The role of genetics in breeder selection

Frank Siewerdt, Cobb director of genetics


Breeding programs continue to achieve annual gains in broiler growth, feed conversion and breast meat yield. But this has been combined with steady improvements in bird health and welfare traits too, such as better leg strength and reduced mortality.
Despite this, some groups still believe the modern broiler has locomotion problems, even though this is not corroborated by feedback from company veterinarians and industry welfare officials.
This is because it is in the best interest of breeding companies to provide birds that thrive and stay healthy. Birds with good legs and excellent cardiovascular function are more efficient in field and have lower mortality rates.
Geneticists making selection decisions actively pursue those birds that are genetically superior for key traits that influence their welfare. They recognize that there is a strong synergy between welfare and bird performance; successful farms meet or exceed their production goals when the welfare needs of their flocks are met.

Breeding for health
Nature provides great variability among individuals of the same species. Within the same flock, there will be birds that differ in growth rate, meat yield, leg health and general immuno-competence.
The aim is to select elite birds with superior health indicators and the ability to excel in the commercially important traits. A typical elite breeder will have superior leg strength and a fully functional cardiovascular system, and will still be in the top percentiles for the key production traits.
Since at the time of selection none of these candidates will have reached sexual maturity, the decisions regarding reproductive ability are made based on information from close ancestors. Leg health is an essential component of reproductive performance, since both males and females need to be able to stand properly for matings to be successful.
All birds reaching market weight are thoroughly evaluated for structural leg defects. Family information is used to remove families that are more prone to traits such as tibial dyschondroplasia and femoral head necrosis.
The rest of multiple generations of selection consists of birds with the best genes are kept as pedigree breeders, so the frequency of these favorable genes increases in subsequent flocks. This simple mechanism can be quantified very precisely by population genetics theory and it enables the geneticist to improve flocks at a steady incremental rate year over year.

In the field
In addition to the welfare focus in the genetics program, Cobb is improving management techniques that will result in superior health and field performance. Combined improvements in genetics and husbandry have led to improved mobility, health and liveability of chickens at both broiler and breeder ages.
Defects, such as leg abnormalities, will continue to appear on birds because of natural variation and because growing conditions keep changing with time.
But the percentage of birds with health problems is much lower than in previous years.
New diet formulations, adjustments in environmental conditions and market preferences for different processing weights will continue to provide new challenges for geneticists, but the emphasis is to keep improving bird health and welfare.