Effects of eggshell temperature pattern during incubation on tibia characteristics of broiler chickens at slaughter age

Abstract This study was designed to determine effects of eggshell temperature (EST) pattern in wk 2 and wk 3 of incubation on tibia development of broiler chickens at slaughter age. A total of 468 Ross 308 eggs were incubated at an EST of 37.8oC from incubation day (E) 0 to E7. Thereafter, a 2 x 2 factorial arrangement with 2 EST (37.8 and 38.9oC) from E8 to E14 and 2 EST (36.7 and 37.8oC) from E15 till hatch was applied. After hatching, chickens were reared until slaughter age with the four EST treatments and 8 replicates per treatment. At d 41 and 42, one male chicken per replicate per day was selected and hock burn and food pad dermatitis were scored. Rotated tibia, tibia dyschondroplasia, epiphyseal plate abnormalities, bacterial chondronecrosis with osteomyelitis, and epiphysiolysis were assessed. Tibia weight, length, thickness, head thickness, and robusticity index were determined. X-ray analyses (osseous volume, pore volume, total volume, volume fraction, mineral content, and mineral density), and a 3-point bending test (ultimate strength, yield strength, stiffness, energy to fracture, and elastic modulus) were performed. A high EST (38.9oC) in wk 2 of incubation, followed by a normal EST (37.8oC) in wk 3 resulted in higher mineral content (P=0.001), mineral density (P=0.002), ultimate strength (P=0.04), yield strength (P=0.03), and stiffness (P=0.05) compared to the other 3 EST groups (wk 2 x wk 3 interaction). A high EST (38.9oC) in wk 2 of incubation, regardless of the EST in wk 3, resulted in a higher tibia weight (P