Effect of long-term selection for juvenile growth on bilateral asymmetry in broiler chickens

The present investigations were conducted on 3619 birds of PB-2 strain and 200 birds of control line to study the growth and bilateral asymmetries for shank width (SW), anterior posterior length (APL) and shank length (SL) and their inheritances. Body weight and trait sizes for SW, APL and SL were significantly higher in PB-2 than control line at 3 and 5 weeks. The percentage increase in body weight and trait sizes for SL and SW were higher in control line and reverse was true for APL. Fluctuating asymmetries (FAs) and relative asymmetries (RAs) for APL and SL at 3 weeks and for APL, SL and SW at 5 weeks were significantly higher in PB-2 strain. The h² of various bilateral asymmetries at 3 and 5 weeks in males and females were found to be low (0.00–0.11). The genetic correlations of body weight with trait sizes of bilateral traits ranged between 0.393 and 0.954 at 3 and 5 weeks while the phenotypic correlations varied between 0.457 and 0.619 and were generally lower than genetic correlations. FA, RA for SW, DAs for APL and SW at 3 weeks had negative genetic correlations with body weight. FAs and RAs for SL and SW at 5 weeks had negative phenotypic correlations (−0.273 to -0.331) with body weight. At 5 weeks of age FAs for APL and SL, RAs for SL and SW and DAs of APL and SW had negative genetic associations with body weight.