The Progesterone Concentration in the Plasma of the Goat During the Oestrous Cycle and Pregnancy

Abstract

SUMMARY Progesterone concentrations in the peripheral plasma of goats were measured by a protein-binding assay. The mean concentration was extremely low on the day of oestrus (0·2 ng/ml) and was not significantly different from that found in anoestrous or ovariectomized animals. The concentration increased to a maximum of 4 ng/ml on about day 10 of the 21-day cycle, and decreased rapidly during the last 3 days of the cycle. Plasma progesterone concentration during early pregnancy (2·5–3·5 ng/ml) was similar to the luteal phase value and remained steady from day 8 to day 60. Between days 60 and 70 there was a secondary increase in progesterone concentration which was maintained at this increased level (4·5–5·5 ng/ml) until just before parturition. In twin-bearing animals, the secondary increase was greater. Progesterone concentration decreased rapidly during the 1–2 days preceding parturition, but the concentration was still quite high on the day of parturition (1·25 ng/ml). The progesterone concentration in peripheral plasma was markedly increased during anaesthesia and the operation. After bilateral ovariectomy of the pregnant goat, peripheral progesterone concentration fell rapidly from 9 to 2·5 ng/ml during the first ½ h and then more slowly during the next 5–6 h. The animals aborted 36–48 h later. A consistent positive arterio—venous difference for progesterone was observed across the pregnant uterus in two unanaesthetized goats. These results indicate that the ovary is the main site of progesterone production in the pregnant goat and that production by the placenta is small and unlikely to influence the level of this hormone in the maternal circulation.

Progesterone, estrogen, LH, FSH and PRL concentrations in plasma during the estrous cycle in goat

“…The progesterone patterns we observed during the caprine estrous cycle were similar to those reported by Thorburn and Schneider (1972), Jones and Knifton (1972), Wentzel, Botha and Viljoen (1979) and Thibier, Pothelet and Jeanguyot (1981).…”

The Relationship Between Lactation and the Release of Prolactin and Growth Hormone in the Goat

“…In view of the inhibitory effect of high concentrations of progesterone on milk secretion in some species, it is interesting to note that the rise in the level of prolactin in the goat follows closely upon the sharp fall in the circulating level of progesterone which occurs 2 to 3 days before parturition (Thorburn & Schneider, 1972). Challis & Linzell (1971) have shown that during pregnancy in the goat the level of total oestrogen increased gradually 80 days before parturition, with a sharp increase just before parturition.…”

Oestrogen and progesterone concentrations in peripheral blood in pregnant red foxes (Vulpes vulpes)

“…(Short, 1961;Stabenfeldt, Osburn & Ewing, 1970) and goat (Thorburn & Schneider, 1971), while in others, there is a considerable increase in progesterone after implantation, e.g. in the ewe (Bassett, Oxborrow, Smith & Thorburn, 1969), coypu (Rowlands & Heap, 1966) and rat (Wiest, 1970).…”