Peripheral Plasma Progesterone Levels in Pigs During the Oestrous Cycle

Abstract

A rather consistent time interval (7 days) was observed between the decline in progesterone concentration and the onset of overt oestrus. The high levels of circulating progesterone in the gilt may suppress follicle development sufficiently during the luteal phase so that approximately 1 week is required between corpus luteum regression and ovulation.The concentration of plasma progesterone in nine castrated boars was 0\m=.\9ng/ml suggesting an extra-gonadal source of progesterone, possibly adrenal in origin.

Luteal function and oestrus in gilts treated with a synthetic analogue of prostaglandin F-2 (ICI 79,939) at various times during the oestrous cycle

“…In gilts in which complete luteal regression was induced, the onset of oestrus occurred 5-7 days after the initiation of treatment. This interval is similar to that observed between the onset of luteal regression and oestrus in the normal oestrous cycle (Stabenfeldt, Akins, Ewing & Morrissette, 1969;Henricks et al, 1972), after luteal enucleation (Anderson, Dyck & Rathmaker, 1966) or after the cessation of methallibure treatment (Polge, 1965). In the cow (Lauderdale, 1972;Rowson et al, 1972) and the mare (Allen & Rowson, 1973) oestrus occurs 2-4 days after PGF-2a treatment.…”

Relationship between peri-oestrus progesterone levels and time of ovulation by echography in pigs and influence of the interval between ovulation and artificial insemination (AI) on litter size

“…Thus, there is no evidence of a difference in the time of ovulation between gilts with natural or synchronised oestrus. The success rate in determining the time of ovulation by transcutaneous echography was 89.6% (26 out 29) in our study, a level Progesterone changes recorded around oestrus were similar to those previously reported by Stabenfeldt et al [31] and Soede et al [27]. A non-linear model was fitted to the progesterone levels, which allowed an objective determination of individual basal level and the variability of this basal level among females (SD).…”

Dioxin exposure and porcine reproductive hormonal activity

“…During this period growth of numerous follicles is initiated. Phase 2 lasts from day 9 to day 22 and can be divided into two periods: from day 9 to day 14, representing the period of maximal luteal activity, and from day 15, when the onset of luteal involution and follicular growth is accelerated (Stabenfeldt et al, 1969). The adult female ovary is a mass of follicles, corpora lutea, blood vessels, nerves, and connective tissue elements, all of which form a relatively heterogeneous array of histological units.…”