SUMMARY

The plasma 17:21-dihydroxy-20-keto-corticosteroid levels in the cow in late pregnancy (33-0 days before calving) are only slightly higher than in the cow soon after calving (0-99 days). A larger rise was sometimes seen in the last few days before calving. Except in one case where calving was difficult, no evidence of increased levels associated with the time of labour was found. Higher levels in the first day or two after calving were seen in some cases, but subsequently levels were uniformly low\p=m-\thedifference from earlier levels being statistically significant(P=0\m=.\01). In general, these results are in contrast with the human picture. Possible reasons for these findings are discussed. Cortisol is known to be secreted by the bovine adrenal cortex [Hechter, Zaffaroni