December 12, 2016
When I first started my Light Sussex project (to pull them back from the brink of extinction as a livestock breed in Canada) I was deeply discouraged by the lack of vigour in the flocks I found, and I began to think that only some kind of magic could restore them. That made me curious about what genetic ‘magic’ commercial breeders had learned and applied to produce the new commercial broilers.
So, being a scientist, I went to the scientific literature, expecting to see the sequence of discoveries and applications explained and documented. But it isn’t there. And then I tried to order a text book on Poultry Breeding – there’s got to be at least one, right? Wrong.
What I discovered is that Poultry Breeding courses are not taught in North American universities any more, and in fact Poultry Science departments have been closed at almost every college and university on this continent. The most recent text book* was published in 1990 and has been out of print for more than 20 years. What happened?
It’s pretty simple. The multinational corporations that in the 1980’s and 1990’s were amalgamating all the primary producers of commercial chickens had come to regard the breeding methods as their own intellectual property. Rather than give grants to university labs to do the research (and have to publish the results), they started opening their own labs and doing it themselves behind closed doors.
I got a copy of that text book (from a rare book dealer, 5 months wait) and I read the chapter on commercial breeding which was amazingly vague. So I phoned the author who answered many questions and gave me some names of other retirees. Great guys, happy to talk about things that they had not been able to publish.
And now I can tell you, although in very simplistic terms, how they do what they do. But before I do I want you to understand what has happened to poultry breeding and to chickens in general in the last 100 years, because it has serious implications for heritage chickens and the survival of small farmers.
Since 1915 poultry breeding in Europe and the Americas has evolved from thousands of small independent farms hatching their own chicks with a little selective breeding, to 3 giant multinational companies that patent and control ‘their’ chicken genetics. The companies are:
Hendrix Genetics (Netherlands) – Layers: ISA, Babcock, Shaver, DeKalb, Bovan and HiSex. Broilers: Cobb-Vantress, Avian, and SASSO.
EW Group (Germany) – Layers: Lohmann, HyLine, H&N. Broilers: Ross, Arbour Acres, Indian River and Aviagen (which produces most of the grazer-type meat birds)
Grimaud Frères (France) – Broilers: Hubbard (incl. Freedom Rangers).
This means that any time you buy commercial chicks – including SASSOs, Freedom Rangers, Berg’s Grazers, etc. (but not Mistral Gris) – you are supporting these corporations. In Canada these corporations completely control the poultry industry and the poultry sectors of the CFIA and Ag Canada. I will let you contemplate the logical consequences.
Prior to the 1930’s chicken farmers and academic chicken breeders alike used ‘mass selection’ methods that I have described in the production breeding blog – essentially choosing the best male and female breeders from within a single flock by their utility performance, and generally staying within a single breed. If people crossed breeds it was to produce sex-linked chicks – a ‘terminal cross’ – or perhaps to develop a new breed. But the emphasis was on developing true breeding lines that were superior for some trait. Genetically this is a self-limiting endeavor.
Commercial breeding techniques arose from copying methods used by plant crop breeders. Hybrid corn and sorgum cultivars were amazingly productive compared to purebred cultivars, and plant breeders had rapidly progressed from 2 way crosses to 3 and 4 way crosses to increase ‘hybrid vigour’ even more. Hybrid vigour is created when the 2 parents are genetically dissimilar, so it is what you get when you cross 2 unrelated breeds or lines. A 4 way cross starts with 2 maternal grandparent lines producing a mother line, and 2 paternal grandparent lines producing a father line, and the next generation crosses the mother line with the father line to get the ‘product’ line.
Breeding companies rushed to try as many different lines as possible in order to find the best crosses, and the birds produced by these crosses were significantly superior to anything that pure bred breeding could produce. The 1950’s saw a big increase in consumption of eggs and chicken that were more efficiently produced than previously.
This era launched most of the companies that now dominate chicken genetics. But it also put thousands of smaller breeders out of business.
Obviously you need a lot of poultry barns and employees to keep the 4 grandparent lines – at least 2 flocks for each line, as insurance, because if an accident or disease wipes out a flock you can’t get replacements from anyone else! And then add the 2 parent flocks… this has come a long way from Farmer Brown keeping his single flock of Barred Rocks. So 4 way crossing never caught on with non-commercial breeders.
The next step was a shift from selecting breeder hens and roosters on their own merits to selecting them on the traits of their offspring – progeny selection. Using progeny selection for every generation is called Recurrent Selection. In order to do this, you have to ‘progeny test’ your candidate breeders: Each rooster is mated to a small group of hens from the Mother flock, and the offspring are grown and evaluated for the trait of interest (or several traits). This is like choosing new dairy bulls based on their daughters’ milk production. It allows you to breed for traits other than the most obvious ones, such as fertility in a broiler breeding program, or feed conversion in a layer program. Progress with recurrent selection is slow but steady if the best genes are x`available in the flocks.
Enhancing the progress can be done by Reciprocal Selection. The concept came from studies of the genetics of coevolution – i.e. the parallel development of two different species that have frequent interactions with each other. This is seen in the study of domesticated animals, in which the animal becomes better and better suited to the uses of man while the humans become better adapted to the products of the animal, e.g. the enhanced dairy traits of cattle parallelling the increased frequency of adults capable of secreting lactase.
In the case of chicken breeding, which is in too much of a hurry to advance at an evolutionary pace, additional genetic variation is added to one or more of the grandparent lines (by outcrossing) to see if better genetic combinations will result. The two techniques are commonly used simultaneously, and called Recurrent Reciprocal Selection (RRS).
If RRS has your head spinning, you are probably not going to like the next and final phase of commercial chicken breeding. I will be brief.
The mapping of the chicken genome and the ability to identify regions on chromosomes that correspond to identifiable traits has given geneticists the key to the toolbox of breeding. Why look at the animal if you can look directly at his genome, eh? Well, at least your computer can ‘look’ directly at his genome.
Molecular Selection uses QTL (qualitative trait locus) mapping and marker assisted selection to make sure that those hybrid vigour producing crosses are loaded with the best combinations. And they find more every year. Molecular Selection has many applications outside of chicken breeding, but when it is used in chicken breeding it makes RRS into MRRS. Just so you know.
Note: this is not genetic engineering (GE). No DNA is being added from a different species. These techniques only use DNA that is naturally occurring in chickens. They just use it with an extraordinary degree of precision!
If this information has inspired you to decide to become a commercial chicken breeder, don’t try to enroll in a university program – there aren’t any anymore.
*Crawford, R.D. Editor. Poultry Breeding and Genetics. 1990 Elsevier, Amsterdam.