Influence of follicular growth stimulation on fertility of beef cows treated with eCG or FSH in FTAI protocols / Influência da estimulação do crescimento folicular na fertilidade de vacas de corte tratadas com eCG ou FSH em protocolos de IATF

Background: The pregnancy rate in fixed-time insemination (FTAI) programs in beef cattle is affected by several factors, including the size of ovulatory follicle (OF). Induced ovulation of small OF (≤11 mm) reduces the chance of pregnancy after FTAI when compared to ovulation of larger follicles (≥12 mm). Hormonal treatments to enhance the follicle growth have been widely used in comercial beef cattle systems, aiming to improve the development of a dominant follicle. The objective of this experiment was to evaluate the effect of treatment with eCG or FSH at the time of progesterone implant removal on the diameter of OF, final follicle growth and pregnancy rate in beef cows.Materials, Methods & Results: Three hundred and seven suckled beef cows with body condition score 2.80 ± 0.24 (1 to 5 scale) and 45 to 70 days postpartum were synchronized to FTAI. On day 0, intravaginal implants containing 1 g of progesterone, were inserted and administered 2 mg of estradiol benzoate (EB), i.m. On day 7, intravaginal implants were removed and 150 µg of D-cloprostenol were administered i.m. At this time, three groups were assigned according to the treatments: eCG (400 UI eCG, i.m.), FSH (25 UI FSH, i.m.) and Control (1 mL Saline, i.m.). On day 8, all cows were injected with 1mg EB i.m. and were inseminated 52 to 56 h after the implant removal. Transrectal ultrasonography exams of ovaries were performed at the time of implant removal and before FTAI to determine the diameter of the largest follicle and the follicular daily growth. Pregnancy exams were conducted by transretal ultrasonography 30 days after FTAI. Statistical analyzes were performed by Chi-square test for pregnancy rate. Ovarian diameters and follicular daily growth were analyzed by ANOVA with means compared by Tukey test considering significant P value < 0.05.[...]

Influence of follicular growth stimulation on fertility of beef cows treated with eCG or FSH in FTAI protocols / Influência da estimulação do crescimento folicular na fertilidade de vacas de corte tratadas com eCG ou FSH em protocolos de IATF

Background: The pregnancy rate in fixed-time insemination (FTAI) programs in beef cattle is affected by several factors, including the size of ovulatory follicle (OF). Induced ovulation of small OF (≤11 mm) reduces the chance of pregnancy after FTAI when compared to ovulation of larger follicles (≥12 mm). Hormonal treatments to enhance the follicle growth have been widely used in comercial beef cattle systems, aiming to improve the development of a dominant follicle. The objective of this experiment was to evaluate the effect of treatment with eCG or FSH at the time of progesterone implant removal on the diameter of OF, final follicle growth and pregnancy rate in beef cows.Materials, Methods & Results: Three hundred and seven suckled beef cows with body condition score 2.80 ± 0.24 (1 to 5 scale) and 45 to 70 days postpartum were synchronized to FTAI. On day 0, intravaginal implants containing 1 g of progesterone, were inserted and administered 2 mg of estradiol benzoate (EB), i.m. On day 7, intravaginal implants were removed and 150 µg of D-cloprostenol were administered i.m. At this time, three groups were assigned according to the treatments: eCG (400 UI eCG, i.m.), FSH (25 UI FSH, i.m.) and Control (1 mL Saline, i.m.). On day 8, all cows were injected with 1mg EB i.m. and were inseminated 52 to 56 h after the implant removal. Transrectal ultrasonography exams of ovaries were performed at the time of implant removal and before FTAI to determine the diameter of the largest follicle and the follicular daily growth. Pregnancy exams were conducted by transretal ultrasonography 30 days after FTAI. Statistical analyzes were performed by Chi-square test for pregnancy rate. Ovarian diameters and follicular daily growth were analyzed by ANOVA with means compared by Tukey test considering significant P value < 0.05.[...](AU)

Administration of human chorionic gonadotropin to improve luteal function in lactating beef cattle / Administração de gonadotrofina coriônica humana para estimulação da função luteal em vacas de corte lactantes

