Characterization of electrolytes and protein content in isthmic and uterine flushings from hens laying shell-less...

In Experiment 1, hens laying hard-shell (HS) eggs were sacrificed at each of eight stages of egg formation including oviposition (0 h) and 1, 4, 8, 12, 16, 20, and 24 h after oviposition. In Experiment 2, hens laying either shell-less (SL) or HS eggs were sacrificed at four stages of egg formation (oviposition, 4, 8, and 20 h after oviposition). The isthmus and uterus were flushed with 6 and 10 mL of cold .85% NaCl, respectively, and electrolyte contents were determined. Total flushing contents of calcium, potassium, and magnesium were higher (P less than or equal to .01) in uterine than in isthmic flushings (Experiment 1). In every case, an interaction (P less than or equal to .01) between time of collection and organ (isthmus and uterus) was found, indicating that patterns of change in flushing content of each electrolyte differed in the two organs over time in birds laying HS eggs. In Experiment 2, total recoverable calcium, magnesium, potassium, and total protein were higher in uterine than isthmic flushings (P less than .01). Interactions between time of collection (0, 4, 8, and 20 h) and treatment group (SL or HS) were observed for all electrolytes measured in uterine flushings. Results suggest that calcium, required for shell calcification, does not appear in the isthmic or uterine lumen or both at an appropriate time in SL hens. Thus, production of SL eggs may be related to mechanisms regulating patterns of change or ratios of electrolytes (calcium, magnesium, potassium) or both in the isthmus or uterus of the laying hen.