GROWTH PERFORMANCE, CARCASS COMPOSITION AND TENDERNESS OF MEAT IN MALE LAYER-TYPE CHICKENS SLAUGHTERED AT DIFFERENT AGE

An experiment with male layer-type chickens was carried out in the In-stitute of Animal Science-Kostinbrod, aiming to investigate their growth per-formance and carcass composition, as well as the cooking loss and tenderness of the meat at the age of 5 and 9 weeks. The birds were reared in controlled microclimate, with initial stocking density of 22 birds/m2. After 5 weeks of age, fragmentation of the stocking density was applied and it was diminished to 7 birds/m2. Chickens were slaughtered at 5 and 9 weeks of age, and 10 chickens of each age group were subjected to carcass analysis. The average live weight of the birds at 5 weeks was 329 g, while the 9 weeks old chickens reached 1096 g. In order to attain the weight of the first age of slaughter (5 weeks) the chickens gained 294.03 g with a feed conversion ratio of 2.97, whereas for the whole period the feed conversion ratio was 2.91. The dressing percentage of the 5 weeks old chicks was 51.26%. For the 9 weeks old it was 77.62%. The age affected the yield of the main carcass components and the older birds had higher yield of breast (P = 0.0035) and thighs (P < 0.0001). The cooking loss for both breast and thigh meat was higher in younger chickens (P < 0.0001). The tenderness measured as Warner-Bratzler shear force (WBSF) of breast and thigh remained unaffected by the age at slaughter. Its values classified the meat of the male layer-type chickens from this trial as "very tender".