Urinary oestrogen levels in the sow during oestrous cycle and early pregnancy.

were characterized by a rise of the levels associated with oestrus to a well-defined peak followed by a sudden decrease, usually to the lowest levels observed. After conception, the levels of oestrone were not appreciably different from those during the oestrous cycle until at the end of the 3rd week at which time the excretion of oestrone increased. The week of maximal oestrone excretion in the three sows during early pregnancy lasted from Days 24, 25 and 27 after breeding. Consistent fluctuations during the oestrous cycle or after conception of urinary oestradiol-fraction Kober chromogens were not recorded.