Page 1 of 3 1 2 3 >
Topic Options
#22747 - 11/13/02 05:16 AM Inbreeding thread #2
Anonymous
Unregistered


We have recently been discussing some inbreeding problems in other threads. I post this because a lot of people are concerned about this and there are conflicting philosophies from reputable sources.

For example, Carefoot has a chapter in the Crawford book that takes the Fancier's point of view about inbreeding and argues that much of the deleterious effects of inbreeding can be selected against, if one just will. Sometimes this means not selecting for body conformation or type, but rather for livability. So the occasional 'ugly duckling' in a line might actually be a valuable resource for the trait of livability. So, one can get the sense from that, that careful inbreeding can be OK.

Other posts here (by Caveny and Ron (?)) seem to be more pessimistic on the topic of inbreeding.

In addition, Mrs. Miller's line of Jersey Giants didn't have any new blood for quite a few decades. She was able to accomplish long-term line breeding, but I don't know what her methods were (she passed away not long ago).

With little facilities, I maintain two 'lines' of layers. We use leg bands now and careful record keeping and set up our breeding pens 'by the numbers on the leg bands'. So, we know which bird belongs to which line and breeding is set up with this information in mind. I try to set up cousin-cousin matings and I will sometimes back-breed to a parent or uncle. We have only been breeding our own lines for a small number of years (3?). But still, the males I am using are not completely unrelated either. Which brings up another topic - how long do two lines have to be maintained in isolation from each other before they are considered to be unrelated? For example, two 'cousin lines' will still be cousin lines in 100 years even if maintained in isolation. I believe, to answer this question, one has to know the rate of mutation of the genes themselves.

Other breeders, I am certain, have highly inbred lines. I am aware of highly inbred lines in Araucana fowl, for example, which are already hard to breed because of Et and Rp effects. Some of these breeders have expressed concerns about further inbreeding depression and others have opinions more like Carefoot's that careful inbreeding can be accomplished.

There isn't really a question here - just the comment that I don't feel that there is a real consensus about inbreeding.

Top
#22748 - 11/13/02 09:03 AM Re: Inbreeding thread #2
CJR Online   content
Coop Master

Registered: 07/16/02
Posts: 8483
Loc: Montana
Leee, Inbreeding as well as any breeding of poultry can be an intentional method of obtaining any trait you want to be more reliably dominant, and also the opportunity to drop appearance of traits that are not desired. In flock breeding, this has to be a mob- scene to control and evaluate. It is also easy to do in small numbers, by matings with birds of known breeding. I say known, because we still cannot see the whole spectrum of heredity.

I have inbred, first father/daughter, then brother/ sisters for 3 more generations in a row, selecting and going on ONLY with the brothers and sisters that had, in my plan, the color and body shapes I wished. Since they developed normally, produced normally, I lost no chicks (only set a manageable few) This was 10 years ago and birds from these breedings, now can be mated with chosen compatible lines after those initial inbreeding sessions. I have kept some of those birds, still producing (none of those early birds were vaccinated for Marek's, as all the birds hatched in the last 4 years, have been.) None have been lost to Marek's, which is no credit to inbreeding (in all probability). I keep this line (now only hens, setters, and producers of the variety I worked with), as an outcross line to my closely linebred birds and mate and hatch from them at intervals. The line has produced good males, but I sold the last one a year ago--have a daughter--as I keep SMALL numbers of birds. (And, darn it, old age is encouraging me to keep smaller numbers each year.) Because I know each bird individually, have records of each back to my first birds, I have sorted out the best for, temperament, productivity, and for me the bottom line is SHOW quality. Several of these hens are in at least 1/2 of my best breeding birds of the last generation. You can have it all--and inbreeding may be a good tool. Every egg is dated and marked with parents #s, every chick is marked, variety is also recorded and right now I am working with the pages of the pedigrees of the birds that will be used for hatching the next generation. The occasional "surprise" variety in a chick is no mutation--I can find it in the pedigree of the chick's pedigree. Once there, it is always there, but diluted to be ineffective until one of my matings brings it forward again. I have birds of one variety that I know can reliably produce as many as 4 varieties, with chosen mates from different lines. And this year, I "recreated" a great bird that I lost to Marek's by using two birds sired by his grandsire, but neither was his recessive variety. He is winning in the midwest this year! It was a planned breeding that was successful because I knew the breeding of the birds--not the longshot, still was lucky that I did not have to hatch large numbers. I would never be afraid of inbreeding in perpetuity (or however long that may be), as long as I had no regrets over discarding any bird not meeting fertility and production scores. There ARE occasional pullets that are not good producers (but that happens in all flocks). Selection and records is the name of the inbreeding game. And my birds are mostly (never will be perfect nor peas in a pod) top quality, very few culls, almost no substandard birds. And I do not use culls, but sometimes breed a slightly substandard bird that has one or more outstanding features--as keeping the roulet wheel going is good business! CJR

