Thiruvenkadan, 2010 – Layer breeding strategies: an overview

Layer breeding companies apply selection criteria to improve over 30 traits important for commercial egg production. Intensive selection for egg production over the decades has resulted in a significant reduction in genetic and phenotypic variations in egg production, however the decrease in genetic variation observed in commercial lines are not yet critical. Peak production now approaches the biological limit of one egg a day, but in early production (at sexual maturity) and late production (persistency) genetic variation is still high. Including these traits in the selection criteria will improve the egg production in commercial birds. Due to high heritability and the absence of any significant negative effects on production parameters, residual feed consumption is used as selection criteria to improve the feed efficiency. Considerable research has been carried out on egg weight, eggshell strength and internal quality of the eggs and improvements have been made as a result of selection. With the reintroduction of floor system and increased consumer interest in processed eggs, in future more emphases have to be given to the eggshell strength and internal quality of the eggs. Poultry production in the unfavourable environmental conditions of the tropics is hindered by direct and indirect heat stress leading to a general depression in performance. Results on the utilisation of naked-neck and frizzle gene in high-ambient temperatures is encouraging, and, in future, will play an important role in production of layer lines suitable for overcoming such genotype-environment interaction. Feather pecking is an undesirable behaviour, which causes major problems in non-cage systems. Several authors have identified a hereditary basis of feather pecking behaviour, which is suggested by strain differences. Hence, selection of birds with no or very low tendency to perform feather pecking should reduce the incidence. Recent molecular genetic studies resulted in identification of QTL affecting different economic traits and identification of candidate genes causing variation in performance among birds. In future these findings will play a major role in further genetic improvement of layers without any negative effect.