Genotype by Environmental Interaction Effects on Laying Characteristics of Lohman Brown in Sub-Humid Tropics of Nigeria

Egg production performance of Lohman breed were collected from production record at the Livestock Teaching and Research Farm Federal University of Agriculture Makurdi, Nigeria. The records were collected from 2010 – 2015 to assess the effect of year and season on brooding mortality, age at first egg, at peak production, hen-day lay at 25 weeks and at peak production when the data were subjected to descriptive statistics. There was significant (p < 0.05) difference in brooding mortality between seasons and years. The study also showed that age at first egg varied significantly (p < 0.05) between the years. The age at first egg of 2010 and 2011 were similar but both differed significantly (p<0.05) from the age at first egg of the year 2014. Age at peak production were also significant at (p < 0.05) between the years. There was delayed age at peak production in 2010 and 2011 while that of 2014 came earlier. There were also significant differences (p < 0.05) in peak hen-day lay between the years. There were also significant differences (p < 0.05) in hen-day lay at 25 weeks between the years. The hen day-lay of 2014 had the least value. This implied that there was variation in the climatic conditions across the years and seasons that affected these parameters in varied degrees, that also elicited varied deviation and responses from the genotype. The dry seasons enhanced higher deviation and reduced response on these performance from the genotype, while the deviation from the effect of the wet seasons were less with higher responses from the genotype on these performance. This indicated that climatic conditions and their effects varied between and within years. Brooding mortality, age at first egg and at peak production were the parameters that were highly affected. A good stocking plan to enhance brooding, age at first egg and at peak production to occur in the wet season will enhance higher responses, reduce deviation from climatic impact and increase egg production performance.

Keywords: Age-at-peak, climatic- condition, genotype, hen-day- lay, peak-production, year.