Top
#22749 - 11/13/02 09:35 AM Re: Inbreeding thread #2
Anonymous
Unregistered


Thank you, CJR... I was thinking of you too when I posted about Mrs. Miller's line. I know you have a famous line of Dutch Bantams. My point is that it is possible to manage inbred lines. There are people out there who disdain all inbreeding and many novices will follow their advice.

Top
#22750 - 11/13/02 09:44 AM Re: Inbreeding thread #2
Rob Offline
Ruler of the Roost

Registered: 07/16/02
Posts: 783
Loc: Pennsylvania
I am in agreement with CJR. I have always used some form of inbreeding in all my animals. Some species seem to handle closer breeding than others. My line of gundog beagles was very vlosely bred and very predictrable in all characteristics. Very few gealth problems. The line of hamburg chickens I am working with have been inbred for over 35 years. I can not locate a flock in the US that didnt originate form my source of brood stock. Thats not to say someone hasnt use a Minorca or a Leghorn somewhere down the line. But as Jean says, close breeding requires good records and a lot of study. My opinion is that the fancier speaks in terms of reality or neccesity, whereas someone like Ron speaks as a scientist. I do feel my birds need a infusion of some new blood. But I dont want to go to a total outcross so will have to find a related cock of another variety in the same breed, which was created with the genetics of my birds parent stock. The best Beagle I ever had, had the same sire in the 7 generation pedigree over a dozen times. I have always considered inbreeding as sib x sib; sire x daughter; dam x son. Linebreeding is breeding within the family or line. I do know that some of my very best animals are from 1/2 sib matings. And I have used terminal sires to create pure show stock not intended for breeding.

Top
#22751 - 11/13/02 10:00 AM Re: Inbreeding thread #2
Nancy Offline
Flock Leader

Registered: 08/12/02
Posts: 315
Loc: Michigan
I too would like to thank you, as I am a novice and believed that they couldn't be inbreed.
My breeding project for the sping was turning out to be most difficult as I have found only one breeder of the chickens I want to breed. I was searching and searching for another breeder to get the rooster from. This has helped me tremendiously. Thank you both so much!!
Nancy
_________________________
Nancy

Top
#22752 - 11/13/02 10:16 AM Re: Inbreeding thread #2
Anonymous
Unregistered


P.S. Does anyone know Carefoot's e-mail address? We should try to get his participation here.

Top
#22753 - 11/13/02 11:23 AM Re: Inbreeding thread #2
R. Okimoto Offline
Lord of the Fowl

Registered: 07/18/02
Posts: 1498
Loc: Arkansas
Inbreeding is done all the time, but you take your chances. Selection against inbreeding depression takes raising a lot of birds and breeding them and then only selecting breeders from the best producing matings. Most backyard breeders can't do this and still select for what they want because they can't raise enough birds and make enough matings to accomplish anything useful. The closer you inbreed (Parent to offspring or full sibs is the worst) the more likely you are to run into problems. This just happens because just by chance you have a high probability of fixing detrimental genes in your line. When you line breed a male to his daughters and granddaughters you not only increase the desired genes of that sire in your line, but you also increase all the recessive bad genes that he carries too. If the male carries too many bad genes your lines viability goes down noticably. If you get lucky nothing much happens, but you have to get lucky because the average genetic load (a measure of the number of lethal equivalents in an average chickens genome) is around 6 for chickens. This is pretty high and your chance of increasing these recessives and producing homozygotes goes up dramatically when you line breed.

