Poultry Brooding’s Next Shake Up: The Exploitation of Genomics
Here’s a fearless forecast on what’s brewing for poultry breeders and broiler raisers.
The poultry industry is now on the threshold of a new scientific expansion in genetic improvement through molecular breeding. Established breeding practices, inspired by quantitative genetics, treat the animal as a black box with an imprecise number of genes that dictate its varied characteristics.
The 1980s significantly mark this technological timeline, where, slowly but surely, this black box was opened. The first major development that changed the surface of poultry breeding was the discovery of genetic markers. Genetic markers that shape the most widely used category were small anonymous repeat sequences of DNA called micro satellites that are scattered across the entire genome and can be used as landmarks to create a map of the genome.
Fundamentally, these experiments calculated the co-inheritance of genetic markers that contained difference of traits of interest. Hence, scientists were able to localize the sources of significant amounts of genetic variability to a certain region of a chromosome, called a Quantitative Trait Locus. The first study of this type was done on Hybro birds and was reported by Van Kaam et al. (1998).
Previous mapping exercises in poultry breeding research have greatly improved by using markers and major genes, and may be much more accurately localized by a relatively minute set of markers. In fact, this may be mapped down to such narrow genomic areas that a few markers can be safely operated for additional selection for the major genes involved without the need to bring back the linkage phase on a regular basis.
More recently, a new whole genome marker approach is bit by bit becoming a practical choice. First proposed by Meuwissen et al. (2001), its rationale is that the genetic value of an individual animal can be acquired by assessing the effects of all genes or chromosomal positions at once. To achieve this, a required number of genetic markers should be met; that is of the order of magnitude of the number of genes and these would have to be assayed in all breeder candidates. The computational problems to carry out all the resulting data are not trivial, but the latest technical developments do bring Meuwissen’s visionary option within reach, making this a colossal effort.
G.A.A. Albers, A.P. Rattink and A.L.J. Vereijken of the Breeding Research Centre in Euribrid, Nutreco, Netherlands expect that over the near term, a growing number of major genes being directly selected for in poultry breeding programs worldwide will be seen. They also see aspects of genome-wide marker coverage applied for selected purposes. Taken together, they foresee that within ten years from now selection procedures based on genomic information will be a necessary part of every poultry breeding program.
Albers, Rattnik and Vereijken deem such assortment procedures could well turn into the core of the breeding program. After all, the genome is the central part of genetic variability, the livelihood of breeding companies.
A further speculation Would be that, if indeed the core of the selection program changes over time, the structure of the program, which is very much connected to the selection system, will also change. This will increase genetic progress. Maintenance costs of the program may also provide means of specifically directing the flow of genes to poultry production companies.
With that, molecular breeding techniques will sooner or later influence the functioning relationship between breeding companies and production companies. Thus, molecular breeding technology contains all aspects of what is called a breakthrough development.
The assembly of the chicken genome is indeed a major step towards the full elucidation of all gene structures of the chicken that has. so far, been made. The black box, on the other hand, will not be fully opened until the full trail is taken-from gene structure through gene function, gene expression, protein interactions, biochemical and signalling pathways, to cellular function and cell-cell communication towards a full awareness of how phenotypic performance of the chicken is regulated.
Although fully achieving it today is still impossible, through current and future research efforts in proteomics, metabolomics and all the other “-omics” areas, knowledge of this entire field will intensify exponentially as new technologies present themselves on hand. As a result, it is safe to predict that over the coming years many remote pathways from gene structure to phenotype will be understood. Once such knowledge is available, its exploitation through directed manipulation of gene structure and function is a natural next step.
For directed gene management to be feasible, there will also be a need for effective and efficient technology for genetic modification of birds. This has proven to be a major hurdle in avian systems and particularly the delivery of a transgene or gene construct to an avian embryo is much more complicated than in a mammalian system (Mozdziak and Petitte, 2004).
However, perseverance for more than 20 years in this area by several research groups (reviewed by Naito, 2003) has created definite progress and recently breakthrough-like successes have been claimed by at least two academic-private partnerships (Zhu et al., 2005, Viragen, 2006). Although current transgenics are focusing on applications in the pharmaceutical domain, these achievements do open the way to exploitation in poultry breeding for agricultural purposes.
However, this will take a lot of time. Firstly, much more knowledge on gene action in the chicken is needed to come up with a sound proposal for genetic modification of a chicken for agricultural use. Secondly, genetic modification systems for the chicken still need major improvements. After these two steps have been taken, the establishment of a genetically modified breed, from idea to introduction, takes at least another five years. Therefore, we expect the first genetically modified chicken with commercial potential in agricultural production to be on the market in 15 to 20 years from now.