Location: Egg Safety & Quality ResearchTitle: Effect of genetic selection on growth parameters and tonic immobility in Leghorn pullets.) Author
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2011
Publication Date: 3/1/2012
Citation: Anderson, K.E., Jones, D.R. 2012. Effect of genetic selection on growth parameters and tonic immobility in Leghorn pullets. Poultry Science. 91:765-770. Interpretive Summary: Egg laying hens are continually bred to adjust for consumer and market needs. While the economic and egg quality alterations achieved through genetic selection are closely monitored, there is very little insight into “where we were” and “where we are now”. A study was undertaken to compare three closed genetic strains (no additional genetic changes made) and a modern strain of egg laying hens. Body weight, feed consumption, livability, and hen frame size have all been significantly affected by genetic selection. Hen fearfulness does not appear to have been altered. Therefore, the more modern laying hen is heavier and produces a greater number of eggs per pound of feed consumed without being more fearful
Technical Abstract: Four genetic strains of leghorn pullets were evaluated for effects of genetic selection on growth and fearfulness behavior. Three strains were closed, random bred stocks from 1950, 1960, and 1972. The fourth strain was a 1993 commercial laying stock. Pullets were reared in a brood/grow poultry house with flat deck cages. Each strain was comprised of 840 birds with 21 replicates per strain. Body weight and feed consumption were monitored bi-weekly. At 18 wk of age, a 20 hen sample from each strain was analyzed for body weight, body composition, and tonic immobility. There were significant (P < 0.05) differences among the strains for body weights of 1403, 1333, 1332, and 1428 g for the 1950, 1960, 1972 and1993 strains respectively. Furthermore, significant differences occurred in regard to feed consumption, livability, and frame size. There were no differences among the strains in tonic immobility. Genetic selection has affected growth parameters but there appears to be no change in fearfulness behavior.