The real problem comes in because most of the detrimental genes that a chicken carries are not fully lethal as homozygotes. When they are homozygous they only decrease the viability a little. So you can fix these alleles in your line by accident by inbreeding. The birds aren't dead, but they are weakened. If you accumulate too many of these detrimentals your line dies out.

Quail are even worse than chickens for inbreeding problems (genetic load of 8). I wanted to create an inbred line of quail for research purposes so I took two random bred lines that were pretty much unrelated, but had derived from the original Coturnix stocks brought to America (one was the E (brown) line and the other was wild-type). I took 5 sires from each line and mated them to females from the other line and then tried to make two backcrosses of daughters to each sire. I only came out with two sire lines out of the 10 that I started with that produced enough progeny after the second daughter mating to continue.

After 3 years of cousin matings the two lines are still going, but I am probably about to lose one of them because this generation is pretty much of a dud. Most of the chicks from this line look pretty pathetic, but the chicks from the other line look fat and happy and we raise them mixed together in brooders. You can tell the A line from our B line without looking at their bands. The only reason that I've lasted this long is that I make 12 or more cousin matings for each line and then only breed from the best 2 or 3 matings. For the last couple of generations around 30-40% of the cousin matings do not produce any live chicks.

You can select against inbreeding depression, but you have to get lucky to select against it if you are only doing a few matings. Pick the wrong breeders and you could mess up a line.

Homing pigeons are highly inbred but they seem to do fine. Some highly inbred lines of mice have been selected to be more productive than the random breds. You can select against inbreeding depression it is just that most backyard breeders do not make enough matings to effectively select against it.

Top
#22754 - 11/13/02 02:13 PM Re: Inbreeding thread #2
BC Breeder Offline
Coop Keeper

Registered: 07/16/02
Posts: 434
Loc: Canada
If a breeder's goal is to achieve a true breeding product, inbreeding is necessary, there is no escaping it. Therefore, the question isn't so much whether one should inbreed, but HOW one should inbreed. Inbreeding is a double edge sword, it's required to fix traits, but also usually leads to inbreeding depression. The task for the breeder is to get their cake and eat it too wink The breeder can't rely on chance to avoid inbreeding depression, unless he also likes his chance of winning the lottery, and therefore needs to develope a strategy that will tip the odds in his or her favour. Most fanciers are unable to do this and this is the reason the concept of outcrossing is so popular amongst fanciers. Not because it's the best approach, but because it's the safest.

Chapter 39 of Crawford's Poultry Breeding and Genetics deals with inbreeding and was written by Hans Abplanalp. I'll refer to his input to make it easier for some here to recieve my input wink

The first point he addresses is the rate of inbreeding and effective population sizes. Anyone wanting to combine success and inbreeding should study these two concepts as they are important when deciding between two or more strategies. Regardless of the breeding methods chosen, overall the breeder wants to maximize the effective population size and minimize the rate of inbreeding. This is a whole thread in itself so I will leave it there.

Hans then moves onto discussing inbreeding depression and it's management, first bringing up various examples of inbreeding success and failures. He mentioned how some successes were attributed to selecting for good hatchability. He then moves on to comparing hatchability rates of various poultry, noting that highly worked lines such as leghorns showed very little hatchability loss associated with inbreeding while less worked species such as quail and partridges suffered great loss of hatchability when inbred. Therefore, I conclude that the effectiveness of using hatchability will be determined by the previous work of the poultry line. Such a selection criteria would be more effective for someone working with the wild ancestral breeds that parented the araucanas than someone working with production leghorn genetics. The effectiveness of hatchability based selection on non commercial based fancy lines such as ameraucana, sumatras, silkies, etc is debatable and more than likely variable depending on the history of each individual line. To help us consider this, Hans goes further and mentions that the Leghorn's reduced change in hatchability wasn't due to the 30 generations of closed breeding and 30% inbreeding alone, but that the selective pressure used in each generation played a major role. The Leghorns were under the greatest selective pressure and the quail under the least. Because of the methods used by most fanciers and the way we share and outcross between lines, it's probably safe to assume that most fancier lines are the result of reduced selective pressure. But again, this will vary from line to line.

