Hormonal interrelationships in postpartum suckled dairy cows
Madej, A.; Oyedipe, E.O.; Edqvist, L.E.; Kindahl, H.
Acta Veterinaria Scandinavica 33(4): 261-271
1992
ISSN/ISBN: 0044-605X PMID: 1488942 Document Number: 392031
Three cross-bred cows calved in March and April and were studied until day 62 after parturition. Each animal suckled 2 calves ad libitum. All calves were removed from the cows on day 55 after parturition. Blood was collected 3 times per day from the jugular vein by venipuncture. On 4 occasions after parturition (days 7-8, 21-23, 35-36 and 49-50) the cows were bled through a jugular venous catheter every 30 min during 24 h. The plasma samples were analyzed for 15-keto-13,14-dihydro-PFG2 alpha (the main PGF2 alpha metabolite), LH, prolactin, cortisol and progesterone by radioimmunoassays. The concn of PGF2 alpha increased from 280 to 730 pmol/litre within the last 4 days before parturition. The highest geometric mean was 3106 pmol/litre on the day of parturition. Thereafter a steady decrease of PGF2 alpha metabolite concn was seen until day 21 when, it reached a plateau at 148 pmol/litre. In all cows the plasma LH concn increased significantly from about 1.6 micro g/litre on days 7-8 to 2.4 micro g/litre on days 21-22 post partum. The frequency of LH pulses showed no tendency to increase as the postpartum period progressed and averaged 6.5 pulses/24 h. Mean plasma LH concn increased from 2.1 micro g/litre 2 days before weaning to 3.2 micro g/litre 2 days after weaning. LH peaks occurred less frequently in association with prolactin and cortisol peaks than in their absence. A partial positive correlation between PGF2 alpha metabolite and cortisol was found on days 7-8 post partum. Correlation between prolactin and cortisol on day 7-8 and 21-22 post partum was also positive. There was a negative correlation between LH and cortisol on days 7-8 and days 49-50 post partum. The first short progesterone increase observed after weaning was terminated in conjunction with PGF2 alpha metabolite peaks.