Evaluation of effects of a strain, stocking density and age on bilateral symmetry of broiler chickens

Abstract

The study was conducted to assess bilateral symmetry of broiler chicken strains raised on different stocking densities. The study lasted for eight weeks with 216 broiler chickens belonging to three different strains used for the experiment: Marshal, Ross 308 and Arbor Acres. The birds were randomly allotted to three different stocking densities of 10, 12 and 14 birds.m-2, respectively. Each treatment was replicated twice in a 2 × 3 factorial design. Left and right leg length, wing length and face length of the same birds from each group were measured weekly from 35th to 56th days of age using a digital caliper. The morphological data collected on the birds were used to estimate bilateral symmetries. Data were subjected to analysis of variance (ANOVA) using a Statistical Analysis System, SAS (2004). The results showed that effect of strains on bilateral symmetry of face length of the broiler chickens was not significant (p > 0.05). The bilateral symmetry of the wing length was significantly affected by a strain of the broiler chickens. The results showed that effect of stocking density on bilateral symmetry of face length of the broiler chicken was not significant. The bilateral symmetry of wing length was significantly affected by the stocking density of the chicken. There was a significant effect of age on bilateral symmetry of face length of the chicken. There were significant interaction effects of strain and stocking density on bilateral symmetry of broiler chickens. Based on results of the study it is concluded that the bilateral symmetry of morphological traits, as estimated by directional asymmetry, fluctuating asymmetry and relative asymmetry, were affected by a strain of the chicken and stocking density. Thus, the strain and stocking density may be claimed as important factors affecting developmental stability of broiler chickens.