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#1 2011-11-19 18:38:33

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Hybrid Vigor

I couldn't resist starting some further discussion on hybrid vigor but I didn't want to hijack the other thread!

In reference to crossing two different breeds of chickens (example silkies and EOs) and calling it Hybrid Vigor when the offspring are more robust than either of the parent ipf said:

hybrid vigour. . . or the removal of inbreeding depression? Many folks reserve the term "hybrid vigour" for crosses between things more distantly related than two breeds of chickens.

I would have agreed with Island Girl's use of the term hybrid vigor. Realizing with poultry we are not crossing two different species I would still refer to this as hybrid vigor.

Some definitions from various sources:

Merriam Webster online dictionary (http://www.merriam-webster.com/dictiona … id%20vigor)
Hybrid Vigor: heterosis

Wikipedia (http://en.wikipedia.org/wiki/Heterosis)
Heterosis, or hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring. The adjective derived from heterosis is heterotic.
Heterosis is the occurrence of a superior offspring from mixing the genetic contributions of its parents. These effects can be due to Mendelian or non-Mendelian inheritance.
Within poultry, sex-linked genes have been used to create hybrids in which males and females can be sorted at one day old by color. Specific genes used for this are genes for barring and wing feather growth. Crosses of this sort create what are sold as Black Sex-links, Red Sex-links, and various other crosses that are known by trade names.
Commercial broilers are produced by crossing different strains of White Rocks and White Cornish, the Cornish providing a large frame and the Rocks providing the fast rate of gain. The hybrid vigor produced allows the production of uniform birds with a marketable carcass at 6–9 weeks of age.
Likewise, hybrids between different strains of White Leghorn are used to produce laying flocks that provide the majority white eggs for sale in the United States.

Hutt, Genetics of the Fowl (pg 552-553)
Heterosis. Synonymous with hybrid vigor.

Hybrid Vigor. The extra vigor, exceeding that of their parent stocks, frequently shown by the hybrids from the crossing of such genetically dissimilar parents as different species, breeds, strains, or inbred lines. It may be expressed as more rapid growth, larger size, greater viability, or therwise.

Last edited by poplar girl (2011-11-19 19:04:17)


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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2011-11-19 18:38:33

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#2 2011-11-19 19:40:44

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Hybrid Vigor

Sorry, didn't mean to start an argument, just pointing out that there are different degrees or relationship, and that some (note I didn't say "all" or "experts") reserve the term hybrid vigour for things more distantly related. I admit it varies among branches of genetics - for example, maize breeders would agree with you, and call a cross between two inbred lines a hybrid; forest geneticists would generally reserve the term for an interspecific, or at least inter-provenance, cross.

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#3 2011-11-19 20:14:47

poplar girl
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From: Athabasca, AB, Canada
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Posts: 3159

Re: Hybrid Vigor

You didn't start an argument ipf, I was hoping for some discussion! I recently had a discussion about this at work (in relation to tree breeding no less!) so have put some thought into my stance on this subject =D

I would agree that use of the term varies quite a bit but for domesticated livestock and plants generally you can use it for crosses made within species and even between inbred lines as you said.

Plus I thought it was a good definition to add to our list.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#4 2011-11-19 20:18:31

Susan
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From: Saskatoon, Sask, Canada
Registered: 2011-06-28
Posts: 2540

Re: Hybrid Vigor

Don't worry ipf,m she's not upset, just wanting to learn :) that's what's so wonderful about this site- we actually discuss things. We may not always agree but tempers and drama just don't seem to exist here. I love it!  I also use the term, so am interested in this thread. So its safe tosay then, we are using the term correctly then, when dealing with poultry?

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#5 2011-11-19 20:19:52

Susan
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From: Saskatoon, Sask, Canada
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Posts: 2540

Re: Hybrid Vigor

Oops- guess we were posting at the same time PG!

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#6 2011-11-20 01:09:19

nuthatch333
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From: Red Deer, Alberta
Registered: 2011-11-15
Posts: 29

Re: Hybrid Vigor

This is a great topic.
I have always thought of hybrid vigor as crosses between breeds. In dogs hybrid vigour is often shown when two inbred lines or breeds, are cross bred. I guess the degree of difference determines the value added in regards to vigor.
But please correct me if I am wrong but isn't it the case that when different species are inter-bred ie horses and donkeys you  may get a very healthy very strong hybrid but more often than not the offspring of this type of cross is sterile.
So in poultry crosses between breeds would result in additional vigor but a cross between say a guinea and a chicken may result in an interesting but sterile offspring. Along the same line a cross between similar breeds say a wyandotte and a chantecler may not produce the same hybrid vigor as a cross between, maybe a EO and a bird not closely related to its parent breeds.
Again along the same lines if a inter species hybrid is fertile and breeds back to one or both the its  parent breeds one could expect a significant degree of hybrid vigour and if it is successfull may produce an new species or may enhance one or both parent species.
Isn't mother nature great :goodthread:

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#7 2011-11-20 01:29:53

poplar girl
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From: Athabasca, AB, Canada
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Posts: 3159

Re: Hybrid Vigor

The definition of a species if I remember correctly is (in my own words) one that cannot or will not breed with another and produce offspring cabable of reproducing. So some times, like in the case of horses and donkeys, the offspring are sterile. Sometimes it is geographic or other forms of isolation that define the species. So for example, an ocean may mean that two types of birds that can successfully mate and produce offspring capable of sexual reproduction will not breed under normal circumstances and thus develop distinct characteristics over time and are classified as two different species.

