Shambel Taye - Ethiopian Institute of Agricultural Research, Debre Zeit Agricultural Research Center, P.O. Box: ۳۲, Bishoftu, Ethiopia
Gebeyehu Goshu - Addis Ababa University, College of Veterinary Medicine and Agriculture, P.O. Box: Bishoftu, Ethiopia
Solomon Abegaz - Ethiopian Institute of Agricultural Research, Debre Zeit Agricultural Research Center, P.O. Box: ۳۲, Bishoftu, Ethiopia

The study was designed to evaluate the growth performance of exotic dual-purpose chicken breed of Koekoek (K) and Kuroiler (Ku) crosses with an improved Horro (H) chicken under reciprocal mating to select potential crosses for development of a synthetic breed in Ethiopia. The experiment was carried out on seven genotypes, including three pure lines (i.e., Horro, Koekoek, Kuroiler) and their direct (K × H, Ku × H) and reciprocal crosses (H × K and H × Ku). A total of ۴۴۶one-day-old chicks from the seven genotypes were randomly distributed between pens using a completely randomized design with three replications (experiment period?). Data on body weight at hatch (DO), ۴, ۸, ۱۲, ۱۶ and ۲۰ weeks of age, body weight gain, feed conversion rate (FCR) and mortality rate were calculated during the experiment. The crossbreeding effects were estimated to select the best genotype as a dam or a sire line in the synthetic breed for the next generation. The result showed that the highest mean body weight (P < ۰.۰۵) and body weight gain were related to Horro×Kuroiler crossbred chicken that followed by Ku×H, and pure Ku at most of studied ages. Average feed intake was comparable among genotypes. Additive (Ae), maternal and heterosis effects for body weight were significantly (P < ۰.۰۵) positive at most ages for both crosses. Additive effects range from ۱.۷۹ to ۱۰.۱% for Horro-Koekoek crosses, whereas it ranges from ۱.۶ to ۴۴% for Horro-Kuroiler crosses. In Horro-Koekoek crosses, the highest positive contribution of maternal effect was observed for body weight at eight weeks (۸.۲۲ %). Estimates of heterosis effects (He) were positive and ranged from ۶.۵۴ to ۱۳.۷۹%. In the Horro-Kuroiler crosses, estimates of maternal additive (Me) and the heterosis effects on body weight were positive and significant (P < ۰.۰۵) at ۸- and ۱۲-weeks of age. Generally, the positive and significant additive effects suggest merits of the sire line in the growth performance which favors use of Kuroiler and Koekoek as sire lines to improve the body. Positive values and significant contribution of heterosis indicate the substantial effect of crossbreeding on body weight at most of the studied ages. From this study it can be recommended that crossbred hens sired by improved Horro (H × Ku) can be used for growth performance potential in the forthcoming synthetic breed development program.

Chicken, Body weight, Crossbreeding, Additive effects, Heterosis effects