A BSTRACT

A total of 135 and I 79 day-old chicks were generated in two planned breeding experiments to evaluate (he effect of main and reciprocal crossbreeding on growth, egg production and egg quality characteristics of normal feathered (NF), naked neck (Na) and frizzle (F) chickens crossed with Arbor Acre broiler breeder stock (F) in a humid tropical environment. Six genetic groups consisting of three main and three reciprocal crosses of F1and F2hackcrosses were generated in experiments I and II, respectively. The F1 hybrids; FxNF, FxNa, ExF and NFxE, NaxE, FxE and thcF2 backcross prugellies; Ex(EXNI'), Ex(txNa). Ex([xF) and Ex(NFxE), Ex'(Naxl.). Ex(FxE) were utilized in the study. Experimental design in both experiments was a randomised complete block (RCD) with genetic group as a major factor of interest and hatches as block. Result of growth studies revealed that the main COSS I'I hybrid chicks are significant less (I'rn-0.05) in day-old body weights when compared to their reciprocal crossbreed counterparts. These difference in body weight persisted through the growth and subsequent laying periods. Average daily lëed intake (ADFI) was higher in the reciprocal F, crosses with better feed conversion ratios (FCRs). l3rooding and rearing mortality rates were highest in the naked neck genotype in both main and reciprocal F, crossbreds. There was evidence of sexual dimorphism between male and finale birds in each of (he genetic groups with the cockerels weighing more than the pullets in body weight and most of the linear body measurements (Ii Ms). The l'riiile birds (cockerels and pulle(s) attained signi licaiitly (P<0.05) highest body weight in the reciprocal F, crossbred at 18 weeks, II1owcd by the normal feathered birds and then naked neck individuals. Egg production traits namely; body weight at first egg (BWFE), age at first egg (AFE), weight of first egg (WFE) and short terrn-90 days eg number (ENq ) were significantly (P<O.05) better in the reciprocal F, crosses with the naked neck individuals in this crossbred group having the highest WFE and FN 1. The egg quality (rails namely; egg weight (EWT), shell thickness (ST), albumen weight' (AWT), yolk index (YIND) and Haughty unit (liii) were significantly (P<0.05) higher in the reciprocal F, crosses except yolk weight (YW1), which showed no significant differences in both crosses. Correlation between I3WFE and AFE were low or negative showing that age at sextile maturity had little or no relationship to adult body size. vl, ile correlation between UWEI and egg weight (EWT) were positive in most of the genetic groups except in the naked individuals. also correlation between 13W1F, and I ,N, was low or negative in lilost genetic groups except in IxNF genetic group where correlation (r 0.89) was high and positive. In experiment II, the reclpn)cal I ) backcrosses jl x(NFxl ), I x(Naxl) and Ex(FxE)J hid superior body weights from day-old, better FCRs and greater linear body structure developments compared to their main cross F2-backcross counterparts. These reciprocal F2backcross individuals also had significantly (P<O.05) better RWFF. lN(. WFI and better egg quality traits. There was clear evidence of maternal effects in, the expression of growth and egg traits in both experiments with each genetic. going math feeling more of the characters of its dam-of--origin. Generally. reciprocal crossbreeding resulted in offspring with improved growth, egg production and egg quality traits. It was therefore, concluded that for rapid improvement of these traits in crossbred chickens crossbreeding option should he adopted; that the frizzle gene was relevant in 2nh1Incing growth and egg production potentials of crossbred chickens in the humid tropics while the naked neck gene could be useful in egg weight arid egg number improvement in the chicken, with reduced livability problems.