Asymmetry measures and allometric growth parameter estimates for investigate effect of early feed restriction on deviation from bilateral symmetry in broiler chickens

Abstract. The purpose of this study is to investigate the effect of different feeding programs such as ad libitum feeding (AD), 20 % feed restriction based on ad libitum group (FR1) and not fed between 9 a.m. and 3 p.m. (FR2) on deviation from bilateral symmetry or developmental stability in broiler chickens by means of two different approaches namely asymmetry measures and allometric growth model parameters. The weekly left and right sides of shank length, shank width, wing length and face width of chickens were collected from 7 days of age to 42 days of age. Results of this study showed that the deviations from the bilateral symmetry were mostly in fluctuating asymmetry (FA) in the FR1 group birds. On the other hand, the deviations from the bilateral symmetry in the birds in group AD and FR2 were mostly in the form of anti-symmetry (AS) and directional asymmetry (DA) respectively. In this study, the deviation from the bilateral symmetry was mostly in FA type for the measured morphological characters for the FR1 group, and the FA level was usually lower indicating higher welfare level and lower developmental instability for these animals than that of the AD and FR2 groups. Allometric growth coefficients for evaluating the effects of the feeding programs on the developmental stability were a little bit different from the findings obtained by the asymmetry measures‘ being taken into account. Allometric growth parameters, therefore, should be taken into consideration, along with asymmetry measures when investigating effect of rearing conditions or environmental conditions on developmental stability. As a conclusion, intensive feeding (AD) and long-term feed restriction (FR2) can be said as an important environmental factor affecting developmental stability and dependently the animal welfare and performance.