Professor Paul B. Siegel of Virginia Tech reviewed genetic progress over the past few decades with emphasis on the response of flocks to nutrition during his address, “Feed Efficiency from a Breeding and Genetic Viewpoint,” at the Midwest Poultry Federation Convention.
Professor Paul B. Siegel
Consolidation among primary breeders has reduced the number of strains available to producers. At the same time recent acquisitions may have benefits through concentrating resources on selection for traits of commercial significance. Geneticists affiliated with the remaining major multi-national breeders are required to balance reproductive efficiency, livability and product quality to suit a broad spectrum of climatic and housing conditions and nutrient profiles based on the availability and type of ingredients.
Economics affect selection
Dr. Siegel stressed that geneticists should focus selection programs on the needs of consumers and the markets they represent. Apart from the fact that demands are constantly changing, feed costs and micro-economic factors influence the economics of poultry production.
Despite the current emphasis on molecular genetics, poultry breeding will depend strongly on quantitative genetics since genotypes cannot be separated physically from the environment. Dr Siegel stressed the fact that significant traits related to production are multifactorial and that genetics in fact represents only 30% of heritability of some commercial parameters. He acknowledges that molecular genetics can be used to identify lines with beneficial traits but does not envisage either transgenesis or cloning for commercial production.
Controlling feed intake
A significant future challenge will be to understand the regulation of feed intake including the neural systems which control satiety and hunger. To illustrate the complexity of the issue Dr. Siegel described an experiment in which broilers selected for a range of growth rates and feed efficiency were compared. Three lines known to differ in growth potential were fed either a single balanced diet or allowed free choice between two diets which differed in protein and energy content but which when combined in equal proportions corresponded to the nutrient content of the balanced diet.
Broilers fed a balanced diet achieved the heaviest weight with the most beneficial feed conversion efficiency, highest breast meat yield and lowest fat content than broilers allowed free choice. High growth weight was however associated with elevated mortality. Broilers allowed free choice selected diets which predicated survival at the expense of growth and hence would deprive producers of optimal economic benefit.
It is anticipated that cumulative improvement in performance will continue over succeeding generations applying quantitative genetics. Optimal nutrition, control of disease and stockmanship are however required to achieve genetic potential.