Paper Title
Effect of Crossing Between Local Chicken with Isa Brown on Growth Performance in Iraqi Kurdistan Region

Abstract
This study conducted at College of Agriculture in collaboration with Animal Production Department; Directorate of Agricultural Research�Erbil during the period from Sept. 2013 to the end of May 2014. Four hundred and twenty one chicks belong to three local genetic groups and their crosses with Isa Brown were resulted from hatching. They kept in replicates and their body weights recorded at 1-day of their age and weekly then the accumulative body weight, body weight gain, feed consumed and feed conversion ratio were calculated at the end of first (from1 day to 4 weeks) and second (from 5 to 9 weeks) of age. General Linear Model within the SAS program was used to analyze the collected data to study the effect of genetic group on the studied traits. Duncan Multiple Range Test was conducted to diagnosing the differences between the means of the levels of each factor. Heterosis percentages were calculated. The overall mean of chick's body weights at 1-day of age, 1st and 2nd ages were 38.48, 210.47 and 743.68 g, and body weight gain for the 1st and 2nd ages were 171.98 and 533.21 g, respectively. Genetic group was found to have a highly significant effect (P≤0.01) on body weights of chicks as well on body weight gains. Overall mean of feed consumed per bird at the 1st and 2nd ages were 610.20 and 1852.99 g, respectively. Although there were no significant effects of genetic group on feed consumption/bird at both ages, it showed that there were significant differences (P≤0.05) between them at the 1st age only. Feed conversion ratio of chicks belongs to different genetic groups at the 1st and 2nd ages averaged 3.513 and 3.505 kg/kg, respectively, and their effect by genetic group was not significant. However, the differences between the means of genetic groups were significant (P≤0.05) at the 2nd age using Duncan test. The higher percentage of heterosis (15.732) was recorded for the cross (L2 x L5) at 1-day old, while the lower percentage (-12.927) was recorded for the cross (L5 x L2) at the same age. It could be concluded that: The chicks resulted from local lines grow slower than those resulted from the mating between their males with Isa brown females. There were differences in the percentages of heterosis calculated for body weights of chicks resulted from local males and Isa brown females and their reciprocal. Keywords� Local chicks, Heterosis, Growth Performance.