Gestational Length and First Postpartum Ovulation of Criollo Mares on a Stud Farm in Southern Brazil

The Criollo horse industry requires more efforts toward a better understanding of breed characteristics and physiology; few studies have been conducted in Criollo horses to fulfill this demand. Toward this aim, 70 Criollo mares (between 3 and 28 years of age) underwent physiologic evaluation of the length of gestation, occurrence of foal heat, and interval to postpartum ovulation. Gestation length in the 70 mares was 335.6 ± 10.5 days, varying from 312 to 364 days. The mean (±SD) interval from parturition to first ovulation of 42 mares that foaled between September and December of 2005 and 2006 was 19.9 ± 14.0 days. Eighty-three percent of the mares had an interval to foal heat ovulation shorter than 20 days (35/42). The mean (±SD) parturition to ovulation interval of these mares was 14.2 ± 3.0 days.     

Hematological and Biochemical Profiles in Peripartum Mares and Neonatal Foals (Heavy Draft Horse)

Peripartum mares and neonatal foals are physiologically unstable. Although hormonal changes around the parturition have been well studied in the field of endocrinology, hematological and biochemical changes have been studied little. The purpose of this study was to examine hematological and biochemical changes in peripartum mares and neonatal foals (n = 23; heavy draft horse). The number of white and red blood cells, hemoglobin concentration, hematocrit, mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration, platelet count in peripheral whole blood, and the concentration of glucose, nonesterified fatty acid, total cholesterol, triglyceride, total protein, albumin, globulin, blood urea nitrogen, creatinine, aspartate aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, creatine kinase, iron, calcium, inorganic phosphate, magnesium, sodium, potassium, and chlorine in serum were measured. The main changes observed in peripartum mares suggested the following: (1) dehydration at the foaling, (2) physical stress by the foaling, (3) muscle damage by the foaling, and (4) change of energy metabolism associated with the beginning of lactation. The main changes observed in neonatal foals suggested the following: (1) dehydration (hemoconcentration) at the birth, (2) intake of colostrum, (3) beginning of urination, (4) functional change of hematopoiesis, (5) change of liver metabolism associated with the beginning of enteral nutrition, and (6) change of milk composition. This study revealed hematological and biochemical dynamics in peripartum mares and neonatal foals.     

West Nile Virus Antibody Titers and Total Immunoglobulin G Concentrations in Foals from Mares Vaccinated in Late Gestation

This study was conducted to determine whether prepartum vaccination of mares would enhance passive transfer of West Nile virus (WNV)-specific antibodies and to characterize the pattern of decline for maternally derived WNV antibodies in foals. Seventeen light horse mares were allocated to WNV or control treatments. At 30 days before expected foaling, mares were vaccinated for encephalomyelitis, tetanus, herpesvirus, and influenza. At this time, WNV mares were vaccinated with a killed WNV vaccine. Blood samples were taken from mares 30 days before expected foaling, from mares and foals within 24 hours of foaling (0 days), and from foals at 7, 30, 60, 90, 120, 150, and 180 days of age as well as 30 days after an initial (PV1) and subsequent (PV2) WNV vaccination. Serum was analyzed for titer to WNV and total immunoglobulin G (IgG). Although WNV titer did not change over time in control mares, an increase (P < .05) was observed in WNV titer for WNV mares vaccinated 30 days before expected foaling. Foals of WNV dams had greater (P < .05) WNV titers than foals of control dams. Mean WNV titers of all foals increased from 0 to 7 days and declined through 180 days of age. Total IgG of foals increased from days 0 to 7, declined from days 30 to 120, and increased from days 150 through PV2. These results suggest that vaccination of mares for WNV in late gestation has a beneficial effect on foal WNV titer.     

Retained Fetal Membranes in Heavy Draft Mares Associated with Histological Abnormalities

Retention of fetal membranes is one of the most common life-threatening peripartum problems; however, its etiology is still unknown. Draft mares are more likely to retain fetal membranes than other breeds of mares. Because a strong connection between the fetal membranes and the endometrium has been observed in cases of retention, we studied the changes in the endometrium and the allantochorion of heavy draft mares with this condition. Tissue samples were taken from 90 mares that retained the fetal membranes and from 21 that did not. Retained fetal membranes were associated with adhesion of the allantochorion to the endometrium in 88% of the mares; this adhesion depended on the following factors: occurrence of fibrosis both in the lamina propria of the allantochorial villi and in the allantochorial stromal connective tissue, overdevelopment of the allantochorial stromal connective tissue, oversized allantochorial epithelial cells, and sparser and less-branched allantochorial villi.     

Proliferation and Apoptosis in Fetal Membranes and Endometrium During Placental Retention in Heavy Draft Mares

Placental retention (retained placenta [RP]) is a serious and common peripartum disease in mares, but the etiology and pathogenesis of RP still remain unclear. The alteration of cell proliferation and apoptosis is considered to be an important factor in RP. Fetal membranes and endometrial biopsies were collected from mares with RP (n = 8) and from control mares (n = 10). The proliferation and apoptosis levels in the chorionic and the endometrial epithelia were assessed by proliferating cell nuclear antigen immunostaining and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, respectively. The study revealed that there was an insignificant decrease in proliferation and a significant increase in apoptosis in the chorionic epithelium from mares with RP. This result excludes a proliferation imbalance from the possible causes of RP. In the area of the nonpregnant horn of the placenta, proliferation was negatively correlated and apoptosis was positively correlated with the degree of fetomaternal anchorage. It was observed that, in all mares with placental retention, the endometrial epithelium (both luminal and glandular) showed decreased proliferation and increased apoptosis, which may indicate a delay in postpartum uterine regeneration.