Genetic Preservation of Chocolate Turkeys with Terminator Genes

by
Paula Johnson

with permission from
SPPA Bulletin, 2002, 7(3):3-4

The following article is for a general understanding using conversational terms and is only my personal theory based on rather small flocks and is not meant as a scientific document. I have spent the last five years studying Chocolate turkeys. I haven't found much historical information on Chocolates other than they were popular in the south before the Civil War. The Civil War caused so much change in the south that the Chocolate Turkey never recovered in popularity and their numbers have been declining ever since with only a few known to exist in North America.

I received my first Chocolate poults from Glenn Drowns in late May of 1998. Three were shipped with other varieties of poults. All three poults were very healthy and grew into beautiful large adults. I ended up that first year with 1 male, which weighed about 22 lbs at 9 months and 2 hens that weighed about 13 lbs each. All of the Chocolate turkeys that I have had were well filled out in the breast and legs, but were not broad breasted to prevent natural mating. When the first eggs started coming in March of 1999, many of the eggs were fertile for the first two weeks. However, for the rest of the laying period that year none of the eggs were fertile. At first, I thought of external things that may have caused the infertility such as heat, lack of vitamins, etc. However, all of the other varieties of turkeys were still fertile and they were fed and grown under the same conditions as the Chocolate turkeys. I kept the male and hens together that summer, hoping that the fertility would return, it never did. I did manage to hatch out 4 Chocolate poults that year which resulted in 2 males and 2 females. Again, in the spring of 2000 the 2 new males were fertile for about 2 weeks and then never again were they fertile, just like their father. Realizing that I probably had a genetic reason for the infertility, I decided to outcross the hens to a fertile male soon after I started getting infertile eggs. The chocolate gene is a dilution gene on a black background color, I crossed the Chocolate hens with a large Black fertile male. All of my Chocolate hens were excellent egg layers for the first 3 years of their life. The hens started laying in late February or early March and consistently produced eggs through 100-degree weather into early August. I was excited as I was getting many fertile eggs. I kept 12 toms and the 10 hens out of the Chocolate x Black crosses. These F1 poults were all black in color with some brown at the edges of some of their feathers.

When the spring of 2001 came around, I had 4 new Chocolate males that were totally infertile; they were not even fertile for 1 day. Also, all 12 of the F1 toms were infertile from day one, not a single fertile egg. I still had 4 Chocolate hens that were laying very well, so with the understanding that White Hollands have the white gene on a black back ground color I crossed a very fertile White Holland with the 4 Chocolate hens. This White Holland tom had been with 4 White Holland hens and every egg that came out of that pen was fertile. This was the best fertility rate that I had ever experienced and if this male could not overcome the fertility terminator gene then nothing could. Therefore, I thought I would try one last hope of getting fertile males out of these 4 Chocolate hens. It was at this point that I suspected and others confirmed my suspicions that it was probably the hens that were passing on this fertility terminator gene.

In the spring and summer of 2001, I hatched out about 30 poults that were F1s of the White Holland and Chocolate cross. Expecting more black poults, I was surprised to see that most of the F1s were blue slate in color with a few solid black. The blue slate coloring was very consistent among the F1s with an equal amount of black speckling over a medium blue color. I ended up with 15 toms and 11 hens of the blue slate color, with 1 tom and 2 hens that were black in color. The Black tom was sterile. However, the blue slate colored F1 males are fertile and have continued to be fertile at the time of this writing in June 2002. I bred the F1 males with their F1 sisters and hatched a variety of colors in the F2s. I have bronze types, blue slate types (most numerous), white, light brown or tan types, solid blacks, and 2 Chocolate poults so far. I also bred two F1 fertile toms back to their Chocolate mothers, but the hens have produced very few eggs this year and the eggs they did produce were double yoked, so I have no poults from that breeding.

I have been criticized for breeding the F1 brothers to their F1 sisters due to the females possibly passing the terminator gene on to their sons. However, I wanted to prove a few things to myself. First of all, I needed to know that the F1 blues were fertile, and second, I have learned that my White Hollands are probably on a black background with the blue dilution gene thrown in because most of the F2s are slate in color. I say probably, because we do not seem to understand the Chocolate dilution factor very well and it may have an effect, but doesn't seem to have much of an effect at this time other than probably being recessive to the slate dilution gene or the Chocolates have a slate dilution gene as well in their genetic make up. I do feel positive that my Holland line is on a slate gene. Breeders often added a dilution gene to the background color of their white birds to enhance the white gene. I also believe that since the slate colored F1 males are fertile, but all of the black colored F1 males were infertile, either by the Black x Chocolate cross or the Holland x Chocolate cross, that the terminator gene may only be activated in relation with the undiluted black gene or turned off by the slate gene. I have about 6 black colored F2 poults from the F1 slate colored breeding and if any turn up to be infertile males next spring, then their infertility along with other colors not being infertile will convince me that the terminator gene is connected to the black color. Thus, if I put the dilution blue gene in the background (if it is not already there) of my Chocolates it is possible that I may be able to side step this terminator gene in my Chocolates despite breeding with terminator females. If in deed it is a fact that the Chocolate hens pass on the infertility gene to their sons then breeding with these terminator females will prove or disprove my theory of the slate gene side stepping the terminator gene. However, if the chocolate dilution gene is recessive to the slate dilution gene I may never get a fertile chocolate colored male again.

I am anxious to see what the F2 poults look like as adults as some may be light brown and auburn types. I will breed the similar colors of the F2 together as well as breed some F1 males/females and F2males/females together next year, assuming they are fertile, to further investigate this theory and maybe come up with new theories. This color/terminator theory is interesting because you do not hear much about color genes influencing more important genes, but so far there seems to be a possible connection of some sort. I am criticized sometimes for remaining too open minded and not allowing some data to be turned to "fact." I have learned that working with complicated color genetics can take a long time to prove a theory, if it can be proven at all, especially with small flocks such as mine. I cannot forget that the main reason for doing this is to have a fertile, thriving flock of Chocolates. Only time and money will tell us more. In this situation, if no fertile chocolate males show up in the next few years, this line of Chocolate turkeys is extinct.