Portal de Pesquisa da BVS Veterinária

Acta sci. vet. (Impr.); 40(4): Pub. 1072, 2012. ilus, tab, graf

Artigo em Português | VETINDEX | ID: biblio-1377693

Resumo

Background: The early embryo development is affected by the progesterone concentration, especially on the first weeks after conception. It's well known that the size and weight of corpus luteum (CL) is positive correlated with higher progesterone production. The use of treatments that increase luteal function in different periods after fixed timed insemination (FTAI) has been tested recently, aiming better embryo survival rates and pregnancy establishment. The objective of this experiment was evaluate the effect of treatment with hCG or eCG 7 days after FTAI on the development of the CL, follicle growth and pregnancy rate in beef cows. Materials, Methods & Results: Two hundred and nineteen Brangus cows were synchronized to FTAI using intravaginal implants containing 1g of progesterone for 8 days and injecting 2 mg of estradiol benzoate (EB), on the first day of treatment. All cows received 150 mcg of D-Cloprostenol, i.m., on Day 8 and 24 h after, 1 mg of EB, i.m. The timed AI were done 52-56 h after the implant removal. Seven days after the AI the cows were randomly assigned in 3 different groups according the treatment. hCG (n = 40) receiving 1500 IU of hCG, i.m.; eCG (n = 41) injection of 400 IU of eCG, i.m., and Control (n = 138). The ultrasonographic examinations were done on days 0, 7 and 12 to determine the presence and diameter of follicles, area of CL on the subgroups hCG (n = 26), eCG (n = 26) and Control (n = 14). The pregnancy diagnosis was done 30 days after FTAI and another exam was done 60 days after FTAI only on the cows that were pregnant on day 30 to verify the embryonic loss. The statistical analyses were performed using the SPSS for Windows. Pregnancy rates were compared by chi-square test, other parameters by ANOVA, the means were compared by Tukey test. The pregnancy rates of FTAI were 60.98% (25/41), 45% (18/40) and 40.58% (56/138) to eCG, hCG and Control, respectively, without statistic difference (P = 0.07). Even using 8 differentsires in the inseminations, the pregnancy rates were similar (P = 0.76). The size of the ovulatory follicle on the day of the FTAI didn't differ among the groups (P = 0.12). The ovulatory rate was 82%. The mean±SEM follicle diameter found on D7 didn't differ (P = 0.21), but the evaluation on D12, the diameters were 8.6 ± 4.73 (eCG), 2 ± 6.85 (hCG); 3.74 ± 4.7 mm (Control) and differed among the groups (P < 0.01). The CL area (cm²) on D7 was similar for the groups (P = 0.21), on D12 the areas were 3.05 ± 1.22; 3.97 ± 1.82; 2.65 ± 1.22 to eCG, hCG and Control group respectively (P = 0.014). It was observed the presence of a CL with area higher than 2 cm² in 80.8% of the cows of the groups eCG and hCG, meanwhile the Control group had only 54.2%. The control group had the lowest CL growth rate, 0.23 ± 0.52 cm²/day, the eCG treated had intermediary growth, 1.01 ± 1.17 cm²/day and the ones that received hCG had the highest daily growth (1.32 ± 1.63 cm²/day). Discussion: Although 20 percentage points above in the cows treated with eCG in comparison to the Control group, the pregnancy rates were statistically similar. Results indicate that treating cows with hCG 7 days after the FTAI promotes improved size of CL, induced ovulation of follicles between days 7 and 12 after FTAI causing the development of accessory CL, and the use of eCG stimulates growth of CL and follicles.

Biblioteca responsável: BR68.1