Efeito de dispositivos vaginais impregnados com alta ou baixa concentração de progesterona na taxa de prenhez de novilhas submetidas à inseminação artificial em tempo fixo / Effect of low- or high-dose intravaginal progesterone-releasing devices on pregnancy rates of beef heifers submitted to fixed-time artificial insemination

O presente estudo teve como objetivo avaliar o uso de dispositivos intravaginais contendo doses altas ou baixas de progesterona (P4) na taxa de prenhez de novilhas zebuínas submetidas à inseminação artificial em tempo fixo (IATF). Novilhas Bos indicus (Nelore) receberam, no dia 0, uma injeção via intramuscular (im) de 2 mg de benzoato de estradiol (BE) e, em seguida, foram divididas aleatoriamente em três grupos. Nos grupos 1 (n = 80) e 2 (n = 79) foi colocado um dispositivo intravaginal contendo 1,9 g (grupo 1) e 0,75 g (grupo 2) de P4, enquanto que o grupo 3 (n = 76) não recebeu dispositivo. Os dispositivos intravaginais foram removidos no dia 8, juntamente com a aplicação im de uma dose luteolíticade cloprostenol. Metade dos animais de cada grupo recebeu, adicionalmente, uma injeção im de 300 UI de eCG. Vinte e quatro horas depois, todos animais receberam uma segunda aplicação im de 1 mg de BE e foram inseminados 54-56 horas após a aplicação de cloprostenol. O diagnóstico de prenhez foi realizado 40 dias após a IATF, por meio de ultrassonografia transretal. Os dados foram analisados por regressão logística. As taxas de prenhez foram de 27,5%, 30,4% e 28,9% para os grupos 1, 2 e 3, respectivamente (P>0,05). A injeção de eCG, bem como outras variáveis tais como escore corporal, fazenda e presença de CL no início dos tratamentos não influenciaram esse resultado. Em conclusão, o uso de dispositivos intravaginas contendo alto (1,9 g) ou baixo (0,75 g) teor de P4 resultou em semelhantes taxas de prenhez após IATF de novilhas Nelore púberes.

This study aimed to evaluate the use of low- or high-dose intravaginal progesterone (P4)-releasing devices on pregnancy rates of Zebu heifers submitted to fixed-timed artificial insemination (TAI). Pubertal Bos indicus Nellore heifers were injected at day 0 with 2 mg estradiol benzoate (EB) and assigned randomly to three groups. An intravaginal device containing 1.9 or 0.75 g P4 was inserted in animals of groups 1 (n=80) and 2 (n=79), while group 3 (n=76) received no device. The intravaginal devices were removed on day 8 and one luteolytic dose (125 μg) of d-cloprostenol was administered. Half of the animals in each group additionally received 300 IU of eCG. Twenty-four hours later, the heifers received a second injection of 1 mg EB and TAI was performed 54 hours after the injection of cloprostenol. Pregnancy was diagnosed 40 days after TAI by transrectal ultrasonography. Data were analyzed by logistic regression. Pregnancy rates were 27.5%, 30.4% and 28.9% in groups 1, 2 and 3, respectively (P>0.05). This result was not influenced by body score, farm, eCG, or presence of CL at the beginning of the treatments. In conclusion, the use of intravaginal devices containing either a high (1.9 g) or low (0.75 g) dose of P4 resulted in similar pregnancy rates after TAI in pubertal Nellore heifers.

Efeito de dispositivos vaginais impregnados com alta ou baixa concentração de progesterona na taxa de prenhez de novilhas submetidas à inseminação artificial em tempo fixo / Effect of low- or high-dose intravaginal progesterone-releasing devices on pregnancy rates of beef heifers submitted to fixed-time artificial insemination

