Why are hybrids chickens more prone to disease than pure breds?

[brummie]

I have often wondered why it is generally the hybrid's that are more strictly vaccinated, whilst many times pure bred's are not. I have read on a number or occasions that hybrid's tend to get ill more often and are more prone to disease than pure bred's which is why hybrids are always vaccinated?

But why is this? What is it about the hybrid genetics that makes them more prone to illness and have shorter life spans than pure breds, when a chicken after all is a chicken whether hybrid or pure bred?

I found this somewhat interesting, although I do not know how true it is.

http://www.farmforward.com/features/hybrid

 

[Fred's Hens]

The article is aimed at the CX type, fast growing broiler birds. The documentation for most of the statements is pretty weak. That site you linked has an agenda and a point of view. This makes it difficult to assess the true value of the article. This group promotes "heritage" fowl in opposition to the commercial lines.

I personally largely share the point of view, but I don't think there is a whole lot of evidence offered here.

 

[brummie]

Ok, forget that article, It was a chance article I came across when trying to find more about this issue.

But generally it seems that most people do seem to be very particular about vaccinating hybrids, but are not too fussed about pure breds. So is there a real issue with genetics or something that makes hybrids more prone to illness than pure breds or not? And why do pure breds tend to live longer?

Or is it just that because hybrids lay a lot in a shorter period of time or grow faster, this somehow weakens their immune system?

I just can't seem to get it out of my head that hybrids are somehow "processed" or "genetically manufactured" chickens, which is why they have these side effects.

 

[Fred's Hens]

While the genetics are not yet altered, nor is there gene splitting going on, the industry does want very specialized hybrids, both on the meat side and the hybrid egglayers. They are selectively bred to go, go, go and have excellent feed conversion. In most cases, these are 4 way crosses. Millions have been spent on research.

The industry has no interest in how long these specialized breeds live. The meat broilers are processed in just 8 or 9 weeks. On the layer side, It's pretty much "all in and all out" within two laying seasons. The birds are bred to mature early, lay heavy and no one cares should they suffer ascites, ovarian issues or burn out in 3 years. The layer industry doesn't keep them in the laying houses that long.

 

[Bullitt]

The discussion seems to be about very specialized hybrids that are probably obtained with multiple crosses. There may be some inbreeding going on also.

I have always heard that a hybrid from a single cross, such as a Red Sex Link from a Rhode Island Red or New Hampshire rooster and a Delaware hen, are generally more healthy than a pure breed.