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Summary The percentage of Technetium 99m‐albumin colloid (99mTc‐μAA), a radiocolloid, cleared from the uterine lumen within 4 h of intrauterine infusion, was measured in 15 mares during 2 consecutive cycles, on Day 3 of oestrus and 48 h after ovulation. Four nulliparous (Group 1) and 4 multiparous (Group 2) mares were classified as resistant and the remaining 7 multiparous mares were classified as susceptible (Group 3) to endometritis. Mares in Groups 1 and 2 cleared more 99mTc‐μAA from their uteri than did mares in Group 3 during oestrus (P<0.01) and 48 h after ovulation (P<0.001). In the Group 1 + 2 mares, >50% of the colloid was cleared in 7 and none in the remaining mare, apparently related to lack of cervical relaxation. Mean percentage of 99mTc‐μAA cleared by Group 3 mares was negligible (<5%), but some 99mTc‐μAA was cleared by 3 of the 7 mares during 4 of the 6 studies conducted. Clearance of radiocolloid infused into the uterus of 3 reproductively normal mares during dioestrus was negligible. 99mTc‐μAA infused into the uterus did not adversely affect endometrial integrity as determined by endometrial biopsy. Mares tolerated the procedures well. We conclude that scintigraphy can be used to detect impaired mechanical clearance of the uterus: reproductively normal mares clear >50%99mTc‐μAA within 2 h of infusion whereas those susceptible to endometritis or mares with poor cervical dilatation may exhibit delayed uterine clearance.

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Fetal maturation and the timing of parturition in both sheep and primates are thought to be controlled by the hypothalamic-pituitary-adrenal axis but little is known about the endocrinology of the equine fetus. We investigated the ontogeny of plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol and corticosteroid binding capacity in the late-gestation fetal horse. We also wished to determine whether there is ultradian rhythmic release of ACTH and cortisol in fetal horses and we compared fetuses to maternal and non-pregnant adult horses. Six fetuses, 278-304 days gestation (term approximately 335), were catheterized and sampled daily until delivery. Mean (+/- S.E.M.) ACTH concentrations increased significantly from 159 +/- 21 to 246 +/- 42 pg/ml over the last 2 days before parturition. Fetal cortisol increased significantly from 3.1 +/- 1.0 to 13.4 +/- 3.7 ng/ml (mean +/- S.E.M.) over the last 9 days before delivery. The slope of regressions for ACTH and cortisol concentrations with respect to time were positive in all subjects and statistically significant in 3 of 6 for ACTH and 5 of 6 for cortisol. Fetal corticosteroid binding capacity declined from 49.5 +/- 20.5 to 16.1 +/- 2.2 ng/ml (mean +/- S.E.M.) over the last 10 days before parturition. However, the greatest changes in ACTH, cortisol and corticosteroid binding capacity occurred very late in gestation, during the last 48 to 72 h before parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

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SummaryFoals are born essentially agammaglobulinemic and rely on the absorption of colostral IgG for protection against infectious agents during the first few weeks of life. A mare produces colostrum during the last 2 to 3 weeks of gestation and once the foal suckles, it is rapidly depleted. Colostral quality is directly related to its specific gravity and the amount of immunoglobulin it contains can be estimated with an equine colostrometer or sugar or alcohol refractometers. Foals whose dams do not have adequate colostrum need to be supplemented with a substance rich in immunoglobulin. Equine colostrum is highly preferred as a substitute over bovine colostrum or commercial immunoglobulin products because the IgG is most readily absorbed. Failure of passive transfer can be estimated in the foal as early as 8 to 10 hours of age. There are a variety of assays that may be used in the field to rapidly estimate the immunoglobulin content in the foal. Foals with low serum IgG concentrations should receive additional IgG within the first 3 days of life. The well-being of foals with failure of passive transfer will depend greatly on the farm environment. Foals living in a clean, well ventilated barn that is not crowded are less likely to become ill than foals born into dirty, crowded conditions. Keywords:equine, foal, immunology, passive transfer, immunoglobulins

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