Impact of hen treatment with bee pollen and thermal manipulation during early egg incubation period on the hatchability and embryonic development of chicks

The aim of the experiment was to evaluate the effect of different incubation temperatures on hatchability, embryonic development and physiological responses of chicks produced from hens treated with bee pollen (BP). In total, 600 Sinai hatching eggs were equally collected from hens treated with 0, 500, 1000 and 1500 mg BP/kg diet (four dietary groups) and then divided into two equal incubation groups. In the group 1, eggs were incubated at normal temperature (37.5 °C) up to the day 18, while those in the group 2 were incubated at the same conditions except 3 days (days 6, 7 and 8) during which eggs were exposed to chronic temperature (40 °C) for 3 h a day. The highest relative water loss (RWL) and embryonic mortality (EM) were observed in the chronic group (P ≤ 0.05) as compared with control. The hatchability percentages for set (HSE) and fertile eggs (HFE) in the chronic group were significantly (P ≤ 0.05) decreased, while dead after piping (DAP) was insignificantly increased in comparison with control. Blood heterophils : lymphocytes (H : L) ratio, and triiodothyronine (T3) and thyroxin (T4) levels were significantly (P ≤ 0.05) influenced by incubation temperatures. Egg weight (EW8d) (at dose 1000 mg BP/kg), HSE, HFE for eggs produced from hens treated with BP were significantly (P ≤ 0.05) higher, while the percentages of DAP (for doses 500 and 1000 mg BP/kg) and EM were significantly (P ≤ 0.05) lower in comparison with control. T3 plasma content (for doses 500 and 1000 mg BP/kg) for chicks from BP-treated hens was significantly (P ≤ 0.05) higher, while H : L ratio (for doses 500 and 1000 mg BP/kg) was significantly (P ≤ 0.05) lower as compared with control. The obtained results showed that eggs exposure to higher temperature in early incubation period negatively influenced hatchability, and chick quality traits and haematological parameters; however the addition of BP into hen diet can improve the examined parameters and so reduce the adverse effects of high incubation temperature.