Then Hans got into some interesting results, he started associating egg production traits to inbreeding depression. Starting with the results of Ameli et al. (1988), he suggested "successful long-term selection for high egg production and reproduction may lead to reduced inbreeding depression of these traits." pg967. Cahancer et al. (1980) is a paper discussing inbreeding effects of commercial turkey breeding flocks where it was found that the sire lines suffered much higher inbreeding depression than the female lines. Selection of the female lines was based upon reproductive rates while the sire lines were based upon growth rates. Again supporting the idea that selecting for egg production also selects against inbreeding depression.

Next Hans moved onto discussing whether inbreeding depression can be removed from a population without outcrossing. He discussed one experiment where 16 seperate inbred lines were attempted for 4 consecutive full-sib generations, but only 3 survived inbreeding depression and remained viable. In that and another study, all surviving lines had the highest reproductive performance at the outset, suggesting that an inbred line must start with good reproductive rates to be able to finish with them. I assume reproductive rates is combining hatchability and egg production, but one would need to read the papers directly to confirm. They are Kuhlenkamp et al. (1973) and Sittmann et al. (1966). Kinda old references though. Then again, Hans comes back to mentioning how the effect of inbreeding on hatchability fluctuated from study to study but on egg production, it remained linear in all the studies and poultry species studied.

Han's comments on "Artificial Selection Against Inbreeding Depression" is outdated but can still serve as a place to build a conceptual foundation, IMO. He first discussed straight forward inbreeding where several fullsib lines were kept and where each line was selected for egg production. Half of the lines originated from random mated stock and half from previously inbred stock. The lines originating from random mated stock showed greater inbreeding depression at the outset but then ended up with a faster rate of improvement. as a side note, crosses between the lines showed heterosis for egg production.

He next discussed cyclic inbreeding where one or two cycles of inbreeding is followed by a cross of unrelated inbreds. And then the cycle repeated. If I am interpretting this correctly, this could be similar and/or a variation of another concept discussed here in the past, braiding the lines. If I understand the concept correctly, the breeder maintains multiple inbred lines, say numbered 1 to 4. For one example, each line starts with siblings which are crossed creating generation 2. Select gen2 cockrels are moved one line to the right, so that select cockrels from line1 are paired with select hens from line 2 and select cockrels from line 4 are paired with select hens from line1 (I'll let you fill in the blanks).) Creating the outcrossed 3rd generation. Select gen 3 cockrels are not moved and are mated with their select sisters to create the 4th generation. In the past discussions of the braiding method, I believe the inbreeding generation was omitted. However, the inbreeding generation would hasten the success or failure of the project, whichever the project is destined for.

A more current strategy that I've been reading about has also gained my interest, compensatory mating. First, one needs to differentiate between selection of breeding parents and then selection of breeding pairs, two seperate levels of selection. The above cyclic method is one way of selecting breeding pairs, but is more mathematic in principle than anything. It really doesn't account for what we observe while the compensatory method does give the breeder more discretionary control. It gives the breeder even more control in reducing inbreeding depression and directing the breeding outcomes at the same time.

The way I understand compensatory mating is that the specific traits of the breeding parents are ranked and then the breeding pairs are selected based upon opposite rankings. Therefore, an individual with a high inbreeding coefficient would be mated with one of a low inbreeding coefficient. Or say, if egg production was a selection criteria, a cockrel who's sisters had the highest average egg production would be paired with those select hens who's sisters had the lowest average production. And visa versa. Or with my specific interests, I will be ranking the egg colours as part of the selection process and use the family egg colour data to assist in the selection of the breeding pairs.

