Inbreeding Depression

[Guest Cawdy]

ive been trying to do a bit of research into the causes of inbreeding depression and how it relates to pigeons. ive seen it happen before in animals that are selected on there physical appearance and when the good genes are passed that cause the appearance that you are looking for there are also recessive genes passed on that cause a negative effect when homozygous if we then inbreed the likely hood of these genes becoming homozygous is increased

 

back to the point if we as pigeon fanciers are selecting for birds that are fitter healthier and can fly faster and longer. are we not breeding away from (even when inbreeding) the the genes that cause inbreeding depression. if you only breed from the consistent winners within your strain and remove young from the gene pool that are not fit and healthy and then again only breed from consistent winner within your strain. surely the genes that allow these pigeons to be winners are the opposite of the ones that cause depression

 

yet i still here people talking about weedy inbreeds. i know that the point where people have removed the majority of all the bad genes from there strain takes years of careful breeding but surely there are some that have.

 

 

im just trying to put what experience i have of inbreeding depression and put it into a pigeon context so any info or comments are appreciated

 

thanks

Alan

[Michael J Burden]

Cawdy, I had some birds back from David Fox of Bakewell a few years back. I was notg impressed witht he in breeding he had done, I had already inbreed a lot with the family. I raced the birds and hey they surprised me by flying really well up to 660 miles!!! I do not worry about it now adays and think of hybrid vigour by outcrossing at every pairing if possible but I dont mind too if related.

atb

[Guest Cawdy]

personaly im in favor of inbreeding and linebreeding.

 

but basically what i am asking is if we are selecting for fit healthy birds , that can win races within our given line why dose inbreeding depression still occur to such a degree

 

i can see how it my affect show animals where fitness and health are secondary to conformation and appearance

but if the selection process in a breeding program is for fitness and health. and the main symptoms of the depression if loss of vitality, fitness and health then should this not counteract this ?

[Guest IB]

Random selection from only 50% of the gene pool available in each pigeon ensures that there are perhaps thousands of different gene combinations in each new sperm cell / egg cell the bird creates.

 

So as every new pigeon conceived is a unique combination of genes, IMO its very difficult and perhaps impossible to 'breed out' specific genes as you suggest.

 

Difficult subject to explain and I certainly can't explain it any better than Prof Anker does in this extract from his book:-

 

Inbreeding will still produce variation

 

We return to the theme: "brothers and sisters are often completely different. Why?†When we mate a very good pigeon with his own daughter, each youngster receives its own unique set of chromosomes, half from the father and half from the mother (which is at the same time daughter of the same father). The hen's chromosome set consists of 50% inherited from her father, and 50% inherited from her mother. Reduction division selects these genes randomly and so guarantees infinite variation in each egg cell. Which combinations will end up in the hen’s egg cells cannot be predetermined and it is exactly the same with the chromosome set in the cock’s sex cell. The indefinable variation produced by the reduction division stage explains the difference between brothers and sisters.

 

Assume in a father-daughter mating that the father makes a 50% gene contribution. If his daughter’s egg cell contains more than 50% of her chromosomes inherited from him, there will be a strong inbreeding depression in the youngster. If his daughter’s egg cell contains less than 50% of her chromosomes inherited from him, the youngster will be ‘less’ inbred but have more vitality. So it is possible within the same nest to have a strongly depressed homogeneous youngster growing up next to a very vigorous, heterogeneous youngster even although both have exactly the same pedigree.

 

Where the father passes-on the same average %, it then depends on the mother’s reduction division. In brothers and sisters, we must always take the variability of the chromosome set into account. We meet tens of brothers and sisters of famous pigeons in the sales lists. They might come from the same parents, but that doesn’t mean that they have the same valuable genes as their famous sibling.

[Guest Owen]

I reckon that inbreeding is one of the biggest red herrings in the sport. OK if you want to breed creatures or plants to conform to a specific standard that you can measure or see, then it is becomes an essential part of the breeding techniques you will want to use. However, when we are trying to breed for preformance then the whole thing becomes a wast of precious time. The one and only way that the value of a racing pigeon can be measured is through the basket, either by testing it's offspring or by testing the individuals. Then there are problems with working out what is a fair test. Most race programmes are very variable in their distances and routes. Then there is the weather which can vary enormously here in Britain. My own pigeons rarely do well on blow homes and there are others that are great at winning in following winds, and obviously the wind direction and speed can and does change all the time. So, in terms of measuring performance, there is a real problem. Then there are the numbers that are required to carry out a programme of scientific inbreeding, because to do it properly, progeny testing is part of the essential discipline, and to do do it properly tests would have to be carried out to aid selection to make progess in the chosen direction. To be practical large numbers of pigeons would be required unless of course the breeder abandons measurement in favour of luck.

In the real World the Fanciers will try out various combinations of pairings, some of which will be based on inbreeding, but most great pigeons come from outcrosses. Just ask the Belgium Greats.

I have found that the best and quickest progress can and should be made by abandoning the practise of breeding from everything in the loft and by only breeding from birds that have proven themselves. At the end of the day it is all about selection which is based on the competition and route that the birds have to deal with. I am convinced that birds that fly well in one area do not do as well in a new location.

[chaz]

In my opinion if you want to inbreed you must be prepared to race hard and cull hard as well, any inferior young birds should be removed from day one and culling should continue right through until you are happy that you only have left the birds that conform to "your" standard and then race them week in and week out as young birds, then once the season is over cull again anything that`s performances were not up to scratch.

 

I have had good success in the past when inbreeding and it will certainly breed pigeons to a type, and will allow you to cross and use the F1 crosses as race birds with hybrid vigour then blend the best back in to the family and start all over again .......

 

But then surely whatever breeding method you use this should be the selection criteria!