112 INFLUENCE OF LOW-VOLUME UTERINE FLUSHING ON UTERINE VASCULAR PERFUSION AND ENDOMETRIAL THICKNESS DURING EARLY DIOESTRUS IN BEEF CATTLE

Abstract

The relevance of the uterine secretions during early embryonic development is due to its role as the only source of nutrients for embryo prior to implantation. Probing of the uterine secretions during early pregnancy without compromising gestation would be an important tool for the identification of fertility markers. Manipulations of the uterus could lead to a local increase in blood flow, which could result from the physical stimulation or tissue damage and inflammation. This study aimed to evaluate the effects of low-volume flushing of the uterine horn contralateral to the ovulation on uterine vascular perfusion and endometrial thickness 6 days after artificial insemination (AI). Transrectal B-mode and color Doppler ultrasonography (MyLab30 Vet Gold; Esaote Healthcare) were used to compare changes on endometrial thickness and uterine vascular perfusion, respectively. Examinations were carried out on 15 Nelore cows just prior to the flushing procedure (0 h), 6 and 24 h later. Cows were inseminated after oestrus detection and uterine flushings were performed 6 d after AI. The uterine horn, contralateral to the corpus luteum, was flushed with 20 mL of PBS using a Foley catheter. After massage of the uterine horn, flushing was collected in a syringe by suction. Vascular perfusion was estimated by scoring the extent of colored areas within the endometrium and mesometrium. Vascular perfusion scores indicated nil (1), minimal (2), intermediate (3), and maximal (4) vascular perfusion. Endometrial thickness was measured by taking the maximum diameter and its perpendicular diameter; these values were summed and then divided by four. Data that were not normally distributed were transformed to natural logarithms or ranks. For each variable, the main effect of side (flushed and nonflushed horns), hour, and their interaction were analyzed using the PROC MIXED procedure from the SAS software. The least significant difference method was used for the comparison of means among hours. An hour effect was detected for endometrial and mesometrial scores of vascular perfusion (Table 1), representing an increased vascular perfusion about 6 h after the flushing procedure and a return to basal perfusion at 24 h. Results indicate that the unilateral flushing procedure increases vascular perfusion on both uterine horns. For endometrial thickness, no effect of side, hour, or their interaction was detected. In conclusion, unilateral low-volume uterine flushing results in a transitory increase in uterine blood flow about 6 h post-flushing. Further studies are needed to evaluate other inflammatory characteristics and the potential effect on pregnancy rate in response to the uterine flushing procedure performed during early pregnancy.

Table 1.  Scores of endometrial and mesometrial vascular perfusion and endometrial thickness of both uterine horns at the time of uterine flushing (0 h), 6 and 24 h post-flushing (mean ± standard error of the mean)