Thyroid and thyrotrophic hormone levels in the blood of Friesian cows were determined during the oestrous cycle, at different months of pregnancy and 10 days after parturition. During the oestrous cycle there was an increase in the thyroid hormone level at oestrus accompanied by a decrease in the level of thyroidstimulating hormone. The thyroid hormone content of blood was low during dioestrus while the thyrotrophic hormone was high. No variation in thyroid hormone level was noticed during pregnancy, except for an increase during the 9th month. The level of thyrotrophic hormone was maintained at a comparatively high level during the first 4 months of pregnancy. After parturition the level of thyroid hormone was similar to that observed during dioestrus, while there was an increase in the level of thyrotrophic hormone.

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S U M M A R YBlood samples were collected three times weekly for 21 days before and after calving (day 0) from 29 buffalo cows and 22 buffalo heifers. Plasma concentrations of progesterone and total oestrogens were quantified by validated radioimmunoassays. Ovarian activity and uterine involution were monitored by rectal palpation at the sampling times and extended up to 60 days postpartum. The concentration of plasma progesterone in cows declined from 30 + 0-2 ng/ml (mean + s.E.) during days 21-17 before calving to 2-1 ±0-1 ng/ml at day -3, followed by a rapid fall during the last 3 days of gestation, reaching 1-2 + 0-3 ng/ml at the day of parturition. In heifers, plasma progesterone values increased slightly from 2-9 + 0-2 ng/ml at days 21-19 before parturition to 3-4 + 0-3 ng/ml by day -1 and then fell sharply to 2 1 + 0 1 ng/ml at calving time. During the postpartum period, plasma progesterone! decreased gradually and reached baseline values after day 15 postpartum, when the residual corpus luteum of pregnancy had completely regressed in all the animals studied. The plasma concentrations of total oestrogens started to increase at day -15 in cows and day -5 in heifers from below 40 pg/ ml to 122-5 ± 5 1 pg/ml for cows and 100-7 + 3-4 pg/ml for heifers by day -1. This was followed by a sharp increase to 251-2+17-3 and 240-5+10-1 pg/ml in these animals at the day of calving. Immediately after parturition, total oestrogens dropped abruptly to the lowest values and remained below 30 pg/ml in all cows and heifers until the end of the sampling period. We concluded that female foetuses significantly (P < 0-05) increased the maternal total oestrogens. Moreover, animals having postpartum disorders had significantly higher values for progesterone (P < 005) and lower values for total oestrogens (P < 001) than those having normal puerperal periods, but the magnitude of this difference varied in samplings between cows and heifers.

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