Influencia da temperatura de incubação sobre o desenvolvimento ósseo de embriões e pintos de corte recém-eclodidos.

Abstract

Incubation temperature controls embryonic development and probably has an effect on skeletal formation and growth, which begins during embryogenesis. Thus, our aim with this work was to evaluate whether variations in eggshell temperature (above or below the recommended) during the middle stage of embryogenesis affect incubation yield, chick quality, utilization of minerals from the egg components and bone development of embryos and hatchlings. 2408 eggs from broiler breeders Cobb 500® with 45 weeks of age were incubated at four different eggshell temperatures (EST): 1) Control (EST of 37.8°C during the entire incubation period); 2) low EST (36.7°C between days 8 and 18.5 of incubation); 3) high EST (38.9°C between days 8 and 18.5 of incubation) and 4) very high EST (39.4°C between days 8 and 18.5 of incubation). Incubation yield (egg weight loss, mortality, fertility, hatchability, culling), chick quality (chicken body weight and length, yolk free body mass, residual yolk weight, relative organ weight, navel score), parameters of eggshell (weight, thickness, calcium, phosphorus, manganese and magnesium), yolk (Ca, P, Mn and Mg), blood (Ca, P, hormones T3, T4, PTH, calcitonin and vitamin D3, Alkaline Phosphatase) and bone (Ca, P, Mn, Mg, morphometry, ash, calcification and strength). The incubation temperature affected most of the analyzed variables. The incubation performance was worsened by all changes in EST, with very high EST being the one that most affected the evaluated indices, followed by low EST (p≤0.05). The organs relative weight was negatively influenced by the increase in temperature (p≤0.05). Low, high and very high EST promoted a reduction in chick quality; in the eggshell and yolk minerals utilization; in the blood and tibia minerals; worsening of bone characteristics and decrease in thyroid hormones, PTH and vitamin D 3 (p≤0.05). For all these variables, the very high EST caused the worst results. Calcitonin increased equally at high and very high EST (p≤0.05). Alkaline Phosphatase was increased by very high EST (p≤0.05). High temperatures markedly impaired the mobilization and utilization of minerals from egg components, calciotropic hormones and consequently, bone development during incubation. Eggshell temperature variations (above or below the recommended) during the middle stage of embryogenesis worsen incubation yield and chick quality.