Abstract
Major marker genes are believed to confer not only adaptability to the tropical climate, but also resistance to diseases. During the last two decades, many investigations have observed that naked neck and frizzle genes have favourable effects on immunocompetence in chickens raised under high ambient temperatures. As a result, several tropical countries have introduced these genes in breeding programs to improve both the productive performance and survival rate of chickens.
Acknowledgements
This paper would not have been possible without all faculty staff of poultry breeding and genetics at Ain Shams University, Cairo, Egypt. The authors are grateful to farm workers for their effort, patience and love during the long time of extensive experimental work.