Plasma PGFM and progesterone concentrations, luteolysis moment and estrous cycle length in Nelore cows submitted to uterine biopsies / Concentrações plasmáticas de PGFM e progesterona, luteólise e comprimento do ciclo estral em vacas Nelore submetidas à coleta de fragmentos endometriais

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.(AU)

No presente estudo, foram coletadas amostras endometriais de 14 vacas Nelore nos dias zero (dia da ovulação), cinco, nove, 13 e 19 do ciclo estral (grupo controle), e em 15 fêmeas essas coletas não foram realizadas (grupo controle). As biópsias foram realizadas no corno uterino contralateral ao ovário contendo o corpo lúteo. Amostras plasmáticas foram coletadas nos momentos -24, -16, -8, 0 +8, +16 e +24 horas em relação à queda de progesterona (<1ng/mL, momento zero) e avaliadas quanto à concentração de 13, 14-di-hidro-15-ceto prostaglandina F2-alpha (PGFM) por radioimunoensaio (RIA). As concentrações plasmáticas de progesterona foram avaliadas a cada 24 horas também por RIA. Os dados foram analisados por ANOVA empregando-se PROC GLM e MIXED do SAS. O valor médio de PGFM durante todo o período avaliado foi maior no grupo biópsia. A concentração média de PGFM no momento zero não diferiu entre os grupos, e foi maior no grupo biópsia antes e após a queda de progesterona. A concentração máxima observada não foi diferente entre os grupos, porém a concentração mínima diferiu com maiores valores observados no grupo biópsia. Embora as concentrações de PGFM fossem maior no grupo biópsia, ambos os grupos apresentaram o mesmo comprimento do ciclo estral, demonstrando que a coleta repetitiva de biópsias endometriais no corno uterino contraletral ao ovário contendo o corpo lúteo não afeta a luteólise e o comprimento do ciclo estral.(AU)

Follicular growth and plasma progesterone patterns in Bos indicus x Bos taurus heifers submitted to different PGF2/progesterone-based synchronization protocols

The effect of different levels of progesterone (P4) concentrations on follicle growth and ovulatory capacity was evaluated in 40 crossbred Bos indicus x Bos taurus cyclic heifers submitted to distinct PGF2α + progesterone-based protocols. Heifers in CIDR_PGF8 group (n = 10) received 2.0 mg i.m. estradiol benzoate (EB) and a new controlled internal drug release containing 1.9 g of progesterone (CIDR) on day 0 of study. At the time of CIDR withdrawal (day 8), heifers received an i.m. injection of PGF2α and 24 h later a second EB i.m. injection (0.5 mg). The three other groups received EB injections and CIDR insertion/withdrawal as aforementioned, except that an i.m. injection of PGF2α was administered on day 5. In addition, heifers in the CIDR_PGF5 group (n = 10) received a new CIDR, while heifers in theCIDR1x_PGF5 (n = 9) and CIDR2x_PGF5 (n = 11) groups received a previously used CIDR for 8 and 14 days, respectively. Heifers that received a PGF2α injection on day 5 showed lower circulating P4 than heifers treated on day 8 (CIDR_PGF5 = 1.98 ± 0.21 ng/ml; CIDR1x_PGF5 = 1.69 ± 0.17 ng/ml and CIDR2x_PGF5 = 1.33 ± 0.08 ng/ml versus CIDR_PGF8 = 3.31 ± 0.45 ng/ml). The dominant follicle (DF) growth rate was slower in those heifers receiving PGF2α injection on day 8 (CIDR_PGF8 = 0.72 ± 0.13 mm/day) than groups treated on day 5 (CIDR_PGF5 = 0.96 ± 0.12 mm/day; CIDR1x_PGF5 = 1.06 ± 0.15 mm/day and CIDR2x_PGF5 = 1.01 ± 0.06mm/day). In consequence, preovulatory follicle diameter on day 10 was smaller in those animals injected on day 8 (CIDR_PGF8 = 8.81 ± 6.7 mm) than in those treated on day 5 (CIDR_PGF5 = 10.00 ± 0.58 mm CIDR1x_PGF5 = 10.5 ± 0.69 mm and CIDR2x_PGF5 = 10.5 ± 0.35 mm). For heifers receiving PGF2α injection on day 5, no significant differences on plasma P4 concentrations, folliculargrowth rate and DF diameters were observed among heifers that received new or previously used CIDR inserts. These results suggest that the presence of corpus luteum during synchronization protocols is the main factor responsible for the increase in the plasma P4 concentrations and inhibition of DF growth.(AU)

Follicular growth and plasma progesterone patterns in Bos indicus x Bos taurus heifers submitted to different PGF2/progesterone-based synchronization protocols

The effect of different levels of progesterone (P4) concentrations on follicle growth and ovulatory capacity was evaluated in 40 crossbred Bos indicus x Bos taurus cyclic heifers submitted to distinct PGF2α + progesterone-based protocols. Heifers in CIDR_PGF8 group (n = 10) received 2.0 mg i.m. estradiol benzoate (EB) and a new controlled internal drug release containing 1.9 g of progesterone (CIDR) on day 0 of study. At the time of CIDR withdrawal (day 8), heifers received an i.m. injection of PGF2α and 24 h later a second EB i.m. injection (0.5 mg). The three other groups received EB injections and CIDR insertion/withdrawal as aforementioned, except that an i.m. injection of PGF2α was administered on day 5. In addition, heifers in the CIDR_PGF5 group (n = 10) received a new CIDR, while heifers in theCIDR1x_PGF5 (n = 9) and CIDR2x_PGF5 (n = 11) groups received a previously used CIDR for 8 and 14 days, respectively. Heifers that received a PGF2α injection on day 5 showed lower circulating P4 than heifers treated on day 8 (CIDR_PGF5 = 1.98 ± 0.21 ng/ml; CIDR1x_PGF5 = 1.69 ± 0.17 ng/ml and CIDR2x_PGF5 = 1.33 ± 0.08 ng/ml versus CIDR_PGF8 = 3.31 ± 0.45 ng/ml). The dominant follicle (DF) growth rate was slower in those heifers receiving PGF2α injection on day 8 (CIDR_PGF8 = 0.72 ± 0.13 mm/day) than groups treated on day 5 (CIDR_PGF5 = 0.96 ± 0.12 mm/day; CIDR1x_PGF5 = 1.06 ± 0.15 mm/day and CIDR2x_PGF5 = 1.01 ± 0.06mm/day). In consequence, preovulatory follicle diameter on day 10 was smaller in those animals injected on day 8 (CIDR_PGF8 = 8.81 ± 6.7 mm) than in those treated on day 5 (CIDR_PGF5 = 10.00 ± 0.58 mm CIDR1x_PGF5 = 10.5 ± 0.69 mm and CIDR2x_PGF5 = 10.5 ± 0.35 mm). For heifers receiving PGF2α injection on day 5, no significant differences on plasma P4 concentrations, folliculargrowth rate and DF diameters were observed among heifers that received new or previously used CIDR inserts. These results suggest that the presence of corpus luteum during synchronization protocols is the main factor responsible for the increase in the plasma P4 concentrations and inhibition of DF growth.