Background: Pregnancy rate after fixed-time artificial insemination (FTAI) in beef cattle is affected by ovulation rate,luteal function and embryo survival. Cows in early post partum period frequently have low progesterone productionand short luteal phases. Treatments using human chorionic gonadotropin (hCG) after FTAI have been tested in aneffort to increase progesterone concentration, improve embryo development and consequently pregnancy rates. Theobjectives of this work were to evaluate the effects of administration of hCG on day 4 after FTAI on induction ofovulation of the first dominant follicle, corpus luteum (CL) development, progesterone production and pregnancyrate in lactating beef cows.Materials, Methods & Results: Five hundred and sixty nine multiparous Angus suckled beef cows, 45-70 dayspostpartum, were synchronized to FTAI. On day -9, intravaginal implants containing 0,750 g of progesterone wereinserted and 2mg of estradiol benzoate administered, im. Seven days later, cows had their implants removed andwere injected with 150 µg of d-cloprostenol, im, and 1 mg of estradiol cipionate, im. Cows were inseminated 52-56h after implant removal. Four days later, cows were assigned into two groups, hCG (1500 UI of hCG, im, n = 269) orControl (1,5 mL saline, im, n = 300). Blood samples were collected on days 4, 7, 10 and 14 after FTAI for analysisof serum progesterone concentration by radioimmunoassay. Ovarian ultrasonographic exams were done on day 0 todetermine the diameter of ovulatory follicle (OF), on day 4 to measure the diameter of the first dominant follicle and,on day 7, to determine the CL area (cm2) and the number of accesory CL. Pregnancy diagnosis were done on day 30.Pregnancy rates were compared by chi-square test, progesterone concentration and CLs parameters were comparedby student-t test. The administration of hCG resulted in higher serum progesterone concentration, improved CL areaand the frequency of accessory CL...

Administration of human chorionic gonadotropin to improve luteal function in lactating beef cattle / Administração de gonadotrofina coriônica humana para estimulação da função luteal em vacas de corte lactantes

Background: Pregnancy rate after fixed-time artificial insemination (FTAI) in beef cattle is affected by ovulation rate,luteal function and embryo survival. Cows in early post partum period frequently have low progesterone productionand short luteal phases. Treatments using human chorionic gonadotropin (hCG) after FTAI have been tested in aneffort to increase progesterone concentration, improve embryo development and consequently pregnancy rates. Theobjectives of this work were to evaluate the effects of administration of hCG on day 4 after FTAI on induction ofovulation of the first dominant follicle, corpus luteum (CL) development, progesterone production and pregnancyrate in lactating beef cows.Materials, Methods & Results: Five hundred and sixty nine multiparous Angus suckled beef cows, 45-70 dayspostpartum, were synchronized to FTAI. On day -9, intravaginal implants containing 0,750 g of progesterone wereinserted and 2mg of estradiol benzoate administered, im. Seven days later, cows had their implants removed andwere injected with 150 µg of d-cloprostenol, im, and 1 mg of estradiol cipionate, im. Cows were inseminated 52-56h after implant removal. Four days later, cows were assigned into two groups, hCG (1500 UI of hCG, im, n = 269) orControl (1,5 mL saline, im, n = 300). Blood samples were collected on days 4, 7, 10 and 14 after FTAI for analysisof serum progesterone concentration by radioimmunoassay. Ovarian ultrasonographic exams were done on day 0 todetermine the diameter of ovulatory follicle (OF), on day 4 to measure the diameter of the first dominant follicle and,on day 7, to determine the CL area (cm2) and the number of accesory CL. Pregnancy diagnosis were done on day 30.Pregnancy rates were compared by chi-square test, progesterone concentration and CLs parameters were comparedby student-t test. The administration of hCG resulted in higher serum progesterone concentration, improved CL areaand the frequency of accessory CL...(AU)

Efeito da aplicação de eCG ou hCG 7 dias após a IATF no desenvolvimento das estruturas ovarianas e nas taxas de prenhez de vacas de corte / Effect of administration of eCG or hCG 7 days after FTAI on the development of ovarian structures and pregnancy rates in beef cows

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.