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W. C. WAGNER and WILLIAM HANSEL

Summary.

The mean interval to the first observed post partum oestrus was 14 days in milked cows. In contrast, none of eleven nursed animals showed behavioural oestrus by Day 30 post partum, although two ovulated before that time. Only one of seven anaemic animals (haemoglobin levels of 9 to 10 g/100 ml) showed behavioural oestrus by Day 22 post partum; two others ovulated, but showed no signs of oestrus. Thyroprotein-fed cows also had prolonged periods of post partum anoestrus.

Pregnancy corpora lutea were quite degenerate by Day 7 post partum. At Day 14 post partum, they were approximately 9·0 mm in diameter and remained at this size, at least to Day 30. There was an increase in follicular size following parturition. At Day 7, the mean diameter of the largest follicle was 9·6 mm; at Day 14, it was 11·3 mm; at Day 30, the largest follicle averaged 13·0 mm.

Neither the presence of suckling calves, nor anaemia delayed uterine involution. Caruncular tissue sloughed and was expelled from the uterus between Day 7 and Day 14 post partum. Regeneration of the surface epithelium over the caruncles occurred by growth from the surrounding tissue, and was complete in a majority of animals slaughtered at Day 30 post partum.

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F. N. THOMPSON and W. C. WAGNER

Summary.

Plasma corticosteroids were measured by competitive protein-binding techniques in the jugular and uterine venous plasma of parturient sheep. Plasma corticosteroids began to rise 48 to 72 hr ante partum in control ewes and were significantly elevated at parturition in both the control and ovariectomized ewes. Corticosteroid levels in adrenalectomized and adrenalectomized-ovariectomized ewes were markedly lower than in control ewes. Daily corticosteroid levels were frequently higher in the uterine plasma compared to the jugular plasma in all treatment groups. In sheep, the corticosteroid levels in immediate samples, however, were usually slightly greater in the uterine artery before the lambs were removed compared to those in the uterine vein. This concentration difference existed even when the plasma corticosteroid levels were significantly elevated in the umbilical circulation late in gestation when levels in the umbilical artery were slightly greater than those in the umbilical vein. It was concluded that fetal plasma corticosteroids are not transferred significantly to the maternal plasma in sheep during late pregnancy.

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F. N. THOMPSON and W. C. WAGNER

Summary.

Levels of progesterone were determined by competitive protein-binding techniques and oestrogens by radio-ligand binding techniques in the uterine and peripheral plasma of parturient ewes. Uterine progesterone levels began a continuous decline 4 to 5 days ante partum whereas jugular levels only declined 1 or 2 days ante partum. Peripheral plasma progesterone levels were significantly elevated in ewes carrying multiple fetuses compared to those in ewes with a single fetus. A similar but non-significant difference existed in the uterine plasma. Adrenalectomized and adrenalectomized-ovariectomized ewes had lower progesterone levels in the peripheral blood but not lower uterine levels than did control ewes. Ovariectomy did not affect progesterone levels. Oestrone and oestradiol values were lower in the uterine venous concentrations of adrenalectomized and adrenalectomized-ovariectomized ewes. A depression of oestrogen values before birth was not noted in ovariectomized ewes. It is concluded that the maternal adrenal has a definite rôle in oestrogen biosynthesis in pregnant sheep.

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W. C. WAGNER, RAYMOND SAATMAN and WILLIAM HANSEL

Summary.

There was a non-significant rise in pituitary lh concentration from Day 7 post partum (2·07 μg/mg fresh anterior pituitary) to Day 30 post partum (2·62 μg/mg). Neither nursing of calves nor anaemia caused a significant change in pituitary lh content. Both control and thyroprotein-fed non-post partum cows had significantly higher levels of pituitary lh, 7·4 μg and 6·9 μg respectively, than did the post partum cows.

There was no detectable tsh in pituitaries of five of six thyroproteinfed cows. tsh concentration ranged from 2·0 to 9·5 mu nih-tsh-b3/mg fresh pituitary in the remaining animals, but there were no significant differences between any of the groups. Thyroprotein-fed animals also had significantly lower thyroid cell heights than all other groups.

Adrenal data indicate a positive correlation exists between progesterone and cortisol in the same gland (r = 0·67, P<0·01). The only group difference of significance was that the nursed group had a significantly lower adrenal progesterone than did the milked group (0·63 versus 1·76 μg/g). Cortisol content was also lower in the nursed animals, but not to a significant extent.