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An acute phase response has been identified during mid-gestation in bitches by determination of the serum C-reactive protein (CRP) concentration. In four pregnant bitches, a large increase in CRP during mid-gestation was followed by a second increase after parturition. In three pregnant bitches, a similar increase was observed during mid-gestation but the second (post parturition) increase was not detected. In two pregnant bitches only a small rise was observed in mid-gestation. No increase in CRP was observed in the serum of two bitches that were not mated following oestrus or in the serum of two bitches that were mated but did not become pregnant. One bitch was diagnosed as pregnant by palpation but did not produce a litter and did not have a mid-gestation increase in CRP. However, this animal did show an acute phase response shortly after oestrus.

Five pony mares were blood sampled during late pregnancy, foaling and early lactation. An homologous assay for horse prolactin was used to measure plasma prolactin concentrations in these samples. Regular estimates of cyclic activity were also made. Plasma prolactin concentrations rose markedly in the last week of pregnancy and remained high although variable in early lactation, before declining to basal levels by 1-2 months post partum. All mares showed a post-partum oestrus 7.0 +/- 0.9 days after parturition. One mare whose foal died shortly after birth showed a rapid decline in plasma prolactin values after death of the foal and an early oestrous period (4 days after parturition). The pattern of prolactin changes reported for the mare are in agreement with those reported for other mammalian species.

Results of preliminary investigations of fallopian tube patency in cattle using a method based on intrauterine instillation of PSP dye, and detection of the dye in the urine, suggest that this test can provide a useful diagnostic aid in cases of bilateral occlusion. In such cases PSP dye is not evident in the urine two hours later. In normal animals dye is present within 30 minutes. In two animals with unilateral blockage dye appeared at an intermediate time between the normal and bilaterally occluded cases. Repetition of the test and the use of adequate volumes of dye to cause uterine distension may be necessary to eliminate false negatives.

Summary. The uptake of 59Fe by rabbit placenta at different stages of gestation was determined, and subsequently the uptake of 59Fe by the subcellular fractions of the rabbit placenta during the last third of gestation was measured. The iron-containing compounds in the non-particulate fraction of the rabbit placenta during the last third of gestation were isolated and characterized.

Using a range of positive and negative sexual behaviour components, proceptivity of cycling, non-lactating mares and postpartum, lactating Pony mares was quantified around ovulation. Behavioural observations were compared to plasms concentrations of progesterone, total oestrogens and androstenedione. In addition, in cycling mares, comparison with plasma testosterone concentrations was carried out. Overall rejection behaviour by the mare was apparent both during dioestrus and during periods of basal plasma progesterone concentrations. Within cycling, non-lactating mares, and between postpartum ovulation associated with silent as opposed to overt oestrus, no consistent relationship existed between net behavioural scores and the circulating concentrations of oestrogens or androgens. The findings are taken to suggest that regulation of the signs of oestrus occurs to a large extent independently of circulating steroid concentrations.

Summary Six mares were studied over a period of two years under varying conditions of lighting from total darkness to normal ambient lighting. The mares continued to cycle during the winter under natural lighting and also when kept in total darkness. Circulating melatonin, progesterone and oestrogen concentrations were determined and related to clinical changes in the reproductive tract.

Plasma prolactin concentrations were measured in mares using an homologous radioimmunoassay. An annual rhythm in plasma prolactin was found, with concentrations higher during the summer than during the winter. In addition to this seasonal pattern, occasional high concentrations of prolactin were seen when concentrations were otherwise basal. Blood samples taken from mares during an oestrous cycle in October-November showed that prolactin values were basal for most of the cycle, with a marked rise in prolactin shortly before the onset of oestrus. This prolactin peak was associated with an increase in the size of the largest follicle, and with a peak of PGFM in some mares, but did not appear to be related to the LH surge. In oestrous cycles in March and May-June, there was a wide variation in the baseline of prolactin secretion, in accordance with the seasonal pattern already mentioned. However, the peak of prolactin seen around oestrus in October-November was less obvious in March and May-June. Post-partum mares showed a high but irregular profile of prolactin concentrations with no clear-cut pattern in relation to the oestrous cycle.

1. 1. The plasma clearance rates of 59Fe injected intravenously into sows is not increased as a result of pregnancy. 2. 2. The amount of iron transferred from sow to foetus during pregnancy is very small and represents less than 2 per cent of the iron injected into the mother. 3. 3. The pig placenta is able to synthesize ferritin. 4. 4. The haematology of the sow was normal whereas the foetus was anaemic as compared with other newborn animals. 5. 5. The results in the sow are compared with those obtained in the rabbit in which the foetuses have adequate iron stores at birth.