ABSTRACT:The objective of this study was to investigate the impact of spraying ascorbic acid on Japanese quail eggs submitted to high temperature during4th to 14th days of incubation period on embryogenesis, hatchability, embryonic mortality rate and chick quality.Six hundred Japanese quaileggs were divided into two equal groups of 300 eggs each according to incubation temperature. In the first group: eggs were incubated at 37.5°C (thermoneutral incubation temperature NIT 37.5°C)and 65% relative humidity (RH)from 1st to 14th days of incubation. The second group: (high incubation temperatureHIT 41°C): Eggs were incubated at 37.5°C during the first 3 days of incubation and from day 4th to 14th incubation temperature (IT) was raised to 41°C and RH65% for three hours per day. The eggs were evenly divided into three ascorbic acid (AA) treatments. The first one was sprayed with distilled water (control AA0), while, the second and third groups were sprayed with solutions containing 15 and 30gAA/L, respectively.The results concluded that HIT group had the highest embryo weight, embryonic mortalities and lower hatchability% compared to NIT group. The chicks weight (g) and triiodothyronine (T3) concentration were significantly lower (P≤0.05) in HIT group compared toNIT group. Glucose level and heterophil: lymphocyte (H: L) ratio wereincreased significantly (P≤0.01) as affected by thermal manipulations.The embryonic development, embryonic viability as well as hatchability improved by spraying ascorbic acid as compared to the untreated group.Values of glucose, T3, RBCs, PCV% and HGB were significantly increased in the blood of hatching chicks by spraying AA solutionas compared to control while, residual yolk and H: L ratio was significantly(P≤0.05) decreased by spraying AA solution . The embryonic development, internal organs%, PCV% and HGB has been affected by interaction between incubation temperature and ascorbic acid.
It could be concluded that, spraying eggs of Japanese quail exposed to heat stress with AA solutions (15 or 30 g/L) daily during4th to 14th days of incubation period, may be an alternative method to minimize embryos heat stress and maximize the embryonic viability as well as hatchability, immunity of hatched chicks and chick quality.