O presente estudo teve como objetivo avaliar o uso de dispositivos intravaginais contendo doses altas ou baixas de progesterona (P4) na taxa de prenhez de novilhas zebuínas submetidas à inseminação artificial em tempo fixo (IATF). Novilhas Bos indicus (Nelore) receberam, no dia 0, uma injeção via intramuscular (im) de 2 mg de benzoato de estradiol (BE) e, em seguida, foram divididas aleatoriamente em três grupos. Nos grupos 1 (n = 80) e 2 (n = 79) foi colocado um dispositivo intravaginal contendo 1,9 g (grupo 1) e 0,75 g (grupo 2) de P4, enquanto que o grupo 3 (n = 76) não recebeu dispositivo. Os dispositivos intravaginais foram removidos no dia 8, juntamente com a aplicação im de uma dose luteolíticade cloprostenol. Metade dos animais de cada grupo recebeu, adicionalmente, uma injeção im de 300 UI de eCG. Vinte e quatro horas depois, todos animais receberam uma segunda aplicação im de 1 mg de BE e foram inseminados 54-56 horas após a aplicação de cloprostenol. O diagnóstico de prenhez foi realizado 40 dias após a IATF, por meio de ultrassonografia transretal. Os dados foram analisados por regressão logística. As taxas de prenhez foram de 27,5%, 30,4% e 28,9% para os grupos 1, 2 e 3, respectivamente (P>0,05). A injeção de eCG, bem como outras variáveis tais como escore corporal, fazenda e presença de CL no início dos tratamentos não influenciaram esse resultado. Em conclusão, o uso de dispositivos intravaginas contendo alto (1,9 g) ou baixo (0,75 g) teor de P4 resultou em semelhantes taxas de prenhez após IATF de novilhas Nelore púberes.(AU)

This study aimed to evaluate the use of low- or high-dose intravaginal progesterone (P4)-releasing devices on pregnancy rates of Zebu heifers submitted to fixed-timed artificial insemination (TAI). Pubertal Bos indicus Nellore heifers were injected at day 0 with 2 mg estradiol benzoate (EB) and assigned randomly to three groups. An intravaginal device containing 1.9 or 0.75 g P4 was inserted in animals of groups 1 (n=80) and 2 (n=79), while group 3 (n=76) received no device. The intravaginal devices were removed on day 8 and one luteolytic dose (125 μg) of d-cloprostenol was administered. Half of the animals in each group additionally received 300 IU of eCG. Twenty-four hours later, the heifers received a second injection of 1 mg EB and TAI was performed 54 hours after the injection of cloprostenol. Pregnancy was diagnosed 40 days after TAI by transrectal ultrasonography. Data were analyzed by logistic regression. Pregnancy rates were 27.5%, 30.4% and 28.9% in groups 1, 2 and 3, respectively (P>0.05). This result was not influenced by body score, farm, eCG, or presence of CL at the beginning of the treatments. In conclusion, the use of intravaginal devices containing either a high (1.9 g) or low (0.75 g) dose of P4 resulted in similar pregnancy rates after TAI in pubertal Nellore heifers.(AU)

Effect of cold stress on physicochemical characteristics and biological activity of equine chorionic gonadotropin

The purpose of this study was to evaluate iffreezing-thawing and cooling processes affect thestructural properties and biological activity ofcommercial equine chorionic gonadotropin (eCG). First,the structure profile of diluted eCG underwent none,one or three cycles of freezing-thawing was analysed byreverse phase high-performance liquid chromatography(RP-HPLC). In a second experiment, groups ofprepuberal rats were treated with sterile water forinjection USP or eCG that underwent none, one or threecycles of freezing-thawing to assess the increase ofovarian weigh. Finally, groups of prepubertal gilts weretreated with diluted eCG immediately afterreconstitution (T1), after refrigeration for six months(T2) and after freezing and subsequently thawing for one(T3) or three (T4) cycles. The control group (T5) receivedsterile water for injection USP without eCG. Ovulationwas induced with human chorionic gonadotropin (hCG),administered 72 h after the eCG. Gilts were slaughteredfive days after the hCG injection and ovaries wererecovered and analysed for the presence of corporalutea. Data were analysed by ANOVA and Fisher’sexact tests. In the analyses by RP-HPLC, the retentiontimes of cold stressed eCG were similar to unstressedcontrol. The mean ovarian weight of rats treated with coldstressed and unstressed eCG was statistically higher thanwater control (P < 0.05). Lastly, significantly more giltsovulated in groups T1, T2, T3 and T4 than in thecontrol T5 (P < 0.05). It was concluded that freezingthawing,as well as cooling over a period of up to sixmonths, did not significantly change the structuralproperties or biological activity of eCG.

