My color genetics is a little rusty, but I think your best shot of not getting a gray foal is to find a homozygous bay stallion. There will still be a chance you can get a gray. There have been a few TB stallions in the past that have been that way, Seattle Slew and Danzig being most prominent. Theres a TB stallion in FL that I used last year and finally got a bay from my chestnut mare. She’s always had chestnut foals, so that was interesting. I checked a listing of his foals and didnt see any chestnuts. So that might be something to try, if you can find a stallion that you like who is like that.
The best shot of not getting a gray foal is to not breed a gray 
But if you’re starting with 1 gray parent, then assuming that parent is Gg there is no color that lessens the 50/50 shot of gray.
Assuming “homozygous bay” means the horse is EEAA, all that means is the horse would start out as bay, but if bred to a Gg, still has a 50/50 shot of coming out also gray.
Your chestnut mare had a 100 or 50% chance of producing a chestnut foal when bred to anything ee or Ee respectively - chestnut or bay/black/brown (leaving out all other modifications for simplicity), and a 0% chance when bred to EE.
She had no choice but to pass her red. The stallion had the one and only say in whether the foal was chestnut or not.
The fact that he has no chestnut foals nearly guaranteed means he’s EE - homozygous for black, and not capable of producing anything chestnut/palomino/etc.
All that is totally irrelevant when it comes to gray
[QUOTE=epowers;7817752]
Actually, it is that simple. A heterozygous grey has a 50-50 chance of passing grey with each breeding. It won’t produce exactly 50% grey offspring. And it matters if you are breeding a hetero grey to another grey, because then, yes, you will have more than a 50% chance to get grey. When you flip a coin 10 times, you might get heads nine times, and it doesn’t mean the game is rigged, it’s just luck in a very small sample size.[/QUOTE]
Possibly but there are other factors involved in that process that may not let a grey be passed on in the predicted frequency, or even possibly a oddity that affects the expression of it. http://genetics.thetech.org/how-blue-eyed-parents-can-have-brown-eyed-children
And the same may be true for the sex equation. It may be the small sample size that skews the expected results or it may be other factors.
There was a study done with sex of the offspring and the mares condition, and it showed statistically significant results. This is not surprising as there are lots of survival strategies that have evolved to modify a population based on the environment.
So with this type of thinking, then it is possible that a heterozygous grey mare may have something about her recombination process that favours one gene over another.
Having said that, for the OP who is looking to stack the deck, there was nothing you could have breed her to that would have override the grey. If she does have some weird anomaly in what she can throw, there is nothing you can do about that or even know ahead of time.
You should come back when the foal is born to tell us what color it ended up being!
No, there is luck. Good luck and bad luck depending on what you want. We have a heterozygous grey stallion. This year we have a 50% sex split though all the fillies were early and the colts mostly late so we were getting nervous of having a filly year. Last year the majority were colts. We also have a 50% chance of greys. Last year of about 10 foals the last 2 were grey, this year we have 2 as well out of 8. There is still a chance that the last 2 could be grey as they are late foals with winter type coats and may not shed anytime soon…they look non-grey so far. Our 2nd grey is a silver dappled filly and we were sure she was not grey…then her behind shed out…grey…then we got the spectacles around her eyes. Now SHE had a 50% chance of being silver dappled but from two foals, both silver dappled, we can’t yet say if her dam has a chestnut gene. The stallion does have a chestnut gene and a bay gene…may have a black. The silver dappled fillies SEEM to be classic silver dapples so that would be on a black base…the dam is out of a black IDSH stallion and out of a silver dappled medicine hat Paint mare. We also have one filly who may be black. Oh we also have pangere and a grulla dun gene in the mare herd. So as to the luck that gave us 2 grey when we should have had more…then the bad luck of having a special silver dapple…go grey…I expect we will some year have a majority of grey foals. The great pain will be when the grulla dun(with a chestnut gene) mare has a grulla foal…and it goes grey. Color giveth and color taketh away. PatO
[QUOTE=stoicfish;7817995]
Possibly but there are other factors involved in that process that may not let a grey be passed on in the predicted frequency, or even possibly a oddity that affects the expression of it. http://genetics.thetech.org/how-blue-eyed-parents-can-have-brown-eyed-children
And the same may be true for the sex equation. It may be the small sample size that skews the expected results or it may be other factors.
There was a study done with sex of the offspring and the mares condition, and it showed statistically significant results. This is not surprising as there are lots of survival strategies that have evolved to modify a population based on the environment.
So with this type of thinking, then it is possible that a heterozygous grey mare may have something about her recombination process that favours one gene over another.
Having said that, for the OP who is looking to stack the deck, there was nothing you could have breed her to that would have override the grey. If she does have some weird anomaly in what she can throw, there is nothing you can do about that or even know ahead of time.
You should come back when the foal is born to tell us what color it ended up being! :)[/QUOTE]
You do realize that gender is determined by the male as he is the only one with the y chromosome to pass on… right? It probably has more to do with testicular temperature and stallion condition than mare condition. The mare is just a glorified crock-pot for a predetermined baby-stew. I’m sure they can find a correlation between the environment and the mare as most of them are done with the stallion in the same environment as the mare. So they are modifying both the stallion’s environment and the mare’s environment and making an inaccurate correlation. A baby can’t changes it’s genetic material to suit society, and a mare can’t produce a y chromosome out of nowhere. I’m calling BS on that study.
