The effect of breeder age on long bone development was studied in chicken embryos from 12 days of incubation until hatching. Fertile eggs were incubated and randomly assigned in a 2 x 6 factorial arrangement (two breeder ages -38 and 60 weeks and six incubation days -12, 14, 16, 18, 20, and 21). Enzymatic activity of acid and alkaline phosphatases in tibial epiphyses and weights as well as length and width in tibias and femurs of the embryos were determined. Tartrate-resistant acid and alkaline phosphatases activity in epiphyses was not affected by breeder age. Absolute weight and width of femur and tibia were larger in 60-week-old embryos compared to 38-week-old. Enzymatic activity and morphometric measurements increased with incubation day, independently of breeder age. The results showed that the process of endochondral ossification during the last two thirds of embryo development was not influenced by the age of the breeders. Although, in terms of absolute weight, the long bones of embryos from older breeders were heavier, which was associated with the larger width of the bones, but and not with their length.Keywords: chicken embryo, alkaline phosphatase, epiphyses, growth plate, long bones de incubação -12, 14, 16, 18, 20 e 21 dias RESUMO O efeito da idade da matriz sobre o desenvolvimento dos ossos longos foi estudado em embriões de frango de 12 dias de incubação até o nascimento. Ovos férteis foram incubados e distribuídos em delineamento inteiramente casualizado em arranjo fatorial 2 x 6 (duas idades de matriz -38 e 60 semanas e seis dias

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