Foetal and Maternal Hormonal Changes Preceding Normal Bovine Parturition

Abstract

Successful chronic cannulation of the foetal posterior vena cava and maternal utero-ovarian and jugular veins in five Jersey cows between days 240 and 260 of gestation enabled changes in plasma hormone levels preceding calving to be monitored. All cows delivered live calves within the expected range of gestation for the breed.Corticosteroids were assayed by competitive protein-binding, and prostaglandin F, progesterone, oestrone and oestradiol-17\g=b\by radioimmunoassay. Foetal corticosteroids rose slowly from 5.0 \ m=+-\ 0.7 ng/ml at 20 days to 9.3 \ m=+-\3.0 ng/ml at 10 days before term, then progressively increased to a mean of 74 ng/ml at calving. Maternal levels remained relatively constant at 5 to 15 ng/ml, though higher concentrations occurred following surgery. Foetal oestrone and oestradiol-17\g=b\ concentrations were both less than 50 pg/ml and showed little change toward term. The maternal uteroovarian oestrogens increased slowly from 20 to 10 days pre-partum and then rose more rapidly reaching peak levels (2.9 \ m=+-\0.6 ng/ml for oestrone and 1.4 \ m=+-\0.3 ng/ml for oestradiol-17\g=b\) 1 to 4 days before delivery.Maternal progesterone concentrations fell towards term, with a rapid decrease over the last 36\p=n-\48 h. Prostaglandin F levels showed little change until 36\p=n-\48 h before calving when they gradually increased until the last 24 h where was a dramatic rise, reaching peak levels (5.7 \ m=+-\ 0.6 ng/ml) during labour.Changes in the plasma concentration of progesterone, oestrogen and cortisol in the prepartum cow are well documented. Calving is preceded by a decline in progesterone (Pope et al. 1969; Donaldson et al. 1970; Slabenfeldt et al.

A review of female cattle reproduction with special reference to a comparison between buffaloes, cows and zebu

“…A precipitous further decline to 0-4 ng/ml occurring 16-30 h before parturition has been recorded in blood samples taken every few hours. A similar temporal pattern has been found for cows (Schams et al, 1972;Hunter, Fairclough, Peterson & Welch, 1977;Kaker, Murray & Dobson, 1984). Increases in placental oestrogen synthesis occur in buffaloes, cows and zebu over the last 5-10 days.…”

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).…”

“…The relative contribution of the placenta and CL to maternal circulating progesterone at different gestational stages has not been determined. 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 more abrupt decrease in circulating progesterone 2-3 days prior to parturition is interpreted as being due to luteolysis and increased progesterone metabolism, likely precipitated by the increase in foetal cortisol production and release, a crucial component of the foetal endocrine signals that initiate parturition (Comline et al, 1974;Fairclough et al, 1975;Hunter et al, 1977).…”

Meloxicam Impact on Blood Plasma Cortisol Levels in Dystocia Affected Bovines

“…Cortisol is one of the most important member of the steroids from the stress point of view. The corticosteroid concentration rises in the plasma of the parturient cows at term and this dramatic rise is followed by sudden fall immediately after parturition (Adams and Wagner, 1970, Smith et al, 1973Hudson et al, 1976, Hunter et al, 1977Prakash and Madan, 1985). Prabhakar et al, (2002) assessed the degree of stress due to occurrence of dystocia and its correction by fetotomy and caesarean section by monitoring cortisol levels in dystocia affected buffaloes.…”