Daily Egg-Cycle in Japanese Quail: Serum Biochemistry, Bones, and Oviduct Changes

This study described changes in the serum biochemistry, morphology of genital organs, long bone, and eggshell during the daily egg formation cycle in Japanese quails. Sixty quails (18-wk) were distributed in 6 groups according to hours post-oviposition (POV): 0 hr POV (16h00), 2 hrs POV (egg in magnum), and 4, 8, 14, and 20 hrs POV (egg in uterus). The magnum had higher relative weight before the next ovulation (20 and 0 hr POV), and its tubular glands showed functional variation through periods: abundant eosinophilic, PAS+, and negative Alcian blue secretion at 0 and 2 hrs, empty glands aspect at 4 hrs, and filled again at 20 hrs POV. Serum albumin and total Ca had the highest value in the 2 hrs group, and the lowest in 8 and 14 hrs groups. Egg-cycle period affected the Ca% of the medullar bone of the femur and tibiotarsus, with the lowest mean at 14 hrs POV (06h00), and the highest mean after oviposition (0 hr POV), showing the recovery of Ca stores in long bones for the next egg cycle. Analysis of the eggshell using scanning electron microscopy evidenced that palisade layer formation starts during the night (8–14 hrs POV), and most parts are secreted during the day period. In conclusion, eggshell secretion in light periods, high magnum activity and medullary bone Ca deposition during midday and afternoon, as well as the ovulation/oviposition in the afternoon, are the main characteristics of the distinct physiological aspects of the egg cycle in quails.