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#34487 - 08/15/02 12:43 PM Bantamising a breed
Rob Offline
Ruler of the Roost

Registered: 07/16/02
Posts: 783
Loc: Pennsylvania
I have come across an interesting post on rare breeds forum. This is new to me and would like to know more about it. To bantamise a breed hatch from the small pullet eggs and other small eggs , after 4-5 generations the results will be 25% of the original P stock. I originally thiught that this may cause a decrease in vigor, but why would that be the case? The eggs are not from sickly birds or inbred, of otherwise inferior. But , wouldnt the genetics of the (P) fowl dictate that the offspring would grow to normal size for the breed? I have tried to hatch from the largest eggs, in an inbred flock to help keep the size from decreasing and the results of that are the birds are actually a bit large for the breed standards. rob

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#34488 - 08/15/02 02:06 PM Re: Bantamising a breed
D. Caveny Offline
Ruler of the Roost

Registered: 07/16/02
Posts: 1102
Loc: Arizona
How does the ad go? "Sorry Charlie Starkist wants tunas which taste good, not tunas with good taste!" You have been the victim of a wives' tale. Genetics determines the mature size of fowl. If you will remember the fowl starts laying small eggs around 18 to 23 weeks of age and by 36 to 40 weeks is up pretty to good egg weight..later on they increase slightly. You can set the pullet eggs or the later eggs but they still have the same genes. Body weight is decently heritable but it still involves several genes not just a simple Mendelian recessive. The 2 dwarf genes autosomal dwarf (adw) and sex-linked dwarf (dw) will only bring down mature body weight about 30% each. In order to bantamize a line you will have to make at least 4 or 5 back crosses to bantams to select for genes for body size. Note you will need to hatch about 100 or so offspring each generation inorder to have a large enough number of gene recombinations to select downward with any rapidity. Maw did some work in that area in the 30's and I think it is mentioned in either Jull or Hutt. There is also a rather secretive fellow in Australia named Bill Stanhope who claims he can bantamize in about 3 crosses. You will also have to select individuals in each generation which have the traits of the breed you are trying to bantamize. Good luck sounds like a tedious project at best.

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#34489 - 08/15/02 05:41 PM Re: Bantamising a breed
Rob Offline
Ruler of the Roost

Registered: 07/16/02
Posts: 783
Loc: Pennsylvania
Thankyou Caveny. I really am no victim as I had doubts of this being so. But I do feel that by selecting my large eggs to set, I am going the right way. It should increase my overall egg size.And, generally, the larger birds are producing the larger eggs. Not always tho. What would be your opinion on using blk. rosecomb bantams to decrrease the size of my blk. hamburgs. I considered the rc. leghorn but the rc bantam seems to me the best route. It would be mainly the length of back and tail set to select for other than size.

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#34490 - 08/15/02 07:14 PM Re: Bantamising a breed
D. Caveny Offline
Ruler of the Roost

Registered: 07/16/02
Posts: 1102
Loc: Arizona
The method should work....you will need to select them by mature body weight and the select egg size after mature body weight. There is always variability of mature body weight in a population and there is some variation within a population for egg size. During the early part of the 20th century when breeders were interested in egg numbers they selected for numbers at the expense of egg size. Later they used truncated selection and selected for egg numbers with a minimum size of eggs. If you ever run across the Mt Hope Farms journals from the late 20's into the 30's...Goodale spent a good deal of effort doing just that. His efforts are all very carefully recorded in those publications.

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#34491 - 08/15/02 11:56 PM Re: Bantamising a breed
Rog Offline
Ruler of the Roost

Registered: 07/17/02
Posts: 775
Loc: Missouri
Guys I`m not real smart on this. But it looks to me if you want to breed a bantam from a large bird this would work. Get the most inbred birds you can. It`s a known fact that inbreeding is the best way to loose size. Plus fertility and laying qualitys. So you have 1 thing going your way and 2 things that don`t. I would get at least 4 lines going. Brother to sister will get you the size down the quickest. But you will loose the laying qualitys and fertility the quickest also. So I would use Dad to pullets and hens to sons. So if you had 4 pens going from the same birds you could cross those pens after 3 or 4 generations. Like the good breeders say. Select, Select, Select. And with some breeds you need to keep all the chicks until they are 7 or 8 months old until you know what you have. It can be a long time thing. Good luck Rog
_________________________
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#34492 - 08/16/02 05:40 AM Re: Bantamising a breed
Anonymous
Unregistered


