Plasma thyroxine in the sow during pregnancy and lactation and during resumption of ovarian activity after weaning
Benjaminsen, E.
Acta Veterinaria Scandinavica 22(3-4): 369-381
1981
ISSN/ISBN: 0044-605X PMID: 7344527 Document Number: 169556
Total thyroxine [T4] in plasma was studied during pregnancy, lactation and during the post weaning period. Ovarian activity was monitored by progesterone determinations and estrous symptoms were recorded. In the 2 sows studied during pregnancy there was a distinct decrease in total T4 values in the last month of pregnancy, reaching a minimum about the time of farrowing. Total T4 values stayed low during lactation, but from about the time of weaning and during the following 2 wk the concentrations increased rapidly. There was no difference in the T4 pattern in sows resuming ovarian activity within normal time (days) after weaning (72 sows) compared with sows with delayed resumption of ovarian activity (19 sows). The T4 level after weaning did not differ between sows with silent heat and sows with overt estrus. Primiparous and pluriparous sows also had similar T4 values after weaning. Sows weaned in Jan.-June had slightly higher T4 concentrations after weaning than sows weaned in July-Dec. There was a significant negative correlation between number of suckling piglets and T4 concentrations before weaning. Free T4 index was calculated in some selected samples. The changes observed in total T4 apparently reflect changes in the free T4 concentrations.