Heterosis effect in hybrid laying hens

The new original egg laying lines T, P and N selected at the Institute of Agriculture - Stara Zagora were used. Hybrid Т♂ × Р♀, Р♂ × Т♀ crosses were obtained and used for paternal line. Thereafter, the following breeding schedule of paternal and maternal lines was applied: Group I - (Р♂×Т♀)♂ ×N♀; group ІІ - (Т♂×Р♀)♂ ×N♀; group ІІІ - Т♂×N♀; and group ІV - Р♂×N♀. The production traits of original and hybrid birds were recorded: live weight at the age of 8 and 18 weeks, age of sexual maturity in days, 150 days egg production, average egg weight - at 2-week intervals until end of lay; livability, heterosis effect. The live weights of hybrids at 8 and 18 weeks of age were statistically significantly lower compared to original lines. The values of heterosis for this parameter were negative for all four hybrid combinations. The earliest beginning of egg lay occurred in (T♂×Р♀) ♂ ×N♀ (162.08 days of age) and Р♂×N♀ (163.11 days of age). The relative (%) heterosis for age of sexual maturity of studied hybrid combinations had moderate to low negative values. Average egg weights of hybrids were higher and the values of heterosis - positive for all four groups varying from 0.97% to 1.63%. The average 150 days egg production was lower in purebred lines compared to hybrids. The highest average 150 days egg production was determined in P♂×N♀ hybrids - 142 eggs. The heterosis effect for egg production in hybrids was significant.