Genetic response and metabolic adaptation to partial-record selection for egg production in Dokki-4 laying hens

This study aimed to evaluate the impact of partial-record egg production selection on egg production performance, serum biochemical constituents, and egg quality traits in Dokki-4 laying hens. A selection experiment was conducted over four generations involving 2,880 hens distributed across three experimental lines: high egg number line (SHEN₉₀), heavy egg weight line (SHEW₉₀), and a random-bred control line (RBCL). Selection criteria were based on performance during the first 90 days of production. Line effects were highly significant for all egg production traits, serum calcium concentrations, yolk cholesterol levels, and most egg quality traits. The SHEN₉₀ line showed superior egg number, annual egg mass production performance, and exhibited favorable metabolic profiles with reduced serum cholesterol and triglycerides. The SHEW₉₀ line achieved significantly heavier egg weights and improved shell quality traits compared to other lines. Genetic gain estimates revealed significant improvements in economically important traits. The SHEN₉₀ line showed favorable genetic gains for EN₉₀, EM₉₀, EM₃₆₅, and favorable reductions in serum cholesterol, triglycerides, and yolk cholesterol. The SHEW₉₀ line exhibited significant positive genetic gains in EW₉₀, EM₉₀, EM₃₆₅, and favorable yolk weight and yolk index percentages. Heritability estimates were moderate for selection criteria (EN₉₀: 0.22; EW₉₀: 0.17) and ranged from 0.09 to 0.31 for correlated traits. Genetic correlations revealed strong positive relationships between EN₉₀ and egg mass traits. EW₉₀ showed positive correlations with most external quality parameters. Selection for partial-record egg production represents an effective breeding strategy for simultaneously improving multiple economically important traits in Dokki-4 laying hens.