1215
Crossbreeding effects for body weight and carcass characteristics in a 3-breed diallel cross
A 3 x 3 complete diallel mating system involving three chicken breeds namely Potchefstroom Koekoek (P), Venda (V) and Ovambo (O) was used to estimate crossbreeding genetic effects (heterosis, maternal effects and combining abilities) for growth and carcass characteristics. Nine genetic groups consisting of 25 chickens per group were produced which were reared from hatch to 10 weeks of age. Body weights were recorded at hatch, 4, 8 and 10 weeks of age while meat quality analysis (colour, pH and tenderness) of the breast meat was done at slaughter age (10 weeks). Meat tenderness was determined using the Instron-Warner-Bratzler Shear Force (WBSF). Potchefstroom Koekoek (P) was heavier at all different growth stages amongst the purebreds while the Venda had the lowest weights at all different growth stages. The highest level of heterosis (30% and 21%) was observed in the V X P cross at 8 and 10 weeks respectively. The P x V cross showed positive estimates of maternal effects except at 10 weeks of age. High and positive general combining ability (GCA) was observed in the Potchefstroom Koekoek (P) breed. The P x V showed positive effects of specific combining ability (SCA) at hatch, 4, 8 and 10 weeks of age. With respect to meat characteristics, the Pochefstroom Koekoek breed had higher values of a* (redness) and b* (yellowness) colour indicators in comparison to the other chicken breeds. Potchefstroom Koekoek and P x O breed had higher values of pH at 2 hours and 24 hours after slaughter. The pH declined in all the nine genetic groups at 2 hours to 24 hours except for the P x O which increased. The O x P had the highest shear value (74.80) while the lowest shear force (43.62) was observed in the P X V genotype. The P X V and its reciprocal cross, V X P could be further evaluated for other characteristics such as egg production and used as base for improved indigenous chicken production. It may be worthwhile to also consider developing a composite chicken breed based on these two breeds.
Keywords: crossbreeding; heterosis;