Perfis térmicos na fase inicial de incubação sobre a embriogénese e desenvolvimento ósseo de pintos de corte

Abstract

The objective of this study was to evaluate how different thermal profiles applied gradually at the beginning of incubation influence embryogenesis, hatch performance, chick quality, nutrient utilization from egg components, biochemical profile, acid-base balance, hormonal response, and bone development in broiler chicks. 2.408 eggs from 45-week-old Cobb 500® breeder hens were incubated under four distinct eggshell temperature (EST) profiles, with gradual increase or decrease: 1) TC - control temperature (37.8°C throughout the incubation period); 2) TL - low temperature (36.7°C, from day 0 to day 8 of incubation); 3) TH - high temperature ( 38.9°C, from day 0 to day 8 of incubation); and 4) TVH - very high temperature (39.4°C, from day 0 to day 8 of incubation). Hatch performance (egg weight loss, fertility, hatchability, mortality, culling), chick quality (weight, length, yolk-free body mass, residual yolk weight, relative organ weight, navel score), hatch window, incubation duration, embryonic morphology, eggshell parameters (weight, thickness, Ca, P, Mn, and Mg), yolk parameters (Ca, P, Mn, and Mg), rectal temperature, blood assessments (Ca, P, GH, T3, T4, PTH, calcitonin, vitamin D3, alkaline phosphatase, glucose, uric acid, lactate, hepatic glycogen, and blood gas), and bone analyses (Ca, P, Mn, Mg, morphometry, biophysics, and mechanics) were evaluated. It was observed that the elevated temperature treatments (TH and TVH) accelerated embryonic development, resulting in a shorter incubation period. While the TL treatment, with a longer incubation period, indicated a more consistent and gradual development. The TL treatment positively influenced hatch performance, chick quality, bone and vital organ development, as well as the mobilization and utilization of minerals from the eggshell and yolk, along with the physiological and bone parameters of newly hatched chicks (p ≤ 0.05). It was concluded that the gradual increase in EST during the first week of incubation, as demonstrated by the TL treatment (36.7ºC), produced statistically similar or superior results to the control treatment in all analyzed variables. In contrast, elevated EST levels, especially TVH (39.4°C), are not recommended as they negatively affected the evaluated parameters.