Peripheral Plasma Levels of Oestrogens and Progesterone During Late Bovine Pregnancy

Abstract

The peripheral plasma levels of oestrone* were measured in 127 dairy cows of the Swedish Red and White Breed. The levels recorded during the time period from the 20th to the 35th week of pregnancy were below or about 0.1 ng per ml. After the 35th week of pregnancy the levels increased gradually and maximum levels ranging from 0.5 to 2 ng per ml were found during the last week of gestation. After parturition the levels decreased significantly to about 0.1 ng per ml or less. Six cows were sampled daily from 8 days before until two days after parturition. The peripheral plasma levels of oestrone, oestradiol-17β and progesterone were measured. The oestrone level ranged from about 0.7 to 0.9 ng per ml during the last eight days preceding the delivery. The peripheral plasma levels of oestradiol-17β followed the same pattern as for oestrone. The concentration of oestradiol was only 10 to 20 per cent of the oestrone level. The mean peripheral plasma levels of progesterone were about 4 to 5 ng per ml during the last seven days before partus. A significant drop of the peripheral plasma level of progesterone to an average of 1.8 ng per ml occurred about 24 hours before parturition.

Role of the adrenals in the maintenance of pregnancy in cows

“…However, the changes in concentrations of the two oestrogens are approximately parallel immediately before parturition with oestrone rising earlier and remaining higher (Smith, Edgerton, Hafs & Convey, 1973 ;Chew et al, 1979a). The pre-partum levels of oestradiol-17ß in control and adrenalectomized cows were similar to those reported by Edqvist, Ekman, Gustafsson & Johansson (1973), Smith et al (1973) and Robertson (1974) Estergreen et al (1967) and Chew et al (1979a). Under the conditions of the present experiment, the cows with retained placentas (ovariectomized and ovariectomizedadrenalectomized groups) had lower peripartum levels of progesterone and oestradiol-17ß than did cows without retained placentas.…”

Multilevel regulation of steroid synthesis and metabolism in the bovine placenta

“…At mid-gestation, the progesterone levels drop slightly from about day 100 to 180, and then rise slightly at around day 200 (Stabenfeldt et al, 1970, Morrow and Lee, unpublished data). The levels start to decline gradually from about 60 days pre-partum, then abruptly from about 2 days before delivery of the calf (Gomes and Erb, 1965;Stabenfeldt et al, 1970;Edqvist et al, 1973;Smith et al, 1973;Hunter et al, 1977). The withdrawal of progesterone near parturition is a prerequisite for normal calving Taverne et al, 2002).…”

“…Progesterone and oestrogen profiles in bovine pregnancy. Schematic representation of the dynamic changes in the concentrations of progesterone, oestrone, and oestrone-sulphate in maternal blood during bovine pregnancy (adapted with data from Stabenfeldt et al, 1970;Edqvist et al, 1973;Smith et al, 1973;Echternkamp, 1992;Dobson et al, 1993;Hoffmann et al, 1997;Patel et al, 1999;Takenouchi et al, 2004). pregnancies with two or more foetuses than in pregnancies with a single foetus (Echternkamp, 1992;Dobson et al, 1993;Patel et al, 1999;Hikaro et al, 2002). The profiles represented in Figure 1 and described below are for singleton pregnancies.…”

“…The decline in progesterone concentration in late gestation is either due to increased metabolism or withdrawal of an unidentified luteotrophin Hunter et al, 1977). Some authors attribute the decline of progesterone concentration in the month before birth to a decline in placental progesterone production pre-partum (Edqvist et al, 1973;Kindahl et al, 2004). Because this coincides with an increase in circulating oestrogens, it was suggested that pregnenolone, the common precursor substrate for the synthesis of both steroids, is diverted from progesterone to oestrogen synthesis (Schuler et al, 1994).…”

“…The placenta is the main source of oestrogens in the bovine pregnancy (Edqvist et al, 1973;Peterson et al, 1975;Hoffmann et al, 1976). Both oestrone and oestradiol were detected in cotyledonary and caruncular tissues from about the fourth month of gestation (Tsumagari et al, 1993).…”