Changes in Inorganic Phosphorus Levels in Shell Gland Fluid during the Oviposition Cycle and at Progesterone-and Acetylcholine-induced Oviposition in the Hen.

Abstract

The secretion of shell gland fluid and inorganic phosphorus concentration in the fluid were examined in regularly laying hens and progesterone- and acetylcholine-treated hens. In normally laying hens, the rate of secretion of the fluid decreased as the time goes to oviposition, and phosphorus concentration in the fluid increased near the time of oviposition. A significantly negative correlation (P<0.01, r=-0.77) was found between the rate of fluid secretion and phosphorus concentration in the fluid.In progesterone-treated hens, which showed premature oviposition followed by ovulation, the secretion rate of the fluid was significantly (P<0.01) lower and phosphorus level in the fluid was significantly (P<0.05) higher than those in control hens.On the other hand, in the case of acetylcholine-treated hens, there was no significant difference in the rate of fluid secretion and phosphorus concentration in comparison with control hens despite the fact that premature oviposition was induced by the treatment with this reagent, but in this case no ovulation was observed after induced oviposition. The results obtained from this experiment suggest that a decrease in the rate of fluid secretion and an increase in phosphorus concentration in the fluid near the time of oviposition might be regulated by the factor(s) which is concerned with ovulation, rather than oviposition associated with the contraction of uterine muscle.