blue-eyed. While there was only a 25% chance that would occur, it did in the same litter, twice. (And no - there was no mistake on any of these breedings I am talking about because of my pasture set up - acres in between bucks and does -and breeding methods - hand breeding. I do DNA test if anything is in question. Also, two of the kids were gopher eared so I know they couldn't have been sired by a Kinder buck.)
On the flip side, take a look at the graphic on the right. Rhea has brown eyes and had ALL blue-eyed kids (six in total out of three litters) when bred to bucks I KNEW were heterozygous blue-eyed. There was only one blue-eye gene in the mix, but it cropped up every time. She actually did not have a brown-eyed kid until she was bred to a brown-eyed buck, and then of course there was no other possibility. So, even though the probability of inheriting a trait might be 50% (or 25%), it is possible you hit the weird probability lottery and it happens 100% of the time. (I am sure someone math-brainier than I am could explain that better and give you some fancy terms for it. I cannot.) To my knowledge, I do not have a homozygous blue-eyed goat. The only one that MIGHT be is Zenyatta, out of Storm and Churro. I know they are both heterozygous blue-eyed so there's a 25% chance Zenyatta is homozygous blue-eyed; I won't know until she kids and has a brown-eyed kid or not.
I did not make any graphics for wattles, but they follow the same principle as polled/horned or blue-eyed/not blue-eyed. Good chance for you to practice and make your own! I think it is interesting to point out that goats can have only one wattle. So they still carry the dominant wattle gene but for whatever reason, it resulted in one wattle instead of two.
Lastly, let's look at ears! I think this is fun because each ear gene possibility is expressed by a different phenotype. Erect ears (or pendulous or airplane - anything other than a LaMancha type ear) is recessive. *We know gopher ears are dominant - these are the LaMancha ears with an inch or less of cartilage, but they are an incomplete dominant. Here is the definition from Biology Online: "The incomplete dominance is referred to as the dilution of the dominant allele with respect to the recessive allele, resulting in a new heterozygous phenotype." So, when you get a heterozygous pair of ear genes, it expresses phenotypically as an elf ear! The cute little "long" LaMancha ear type, where the cartilage is over an inch long. Some examples in my herd are Toot, Nebula, Ursa, and Storm. (I am biased - I love elf ears.)
In standard LaManchas, of course, you see only gopher or elf ears. In miniature LaManchas, you can see any ear type though only gopher are acceptable after a certain number of generations in the two registries. Some of the ears hovering between elf and gopher can be a tricky, especially for new breeders, so it might take some breeding to figure out which is which or you can always ask more experience breeders for some insight. In my herd, most have been easy to tell apart. Creamcup herd has a great page about those hard in-between ears here.
Check out the graphic below, breeding an elf ear to an erect ear. What I think is fun is you even see some lovely high percentage Boer does with elf ears - it can easily persist for generations because any time you breed an elf ear to an erect ear, you still have a 50% chance of an elf ear. On the flip side, those elf ears from one erect ear in a line otherwise filled with gopher ears is possible, too. Nebula is a fun example. She is very high percentage LaMancha and only 1/32 Alpine but she has elf ears still from that one half Alpine several generations back. Her dam and granddam and great granddam and great great granddam were all elf-eared. As shown below, breeding two elf-eared animals could result in offspring of any ear type!
Maybe I knew this information once upon a time in AP biology or something, but you can also do a dihybrid cross Punnett Square, where you calculate the possibilities of two traits at once. This is a fun video explaining that if you'd like to give it a try! https://www.youtube.com/watch?app=desktop&v=qIGXTJLrLf8 Or if you'd like to figure two traits but that's way too many letters to keep track of - here's a calculator to do it for you - you just have to assign an A or B to each trait in your head. https://www.omnicalculator.com/biology/dihybrid-cross-punnett-square Heck, you want to get really crazy, that same website has a trihybrid calculator. Or you can just wait and see what you get, which is my preferred method (ha!).
Now, here are a couple anomalies that I've yet to find an definitive answer to. Goats can have marbled eyes. Meaning the irises are blue and another color like gold or brown. I have had a marbled eye goat but she only kidded here once. Both kids had blue eyes showing marbling like their mother sired by a brown eyed buck. Obviously the blue gene is still dominant, but maybe the marbling is too?
Tiny erect ears - some folks call them Shrek ears. Some non-LaMancha goats - the ones I've seen have all been Swiss breeds - might crop out with a tiny erect ear. My guess is they are still genetically an erect ear and just a weird anomaly. (I've seen some photos of these but have been unable to relocate them - if anyone has one they're willing to share, please send it my way!)
Here's just a few pictures of some goaties over the years. I honestly still have trouble telling some polled kids from horned kids! Especially in the case of multiples (usually smaller and born a little earlier) where the buds may take several days or even over a week to be felt. Some folks have good luck telling them apart with hair swirls (horn buds have swirls over them) and head shapes (polled are usually rounded). There are some good examples of these methods online. I usually just wait until I can feel a bud or not. The best way I know to describe it is a horn bud will feel like a small coin under the skin. Polled feels like nothing at all or just a rounded head or more gradual bump. The skin on polled kids usually moves more freely than horned kids. There are couple different "styles" of polled, including one dubbed giraffe polled where the goat in question has noticeable tall bumps in place of horns. Another term you might hear is "scur polled" where the animal is genetically polled but still gets small abnormal horn growth; it is usually wiggly and breaks off easily. Some folks use these terms interchangeably, and there is no "official" definition, to my knowledge. Happy goating!