Adult size is one of those polygenic traits, like laying characteristics. As was mentioned, there are sex-linked dwarfing genes that often show dose effects and even one of the dwarfing genes is referred to as a 'bantam' gene Gene Tables from Online Genetics . But, there is variability within populations that is not due to dwarfing genes but more likely due to subtile factors such as minor differences in the serum levels of growth hormones and other biochemical aspects.

At present and without any objective data, I can't believe that the egg size from non-bantams can have anything to do with the adult size of progeny for reasons that Caveny stated. Personally, I prefer to hatch eggs of moderate size (not too small and not too large) - my experience is that these moderately sized eggs, in addition to usually having shells of better quality, give chicks that are more active, alert and more likely to thrive. I have hatched jumbo eggs from older hens particularly when working on a trait such as disease resistance (older hens have lived longer and have demonstrated their disease resistance), but the chicks that hatch out are also large and lethargic and cumbersome.

Some people probably believe that egg size has an effect on adult size because the converse is true: small birds lay small eggs - . But, small eggs don't mean small adults - the genes determine that.

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#34493 - 08/16/02 07:34 AM Re: Bantamising a breed
R. Okimoto Offline
Lord of the Fowl

Registered: 07/18/02
Posts: 1498
Loc: Arkansas
There is a high correlation between larger chicks and faster initial growth, but there isn't a good correlation between chick size at hatch and adult body weight. In a population, chicks that hatch out of smaller eggs usually have a lower initial growth rate, but they grow as large as the average in the population for adult weight. Runts are the exceptions because of genetic defects or disease.

Egg size is correlated with body weight, but different genes affect these traits. You would probably do well to select for smaller egg size when creating bantams, not for adult size, but for viability. Small Leghorns that lay large eggs have problems with prolapse and cannibalism that this causes. Selecting for small body weight will decrease egg size too, but sometimes not enough.

We don't really know why inbreeding affects traits like body weight and egg size. The idea is that inbreeding fixes detrimental genes in your flock that may have nothing to do with body weight or egg size, but cause the bird to be more susceptable to environmental influences like disease, temperature, etc that prevent the bird from reaching its genetic potential. Everyone agrees that environment has a lot to do with traits like body size. You just have to look at the size difference between identical twins where one did not have as good a placental location in the womb and got short changed compared to the other. They have the same genes, but one was stunted by its environment.

You can breed healthy bantam stock without inbreeding. The fastest methods that take the least birds involve inbreeding, but you have to expect to fail with some lines.

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#34494 - 08/16/02 07:57 AM Re: Bantamising a breed
D. Caveny Offline
Ruler of the Roost

Registered: 07/16/02
Posts: 1102
Loc: Arizona
I have to agree with Ron on inbreeding (and of course the rest of his comment). When DeKalb started their inbreding of fowl in the 1940's they used 25,000 pairs of bro x sis matings. 2 years later they had 250 pairs that were only 75% inbred. This illustrates how many undesireable traits had shown themselves and been eliminated. Any time there is inbreeding individuals become more homozygous for traits and the bad ones effect viability or fitness to a great degree. My opinion is that inbreeding is a hocus that was championed early last century in an attempt to increase differences of lines prior to crossing in an attempt to maximize heterosis when the lines were crossed. Work in the last half of the 20th century illustrated that good nickability (and viability) could be had when lines were minimally inbred. The object of the breeder should be to maximize opportunity to select NOT minimize it so I would STRONGLY advise against inbreeding any more than absolutely necessary. Large numbers also offer a greater possibility of the occurance of desireable individuals appearing. Therefore one should hatch all the chicks they can and cull them very diligently prior to selecting breeders for the next generation. This of course implies that the breeder knows how to identify the traits not only phenotypically but also genetically during the culling process.

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