Uterine involution in colombian fine pace mares, measured by ultrasonography and endometrial cytology

Abstract

Today, there still exists a controversial issue, as to the high incidence of early embryonic death in mares, mated on the first post partum oestrus. The purpose of this study was first, to determine the post partum period of uterine involution in fine pace Colombian mares using endometrial cytology and ultra sonograph. Secondly, to determine the relation between the neutrophil percentages found in cytology and the echogenicity of accumulated intrauterine fluid during the first 30 post partum days. Twenty (n=20) mares were examined beginning on the 6th post partum day and on alternate days, up to the 30th day. All subjects were grazing Kikuyo grass (Pennisetum clandestinum) at la Sabana de Bogotá, 2.600 meters over sea level, 4 º north latitude and with an average temperature of 13 º C. From the 3rd postpartum day, all 20 mares were exposed to 2 healthy stallions, to establish their heat behaviour. Ten of them, following complete randomization, were inseminated on the first postpartum heat, while the others were inseminated on the second post partum heat. Genital examination was carried out by a technician, who did not know the reproductive history of any of the experimental mares. Examinations included rectal palpation, ultra sonograph (Pie Medical 48 linear array, 5 MHz), vaginal swabs and endometrial cytology. Uterine dimension was recorded by rectal palpation and ultra sonograph, it was included the uterine horn dimensions (tip, middle, and corporo-cornual junction) of previously gravid and non gravid uterus. Intrauterine fluid detection was performed by the use of an echogenicity scale. Ovaric structures were recorded (preovulatory follicles and ovulation). Pregnancy diagnosis was performed on day 15 post ovulation and then confirmed on day 40. Endometrial cytology samples were taken from uterus after the perineal area was disinfected using non covered isopos with a Pollanski speculum. Smears specimens were fixed with metil alcohol for 15 minutes and stained with Giemsa for 20 minutes. Anatomic uterine involution (means decreased size of pregravid horn) was completed on day 24 (range 12-30 days). Intrauterine fluid was seen by ultrasonography between day 6 and 18 post partum. Neutrophils and endometrial cells necrotic or not, constituted 80 % of the cell population. Neutrophils and cellular necrosis had a linear decrease beginning on day 9 post partum, in opposition, on this day the endometrial cell type pattern had a linear increase. The percentage of lymphocytes and eosinophils remained low and constant during the period of the study. A positive and significant correlation (r=0.83, P<01) was found between the accumulated uterine fluid observed by ultra sonograph and neutrophil cells analyzed in endometrial cytology. Based on this finding, it is suggested that the cellular component of the fluid encountered alters the echo pattern on uterine examination. Mares that did not show much intrauterine fluid accumulation and had low percentage of neutrophil counts (4 % or less) during first postpartum heat, had a better conception rate than mares with high neitrophils percentage. Foal heat was observed on day 7 ± 2.8 (S.D.), second post partum heat was detected on day 24 ± 2.8 (S.D). Conception rate was 30 % and 50% respectively, on first and second post partum heat. It is concluded that endometrial cytology and ultra sonograph are helpful diagnostic methods to study uterine involution in post partum mares. These techniques help the reproductive technician to establish a valid criterion regarding when to mate a mare that has a calf.