Anyway, as for the color genetics. It’s like flipping a coin, you have one coin and you reset your 50/50 chance every time. If you did it a million times it’d come out something around 50/50 but at 10 or so you are going to have skewed results.
You can make the square:
[table=“width: 200, class: grid, align: center”]
[tr]
[td][/td]
[td] G [/td]
[td] G [/td]
[/tr]
[tr]
[td] G [/td]
[td] GG [/td]
[td] GG [/td]
[/tr]
[tr]
[td] g [/td]
[td] Gg [/td]
[td] Gg [/td]
[/tr]
[/table]
This is not the same thing with gender. There are many environmental factors that can effect what stallions are producing. Some are prolific stallion sires and some are prolific broodmare sires and will produce somewhere around 65% of one gender over the other due to environment (feed, exercise, living conditions, geographical location, temperature, etc).
^^^ yes I am aware of how that works. But the genes have mechanics to how they are expressed. The mares body may be selective in sex determination. They have not figured out the mechanics of it yet.
Deer have the capability to determine twins or singles depending on resource availability and some species even control the sex ratio of the population based on environmental factors. And as far as the grey, there may be reasons why a mare may or may not be ABLE to throw the expected frequency. The eye color link was an example of how dominates may be overcome by other factors.
More interesting links that show there are factors that can effects the “rules”
http://www.nature.com/scitable/topicpage/barbara-mcclintock-and-the-discovery-of-jumping-34083
http://83.149.228.85/fundecology/behaviour/CAMERON1_et_al_1999a.pdf - Trivers–Willard hypothesis
This is interesting and not the same mechanics as how a horse would select but shows how populations adapt to their environmental changes. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC44426/pdf/pnas01138-0116.pdf
One more link that goes a bit beyond a Punnett square in terms of explaining why you might get different results than anticipated: http://en.wikipedia.org/wiki/Epigenetics
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy…
In terms of gender, there are theories that environmental factors (like whether the mare is gaining or losing weight at the time of conception) may alter something in the mare’s repro tract (like pH) that is more favorable to “X” sperm or “Y” sperm.
As for the stallion being responsible for a variation in sex ratio’s due to his conditions, this would be very easy to test. To have statistically significant results in offspring, a stallions gametes would have to have very skewed ratios. That would be easy to find as all you would have to do was change the conditions of the stallion and count the results.
Now this would have HUGE implications for reproductive industry if you could significantly influence the sex of the offspring by keeping the stallion warmer or cooler. People pay a ton for that service now and it is expensive and not reliable. So I do not think that is a factor.
Study on sex ratio relating to mare’s body condition at time of conception: http://biolo.bg.fcen.uba.ar/eyca/Seminarios2/Seminario28.pdf
I bred my grey TB mare (http://www.pedigreequery.com/kourages+kelly) to a grey stallion (Riverman). I know the stallion is not heterozygous for grey…and it looks like my mare COULD be but I don’t know and don’t care enough to test.
So she has at least a 75% chance of producing a gray foal. I’ve already been joking that knowning my luck…I’ll STILL end up with a chestnut filly!
I bred a dark brown mare to a black stallion…and ended up with a Chestnut filly so my mares already seem very prone to try and buck the odds 
OP–good luck to you. If I get a grey filly and you get a black one…we could always trade Granted with Gabsy, yours may be much more ammy friendly than mine will likely be! I bred my cross for an UL event horse…Riverman’s can be tough as youngsters but my mare has a great mind and temperment (raced for 7 years and still easy to work with her).
[QUOTE=bornfreenowexpensive;7820653]
I bred my grey TB mare (http://www.pedigreequery.com/kourages+kelly) to a grey stallion (Riverman). I know the stallion is not heterozygous for grey…and it looks like my mare COULD be but I don’t know and don’t care enough to test.
So she has at least a 75% chance of producing a gray foal. I’ve already been joking that knowning my luck…I’ll STILL end up with a chestnut filly!
I bred a dark brown mare to a black stallion…and ended up with a Chestnut filly so my mares already seem very prone to try and buck the odds
OP–good luck to you. If I get a grey filly and you get a black one…we could always trade Granted with Gabsy, yours may be much more ammy friendly than mine will likely be! I bred my cross for an UL event horse…Riverman’s can be tough as youngsters but my mare has a great mind and temperment (raced for 7 years and still easy to work with her).[/QUOTE]
Haha we can talk when we see what we get ;). I’m currently riding a Gatsby mare who is out of a sassy OTTB prelim event mare and she seems to have quite the right ingredients for an upper level eventer. So hopefully this one out of my also sassy OTTB event mare (who would have gone prelim had back injuries not thwarted our plans), feels the same way! But you’re right, the Gatsby babies tend to be very ammy friendly! But I’m up for a challenge, and wouldn’t turn down a Riverman upper level event prospect either
