The hypothesis was tested that estradiol (E2) from the ovarian follicles controls time of luteolysis. Time of luteolysis was evaluated by multiple measures of corpus luteum (CL) structure (area, volume) and function (progesterone [P4], luteal blood flow). The hypothesis for experiment 1 was that repeated ablation of follicles would reduce circulating E2 and delay luteolysis. Heifers were randomly assigned on Day 9 (Day 0 = ovulation) to three groups. All follicles >or=4 mm were ablated on Day 9 (group FA9; n = 6); Days 9-15 (group FA15; n = 6); or Days 9-21 (group FA21; n = 7). As expected, follicular ablation delayed (P < 0.001) the rise in circulating E2 and peak E2 concentrations (FA9, Day 17.6 +/- 0.7; FA15, Day 20.3 +/- 0.3; FA21, Day 24.9 +/- 0.3). Luteolysis (based on each measure) was delayed (P < 0.005) by repeated ablation of follicles, with earlier luteolysis (based on P4 decrease) in FA9 (Day 15.2 +/- 0.8) than FA15 (Day 16.5 +/- 0.4), and a further delay in FA21 (Day 18.3 +/- 0.5). The hypothesis of experiment 2 was that exogenous treatment with E2 would stimulate prostaglandin F(2alpha) (PGF) secretion and prevent the delay in luteolysis associated with follicular ablations. Follicles >or=4 mm were ablated from Day 9 to Day 17 (n = 15). Heifers were treated on Days 13 and 15 with 1.0 mg of estradiol benzoate (FAE2; n = 7) or vehicle (FAV; n = 8). Treatment with E2 induced PGF secretion (detected by PGF metabolite) and induced earlier (P < 0.02) luteolysis in FAE2 than in FAV, whether determined by circulating P4 or by area, volume, or blood flow of CL. In summary, ablation of follicles (>or=4 mm) delayed and treatment with E2 hastened luteolysis in heifers with ablated follicles. Thus, these results are consistent with an essential role for follicle E2 in timing of luteolysis.

REPRODUCTION RESEARCHUterine blood flow and perfusion in mares with uterine cysts: effect of the size of the cystic area and age AbstractTransrectal color and power Doppler ultrasonography was used to study uterine blood flow and perfusion in mares with and without uterine cysts. Vascular perfusion of the uterus and blood flow velocities, vascular perfusion, diameter, circumference, and area of a cross section of the mesometrial attachment were evaluated. To study the effect of internal cysts, two matched groups (cystic and control, nZ21 mares/group) were used. Uterine vascular perfusion in mares with cysts was less (P!0.0001) in the cystic than the noncystic region and less (P!0.0009) than that for controls. Mares with cysts had lower (P!0.04) pulsatility index (PI) and greater end diastolic velocity (EDV; P!0.03) and time-averaged maximum velocity (TAMV; P!0.05) of the mesometrial vessels than the controls. To study the effect of the size of internal uterine cystic area, paired mares were arranged in four groups (nZ8-11/group): small uterine cystic area (%275 mm 2 ) versus controls and large uterine cystic area (O410 mm 2 ) versus controls. A small uterine cystic area did not affect uterine hemodynamics. Mares with large uterine cystic area had lower PI (P!0.05) and greater peak systolic velocity (P%0.05), EDV (P!0.009), and TAMV (P!0.005). To study the effect of age, old versus young mares without cysts were compared (nZ11/group). Old mares had greater EDV (P!0.02) and TAMV (P!0.01) than young mares. Results demonstrated, for the first time in any species, reduced uterine vascular perfusion in mares with uterine cysts and a positive association between size of the cystic area and disturbed uterine hemodynamics.

Several multiple-media culture systems have become commercially available for on-farm identification of mastitis-associated pathogens. However, the accuracy of these systems has not been thoroughly and independently validated against microbiological evaluations performed by referral laboratories. Therefore, the purpose of the present study was to evaluate the performance of commercially available culture plates (Accumast, Minnesota Easy System, SSGN and SSGNC Quad plates) to identify pathogens associated with clinical mastitis in dairy cows. Milk samples from the affected quarter with clinical mastitis were aerobically cultured with the on-farm culture systems and by two additional reference laboratories. Agreeing results from both standard laboratories were denoted as the reference standard (RS). Accuracy (Ac), sensitivity (Se), specificity (Sp), positive and negative predictive values (PPV and NPV, respectively) and Cohen’s kappa coefficient (k) of on-farm plates were determined based on the RS culture of 211 milk samples. All four plate-systems correctly identified ≥ 84.9% of milk samples with no bacterial growth. Accumast had greater values for all overall predictive factors (Ac, Se, Sp, PPV and NPV) and a substantial agreement (k = 0.79) with RS. The inter-rater agreements of Minnesota, SSGN, and SSGNC with RS were moderate (0.45 ≤ k ≤ 0.55). The effectiveness to categorize bacterial colonies at the genus and species was numerically different amongst the commercial plates. Our findings suggest that Accumast was the most accurate on-farm culture system for identification of mastitis-associated pathogens of the four systems included in the analysis.

