Effects of genotype and season on the productive performance of commercial egg-type chickens in the derived savanna zone in Nigeria
Twelve (12) month production records of two commercial egg-type chickens, Nera Black (NB) and Isa Brown (IB) reared on a commercial farm in Ilora, Oyo State, Nigeria were analysed to assess effects of season and genotype on their performance. The production record was sorted according to the two recognized major seasons: wet (April-September) and dry (October-March) in the study area. Besides, the each major season was further partitioned into two sub-seasons namely: early rainy season (ERS: April-June), late rainy season (LRS: July-September), early dry season (EDS: October-December) and late dry season (LDS: January-March). Results of data analysis showed that genotype had no significant effect (P>0.05) on all the performance indices. Conversely, season significantly (P<0.05) affected all the performance parameters evaluated and hens performed better in wet seasons compared with dry months. There was significant (P<0.05) genotype by season interaction effect on egg production but not (P>0.05) for other productive parameters. IB strain performed better in wet season most especially in LRS while NB hens had better performance in dry season. Results from this study indicated that regardless of the season, the two egg strains should be employed for commercial egg production but adequate measure should be taken to combat the adverse effect of thermal stress on the welfare and performance of layers in the study area most especially in LDS months. Discrepancies in genotype by season interaction suggest genetic basis to differences in performances and physiological abilities of the investigated egg-strains to cope with stresses emanating from change in season.
Keywords: Egg-strains, genotype, productive performance, seasons.