Correlated responses to selection for increased intramuscular fat in a Chinese quality chicken line

The correlated response in traits encompassing meat quality, carcass, sexual maturity, egg production, and egg quality traits arising from selection for increased intramuscular fat (IMF) content of breast muscle were investigated in the fifth generation of a selection experiment including a line (F) selected for increased IMF and a randombred control line (C). The results showed that breast muscle IMF content in the F line (4.25%) was significantly higher (P < 0.001) than that in the C line (3.80%) after 5 generations of selection. The same trend was observed in IMF content in thigh muscle (20.03 vs. 19.41%, P < 0.05). The shear force of breast muscle in the F line was lower than that in the C line (1.82 vs. 2.12 kg, P < 0.01), whereas increases occurred in BW (P < 0.05), carcass weight (P < 0.05), breast muscle weight (P < 0.001), breast muscle percentage of live weight (P < 0.05), abdominal fat weight (P < 0.001), ovarian weight at 90 d of age (P < 0.05), and egg weight (P < 0.05) in the F line, relative to the C line. Age at first lay in the F line was 4.84 d earlier than that in the C line (P < 0.001). No differences were found between the 2 lines (P > 0.05) in the following traits: drip loss, meat color (L*, a*, and b*), carcass percentage, thigh muscle weight, thigh muscle percentage, abdominal fat percentage, first egg weight, egg number (until 43 wk), Haugh units, shell thickness, and egg shape. The results of the present study demonstrated that selection for breast muscle IMF leads to desirable changes in meat quality, carcass, sexual maturity, and egg production traits.