Human chorionic gonadotropin (hCG) has been used to induce ovulation and as a luteotrophic agent in cattle. However, the effect of hCG therapy on the functional status of the equine corpus luteum (CL) is unclear. This study aimed to characterize the hemodynamic and secretory function of early CL of mares treated with different doses of hCG at distinct stages of the estrous cycle. Mares were assigned to nine experimental groups (n ¼ 6 mares/ group) according to dose of hCG and time of treatment. A single injection of one of three different doses of hCG (750, 1,500, or 2,500 IU) was performed in one of three distinct stages of the estrous cycle: preovulatory follicle !35 mm, day of ovulation (D0), or 48 hours after ovulation (D2). In addition, a control group treated with NaCl 0.9% was included in the study. The end points evaluated daily from D0 to D8 were area of the CL, luteal vascularity, number of colored pixels and total pixel intensity, and concentrations of plasma progesterone (P4). No effect (P > .1) of dose or time of treatment was observed for any end point, within each day. Luteal area did not differ throughout the days (P > .1), whereas Doppler parameters and concentrations of plasma P4 presented a progressive increase (P < .05) after ovulation in all groups. Secretory function and luteal hemodynamic were not affected (P > .1) by hCG dose and time of treatment. In conclusion, hCG therapy during estrus or early diestrus, at the doses tested, did not improve P4 secretion or luteal blood flow.

No abstract

Summary Six or 7‐day‐old equine embryos were divided into 4 groups; Group 1, n = 15, Day 7 embryos destined for immediate transfer; Group 2, n = 15, Day 6 embryos destined for deepfreezing with glycerol plus sucrose as cryoprotectant; Group 3, n = 10, Day 6 embryos destined for deep‐freezing with glycerol plus 1,2‐propanediol as cryoprotectant and Group 4, n = 3, fresh embryos destined for ultrastructural analysis. All the frozen/thawed embryos were transferred to recipient mares, except 3 embryos in Group 3 that were subjected to ultrastructural analysis. After thawing the cryoprotectants were removed by successive dilutions in PBS + 15% v:v fetal calf serum (FCS) containing decreasing concentrations of the cryoprotectants. Pregnancy was diagnosed ultrasonographically in 53.3%, 13.3% and 0% of the mares in Groups 1, 2 and 3 respectively. Ultrastructural analysis showed differences between frozen/thawed and fresh embryos. In the former, embryonic cells were deformed and showed dilation of the intercellular and perivitelline spaces, a decrease of desmosome number in the junctional complexes, few microvilli on the apical surface of the trophectoderm and an almost total absence of pinocytotic vesicles. Most of the mitochondria showed regions containing dilation and irregularities on the cristae, which appeared electron‐dense. The results obtained with Groups 2 and 3 embryos showed that the cryoprotectants employed were not effective in protecting the embryos against damage during freezing and thawing. Indeed, the ultrastructural changes observed in the Group 3 embryos explained the absence of any established pregnancies in this group of mares.

Changes in echotexture and blood flow in the wall of preovulatory follicles in heifers were studied in relation to the LH surge and ovulation in gonadotrophin-releasing hormone-induced (n = 7; Experiment 1) and spontaneous (n = 8; Experiment 2) ovulators. Ultrasonographic examinations and blood sampling were performed either every hour (Experiment 1) or every 6 h (Experiment 2). The interval from LH peak to ovulation in induced and spontaneous ovulators was 27.1 +/- 0.3 and 34.5 +/- 1.5 h, respectively. Follicle diameter did not increase between the LH peak and ovulation. In the induced ovulators, serration of the stratum granulosum was detected in one (14%), two (29%), three (43%) and four (57%) heifers at 4, 3, 2 and 1 h before ovulation, respectively. An initial increase in blood flow (P < 0.001) encompassed the LH peak in both experiments. In the induced ovulators, blood flow increased (P < 0.02) to maximum 3 h after the LH peak, maintained a plateau for 5 h, decreased (P < 0.05) between 9 and 14 h, increased (P < 0.05) again between 19 and 21 h and then decreased (P < 0.01) between 25 and 26 h (1 h before ovulation). The biphasic increase and decrease in blood flow and serration of the granulosum in the wall of the preovulatory follicle in cattle are novel findings.

In this study, endometrial samples were collected in 14 Nelore cows on days zero (ovulation), five, nine, thirteen and nineteen of the estrous cycle (biopsy group), and in 15 females these collections weren't performed (control group). Biopsies were done on the uterine horn endometrium contralateral to the ovary with corpus luteum. Blood samples were taken at -24, -16, -8, 0 +8, +16 and +24 hours in relation to progesterone drop (<1ng/mL, zero moment) and evaluated for 13, 14-dihydro-15-keto prostaglandin F2-alpha (PGFM) by radioimmunoassay (RIA). Plasma progesterone concentration was determined by RIA every 24 hours. Data were analyzed by ANOVA using the PROC GLM and MIXED of the SAS. The mean value for PGFM during the entire period evaluated was greater in the biopsy group. The mean concentration of PGFM at moment zero was not different between the groups; the mean concentration of PGFM was higher in the biopsy group before and after the drop in progesterone level. The maximum mean concentration observed was not different between the groups; however, the mean minimum concentration was different with high values in the biopsy group. Although the PGFM concentrations were higher in the biopsy group, the biopsy and control groups had similar length of estrous cycle showing that repeated endometrial biopsy on the side contralateral to the ovary with corpus luteum does not affect luteolysis and the length of the estrous cycle.