Here are some current papers that have helped teach me about inbreeding and selection methods.

Sanchez L, Toro MA, and Garcia C. 1999. Improving the efficiency of artificial selection: more selection pressure with less inbreeding. Genetics. 151:1103-1114.

Quinton M, Smith C, and Goddard ME. 1992. Comparison of selection methods at the same level of inbreeding. Journal of Animal Science. 70:1060-1067.

Caballero A, Santiago E, and Toro MA. 1996. Systems of mating to reduce inbreeding in selected populations. Animal Science. 62:431-442.

Jansen GB and Wilton JW. 1985. Selecting mating pairs with linear programming techniques. Journal of Dairy Science. 68:1302-1305

Nomura T. 1999. A mating system to reduce inbreeding in selection programmes: Theoretical basis and modification of compensatory mating. Journal of Animal Breed Genetics. 116:351-361.

**************************************************

Now I have previously mentioned the idea of incorporating egg production into our selection strategies, an idea that has been met with resistance. I assume the main reason is the logistical problem associated with tracking egg production of individual hens. However, if a breeder is serious about wanting to find success while practicing high degrees of inbreeding, such a breeder would be wise to revisit the concept and explore it further.

This is where I'm at, trying to come up with a practical method of tracking egg production. Trapnesting for a year to gain a year's worth of credible data simply isn't practical. Rate of lay is measured in several ways starting with age at onset of lay. However, environmental factors play such a huge role here that I can't see using it having any significant effect. How would the fancier effectively account for environemental factors? Another measurement is the number of eggs laid in a year, but as I said, collecting such data from free ranging chickens is problematic. One would need to be on hand to collect data and release the trapped hens several times a day. Most fanciers, myself included simply couldn't dedicate the time. A third parameter would be the number of eggs laid between days off, or the rate of lay during the actual laying period. Like I have one hen that lays about 6 eggs a week and another than lays 4 eggs a week. Some hens lay through their molt and therefore pretty much lay for the full year and others stop to molt and only lay for a portion of the year. Therefore, determining a hen's egg production value is much easier said than done. Nonetheless, that doesn't mean we shouldn't explore and discuss ways of possibly accomplishing just that.

I know I could dedicate a small number of days per month to collecting trapnest data, maybe there is a way to time the data collecting to guestimate rates of lay. Maybe taking measures during periods of low production can help us identify the better layers? Just tossing ideas. Right now, my flock is small and varied enough that I can identify and track certain specific eggs, but as my inbreeding progresses and the variability decreases, I will loose that ability.

Caveny has in the past commented that egg cholesteral levels fluctuate with rate of lay, maybe they could be used to guestimate the rate of lay of various hens? Might sound complicated at first, but in 2nd year biochem we tested for levels of various things ranging from vitamin C to caffeine with relatively simple procedures. Maybe there is a test for cholesteral that isn't out of reach for the fancier or nonchemist. We wouldn't need exact numbers, just relative amounts like egg 3 had twice as much cholesteral as egg 6. Any ideas Leee? Chasing cholesterol may lead to a dead end, but we shouldn't be afraid to explore it and verify it's impracticality before dismissing it. Ditto for the idea of tracking egg production. Who knows, we may actually discover a winning method.
_________________________
Omega Blue Farms
http://www3.telus.net/OmegaBlue/

Pictures related to my blue eggers can be viewed at:
http://groups.msn.com/BCsBlueEggers

Top
#22755 - 11/13/02 02:13 PM Re: Inbreeding thread #2
Anonymous
Unregistered


ron what other types of birds do well when inbred? this is a piece of informatoin that i have never come across. i didn't even know that about birds, all my birds are parent/sib or sib /sib

Top
#22756 - 11/13/02 03:10 PM Re: Inbreeding thread #2
Anonymous
Unregistered


Gee, Vic, don't make such long posts... it is hard to struggle though it... I don't believe most people will .

HS

Top
Page 1 of 3 1 2 3 >


Moderator:  Admin @ The Coop, Henk69