I am not sure where the most benefit from crossing different breeds of chickens would be expected to come from...that is a good question that perhaps others can help answer!

Last edited by poplar girl (2011-11-20 01:30:38)


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#8 2011-11-20 02:01:59

Susan
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From: Saskatoon, Sask, Canada
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Posts: 2540

Re: Hybrid Vigor

Well look at Monika's hatch. The ones that made are not the purebreds, but hybrids.

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#9 2011-11-20 12:53:33

skeffling lavender farm
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From: Wiarton, ON, Canada
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Re: Hybrid Vigor

Interesting and Susan those breed were about as different as you could get in the chicken world, standard v's bantam, 4 V's 5 toes, fluff v's feathers...it's  a wonder they recognised each other to breed! :chook:  The term "hybrid vigor"  crossed my mind when MV popped up too and other pre EOs didntl hatch when I shipped one SumatraxEO egg in the batch to poor Monika

We saw vigour in the offspring when "crossing" McMurrays SG dorkings with the 70 year line bred Dorkings.  Vigour in a dorking is very easy to spot as the are usually a weaker chick!  It sounds like ti can be applied to any genetically dissimilar groups.  I took population genetics in Uni many moons ago and the term was reserved for cross species breeding is I remember rightly....:huh: long time ago.

Maybe in natural wild population genetics, it takes so long to get any major genetic drift or distance.  But in poultry breeding and any livestock for that matter it can happen very quickly in a few short years with heavy selection and selective pressure.  With us picking and choosing, also the ratio of say 1 roo with 10 hens would speed it up too IMO.  That's maybe why the term hybrid vigor is named and used in these situations as well.

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#10 2011-11-21 06:47:13

Skylinepoultry
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From: Old Fort, Tennessee
Registered: 2011-06-30
Posts: 222
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Re: Hybrid Vigor

So let me get this straight? Now I'm getting confused. So which one are you saying is Hybrid Vigor----
--EO X Orpington= Hybrid Vigor
                   Or
--EO X Old line EO= Hybrid Vigor
                   Or
--Guinea X Chicken= Hybrid Vigor

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#11 2011-11-21 12:28:47

poplar girl
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From: Athabasca, AB, Canada
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Posts: 3159

Re: Hybrid Vigor

All of them COULD result in hybrid vigor. In the case of the EO as long as your example is of two different inbred lines of less related EOs being crossed. There are quite a few different things that cause hybrid vigor. 

But there is no guarantee that the offspring will have hybrid vigor. For certain traits they may not be better. Or the offspring may have more undesirable traits that do not affect vigor but are not desirable for the breed. Like maybe the hybrid's feather color will be undesirable but good egg production. Or some aspects of vigor will be worse, some better, for example the guinea chicken may be super healthy but it may be sterile and unable to produce offspring, obviously for that trait it is less vigorous.

I am no expert, just my thoughts.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#12 2011-11-21 16:22:10

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Hybrid Vigor

Not all crosses result in hybrid vigour (HV), and HV is just that - "vigour". It generally applies to traits such as fertility, growth rate, disease resistances (sometimes), and other traits we think of as related to survivability. These clearly do NOT include feather colour traits, and minor points of confirmation, which are unlikely to be improved. And, as PG points out, in wide interspecific crosses, the offspring may even be sterile.

I was thinking about this as I lay awake last night, and realised that the reason I don't like to use the term for crosses between individuals of the same species is that, in these crosses, HV isn't a "real" thing - IMO, it's really just the absence of inbreeding depression.

Last edited by ipf (2011-11-21 17:59:39)

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#13 2011-11-21 16:34:37

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Hybrid Vigor

One problem is that, when you first start looking at these concepts (e.g. species, hybrids, inbreeding) it all seems quite clear, or at least quite well defined. Take species, for example.

The classic definition  of species is a “group of organisms capable of interbreeding and producing fertile offspring”.
This is useful only to a point; it gets grey and fuzzy in the corners. Generally we think that members of the same species mate and produce fertile offspring, while individuals from different species do not. But there can be many different reasons for the non-production of fertile offspring. Genetic incompatibility (different numbers of chromosomes, vastly different arrangement of genes on these chromosomes, etc) is only one. Other reasons why things do or don't mate, when we wouldn't or would expect them to, on the basis of species assignment, include  geographic separation or barriers (distance, or high mountain ranges), size (like toy poodles and great danes, or even Australorps and small bantams), mating displays (as in many birds), pollination mechanisms (many flowering plants, such as orchids), timing of gamete availability and receptivity (many trees) – it goes on and on. If we use artificial insemination or pollination, or physically move individuals around, or they wander on their own, all sorts of species “barriers” fall very flat.

