Estimating genetic parameters of egg production in three local Tanzanian chicken ecotypes

Indigenous chickens (ICs) play a crucial role in ensuring food security, generating income, and supporting livelihoods in many developing countries. Despite their importance, ICs typically exhibit low productivity, particularly in egg production. Understanding their genetic potential is essential for developing sustainable breeding strategies. This study estimated genetic parameters for egg production and egg weight traits in three Tanzanian IC ecotypes: Ching'wekwe (n = 171), Kuchi (n = 220), and Morogoro Medium (n = 406). Birds from 13 hatches were raised under improved conditions, and egg production data were collected across six consecutive 90-day periods (EP1 to EP6), beginning at the age of first egg (AFE; mean = 164 ± 15.5 days). Laying status (LAY) was defined per period, with LAY = 1 if >3 eggs were laid and LAY = 0 otherwise. Additional egg production traits included average clutch length (ACL), number of eggs per clutch (EPC), and inter-clutch pause (ICP). The average annual egg production was 52.1 eggs per hen, and mean egg weight (EW) was 43.1 ± 5.5 g, peaking in EP5. Ecotype significantly affected most EW traits, with Kuchi hens laying the heaviest eggs and showing shorter clutch lengths and pauses (p < 0.05). Heritability estimates ranged from 0.1 to 0.6 for EP, from 0.1 to 0.4 for EW, from 0.1 to 0.2 for clutch traits, and from 0.1 to 0.3 for LAY. Genetic correlations between egg production in different periods were mainly positive (average: 0.38), and those among EW traits in various periods were strong and positive (average: 0.80). Clutch traits showed mixed or weak genetic correlations. Despite low productivity, the observed moderate heritabilities and positive genetic correlations between periods suggest scope for selection-based improvement. However, some unfavorable genetic correlations and age-related variability highlight the need for flexible, multi-trait selection strategies to balance production traits over time.