Impact of probing the reproductive tract during early pregnancy on fertility of beef cows

This short communication reports the impact of endometrial biopsies, uterine flushings and follicular fluid aspiration procedures at day 6 post artificial insemination (AI) on pregnancy rates. In Experiment 1, cows were timed AI (TAI) and assigned to the following treatment groups: control (n = 37), uterine flushing (n = 35) and endometrial biopsy (n = 38). On day 30 post AI, pregnancy rates were 40.5%, 33% and 28.5%, respectively (p > 0.1). Pregnancy rate on day 60 was lower (p < 0.004) in flushed cows than in the controls. In Experiment 2, oestrus was detected and cows were assigned to flushing (n = 32) or biopsy (n = 33) treatments 6 days after AI, which resulted in pregnancy rates of 31% and 36%, respectively (p > 0.1). In Experiment 3, cows were, 6 days after TAI, randomly assigned to the following treatments: control (n = 84) or aspiration of the largest follicle (n = 73). Pregnancy rates on day 30 post AI were 63.5% for the control group and 53% for the aspirated group (p > 0.1). In conclusion, uterine flushing and endometrial biopsy negatively affect pregnancy rates, but neither procedure can be considered to be incompatible with pregnancy maintenance. Follicular aspiration during pregnancy does not interact with pregnancy success. The amount and quality of samples obtained are compatible with the use of cellular and molecular analysis of uterine variables from cows that failed or succeeded on maintaining pregnancy.

168 INFLUENCE OF SEVERAL INSULIN PLASMA CONCENTRATIONS ON PROGESTERONE PRODUCTION AND HISTOLOGY OF CORPORA LUTEA IN SUPEROVULATED EWES

Nutritional status is essential for the determination of mammalian reproductive performance, and insulin is one of the main indicators for such condition. This hormone is able to interfere, directly or indirectly, with CL function, leading to alterations in steroidogenic capacity and cell development and, consequently, early embryonic development. The aim of this work was to identify CL histological alterations caused by different insulin plasma concentrations in superovulated ewes, as well as their interference in CL progesterone production. Santa Inês ewes (n = 24, 4 years old) were divided into 3 treatments: control (T1, n = 9); hypoinsulinemic (T2, n = 6), and hyperinsulinemic (T3, n = 9). In order to become hypoinsulinemic, ewes were treated with a single dose of alloxan monohydrate (50 mg kg-1 i.v; Sigma-Aldich, St. Louis, MO, USA) 48 h before the beginning of the superovulation protocol, whereas the hyperinsulinemic group was treated with administrations of 20 IU of NPH human insulin at every 12 h (Biolin-N; BIOBRAS, Montes Claros, Brazil). All animals were fed corn silage and minerals ad libitum. Animals had their estrus synchronized with vaginal pessaries containing medroxyprogesterone acetate (60 mg) and were superovulated with porcine FSH (250 IU, PLUSET®, Calier, Spain) and eCG (250 IU, Novormon®, Schering-Plough, Kenilworth, NJ, USA), in a 13-day protocol. After removal of vaginal pessaries, blood samples used for quantification of progesterone and plasmatic insulin by radioimmunoassay were collected daily at 0700 h until the day before embryo recovery. Hysterectomy was performed in all groups after embryo recovery (T1: n = 3, T2: n = 6, and T3: n = 4), and ovaries were placed in buffered formalin saline. CL histological sections were evaluated by hematoxylin/eosin staining. Results were assessed by SAS statistical analysis software, using the MIXED procedure (SAS Institute Inc., Cary, NC, USA). Mean values were compared by Tukey’s test. The mean CL number was lower in T2 (5.0 ± 2.7; P < 0.05) compared with T1 (10.2 ± 5.1) and T3 (11.3 ± 3.0) animals. No histological differences were observed between treatments T1 and T3. However, CL within the T2 group had a higher number of cells with picnotic nuclei and strongly contracted eosinophilic cytoplasm. Such alterations are suggestive of cellular apoptosis. The T2 group also differed for P4 production (P < 0.01) from the second (T2: 2.23 ± 0.71 ηg mL-1; T1: 5.42 ± 4.01 ηg mL-1; T3: 6.44 ± 2.76 ηg mL-1) to the sixth day post-estrus (T2: 7.58 ± 7.00; T1: 24.79 ± 8.40; T3: 32.07 ± 0.85 ηg mL-1). The mean insulin plasma concentration differed between treatments (P < 0.01); higher concentrations were obtained in the T3 group (20.05 ± 7.50 μIU mL-1), whereas the T2 group had lower concentrations (10.18 ± 3.57 μIU mL-1) compared to controls (T1: 14.52 ± 3.80 μIU mL-1). In conclusion, low plasma concentration of insulin may restrict the response to superovulatory treatment and cause CL histological changes, suggesting a reduction in cell activity due to premature cellular senescence.