One of my favourite species conundrums is that of “ring species”. The classic text book case is that of the circumpolar gulls. Starting with the herring gull in the UK, and moving west at about the same latitude, there are a number (6 or 7?) of slightly different gulls, each with different names, but each interfertile (and interbreeding happily) with the one to the east and the one to the west. Keep going far enough, and you come back to where you started, except that the birds you end up at aren’t herring gulls at all, they’re lesser black-backed gulls, which don’t even give the herring gull a flirtatious glance, much less mate with it! ! So, what’s the species here?

People thought up the concept of species (and genus, family, order, etc) to help explain and categorise observed variation into a logical hierarchy. Trouble with a lot of concepts is that we humans like to quantize, or "round" in the mathematical sense, to the nearest whole idea or unit (e.g. species), while many natural phenomena are continuous in nature.

This quantization sometimes gives surprises. The two numbers 3.4999999 and 3. 5000001 are very close together indeed (<<1/100 of 1%), but if you round them to the nearest integer, they come out 3 and 4.

Last edited by ipf (2011-11-21 16:42:12)

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#14 2011-11-21 18:59:57

nuthatch333
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From: Red Deer, Alberta
Registered: 2011-11-15
Posts: 29

Re: Hybrid Vigor

ipf wrote:

HV isn't a "real" thing - IMO, it's really just the absence of inbreeding depression.

I think ipf hit on the real Crux of the topic right there.
As breeders of purebred birds we are always struggling with the size of the gene pool we have to work with. This topic gets talked about on all forums and there seems to be two very different points of view.
Those that maintain a closed flock, and those that feel the occasional out-cross will improve the general vigor of the flock.
The proponents of the closed flock feel introducing traits from an out-cross does more harm to the flock by introducing unwanted traits than the benefit of reducing the inbreed depression. They feel that the solution is to produce large numbers of offspring and be very severe on culling the flock.
The proponents of the occasional out-cross believe that improving the vitality of the flock  by adding additional genes is more important that introducing any unwanted traits. The unwanted traits can be breed out of the flock at a later date while the benifit of the outcross remains in the flock.
They both seem to make sense to me, perhaps the determining factor for an individual breeders is their capacity to house large numbers of birds and there feeling toward severe culls.
I believe somewhere in the middle may be an optimal place to be.

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#15 2011-11-21 20:29:48

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Hybrid Vigor

Well put, Nuthatch. It comes down to balancing the "show" qualities with the "survival of the fittest" qualities, IMO.

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#16 2011-11-21 21:38:05

Young Heritage
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From: Gainesville, Georgia
Registered: 2011-06-30
Posts: 157

Re: Hybrid Vigor

ipf wrote:

Well put, Nuthatch. It comes down to balancing the "show" qualities with the "survival of the fittest" qualities, IMO.

X2  :thumbs:


FBCM and Euskal Oiloa

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#17 2011-11-22 00:39:41

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Hybrid Vigor

Very nice differentiation of "vigor" from "show" traits ipf and young heritage. Totally different and almost opposing  purposes to line breed or out cross. I agree.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#18 2011-11-22 01:14:15

ipf
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From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Hybrid Vigor

Really, guys, do read, and think about, that ring species thing. It's so interesting! They  interbreed all around the great circle (latitude line), are actually a continuum, but when they meet again after going around the circle, they are totally incompatible! There's a metaphor in there somewhere. . . .
Science is squishy, is my interp.

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#19 2011-11-22 01:36:14

poplar girl
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From: Athabasca, AB, Canada
Registered: 2011-06-30
Posts: 3159

Re: Hybrid Vigor

I read it (twice) ipf, it is a very good example of several concepts.

I can't find that metaphor you speak of though...must be my brain is going soft after too many years of moderate to light use.


Raising red cuckoo (marraduna) Euskal Oiloak and self blue (lavender) & black Belgian Bearded d'Uccles.

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#20 2011-11-22 02:47:02

skeffling lavender farm
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From: Wiarton, ON, Canada
Registered: 2011-06-17
Posts: 2720
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Re: Hybrid Vigor

That is cool, we never learned that in population genetics in 1993, I don't remember learning the term either.  Looks like it's Larus gulls, Wiki has a really good page on it
http://en.wikipedia.org/wiki/Ring_species

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#21 2011-11-22 02:57:06

ipf
Member
From: Salt Spring Island, BC, Canada
Registered: 2011-08-29
Posts: 168

Re: Hybrid Vigor

Exactly! Thanks, SLF. The ensatina salamanders (references  are in the wikipedia article) are the other wonderfully illustrative example, and really bear thinking about.

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#22 2011-11-22 03:51:09

skeffling lavender farm
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From: Wiarton, ON, Canada
Registered: 2011-06-17
Posts: 2720
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Re: Hybrid Vigor

I just read the summary, interesting whether they should be split into further species too.  I took some plant systematics in my 4th year (and loved it) and I think I am a lumper or a splitter just depending on what mood I'm in. :lol:  I mean you could split down to individuals technically!  Or lump everything together!

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