Effect of cold stress on physicochemical characteristics and biological activity of equine chorionic gonadotropin

The purpose of this study was to evaluate iffreezing-thawing and cooling processes affect thestructural properties and biological activity ofcommercial equine chorionic gonadotropin (eCG). First,the structure profile of diluted eCG underwent none,one or three cycles of freezing-thawing was analysed byreverse phase high-performance liquid chromatography(RP-HPLC). In a second experiment, groups ofprepuberal rats were treated with sterile water forinjection USP or eCG that underwent none, one or threecycles of freezing-thawing to assess the increase ofovarian weigh. Finally, groups of prepubertal gilts weretreated with diluted eCG immediately afterreconstitution (T1), after refrigeration for six months(T2) and after freezing and subsequently thawing for one(T3) or three (T4) cycles. The control group (T5) receivedsterile water for injection USP without eCG. Ovulationwas induced with human chorionic gonadotropin (hCG),administered 72 h after the eCG. Gilts were slaughteredfive days after the hCG injection and ovaries wererecovered and analysed for the presence of corporalutea. Data were analysed by ANOVA and Fishersexact tests. In the analyses by RP-HPLC, the retentiontimes of cold stressed eCG were similar to unstressedcontrol. The mean ovarian weight of rats treated with coldstressed and unstressed eCG was statistically higher thanwater control (P < 0.05). Lastly, significantly more giltsovulated in groups T1, T2, T3 and T4 than in thecontrol T5 (P < 0.05). It was concluded that freezingthawing,as well as cooling over a period of up to sixmonths, did not significantly change the structuralproperties or biological activity of eCG.(AU)

Indução da ovulação e características ovarianas de marrãs pré-púberes tratadas com gonadotrofina coriônica humana ou kisspeptina / Induction of ovulation and ovarian characteristics of prepubertal gilts treated with human chorionicgonadotropin or kisspeptin

Devido à semelhança na estrutura e função com o hormônio luteinizante (LH), a gonadotrofina coriônica humana (hCG) tem sido convencionalmente o principal hormônio utilizado para induzir o estro e a ovulação nas fêmeas suínas. Recentemente, foi demonstrado que o neuropeptídio kisspeptina é o precursor da descarga de LH em diferentes espécies de mamíferos, incluindo a suína. Dessa forma, o presente estudo objetivou determinar se uma das formas dessa substância (kisspeptina-10) associada à gonadotrofina coriônica equina (eCG) pode ser um método eficiente para induzir a ovulação de marrãs pré-púberes. Trinta marrãs de 5 meses de idade, com peso médio de 78,0 ± 8,4 kg, foram distribuídas aleatoriamente em cinco grupos de seis animais cada. Os grupos 1, 2 e 3 receberam 750 UI de eCG, enquanto que os grupos 4 e 5 receberam solução fisiológica. Setenta e duas horas após, o grupo 2 recebeu 380 nmol de kisspeptina-10, os grupos 3 e 4 receberam 500 UI de hCG e os grupo 1 e 5 receberam solução fisiológica. As injeções foram aplicadas em dose única, utilizando a via intramuscular. Os animais foram abatidos sete dias após e a ovulação foi constatada pela presença de corpos lúteos nos ovários recuperados. Os dados foram analisados pelo teste de Kruscal-Wallis e teste exato de Fisher. O número de fêmeas que ovulou foi semelhante nos grupos 2 e 3. Essa resposta foi superior ao grupo 5 (P<0,01) e aos grupos 1 e 4 (P=0,08). O peso e o tamanho dos ovários não foram influenciados pelos tratamentos, enquanto que o número de ovulações foi maior para os grupos 2 e 3 (P<0,01). Esses resultados sugerem que a kisspeptina-10 tem atividade biológica comparável à hCG para induzir a ovulação de marrãs pré-púberes...

In view of its similar structure and function to luteinizing hormone (LH), human chorionic gonadotropin (hCG) has conventionally been used as the main hormone to induce estrus and ovulation in sows. Recently, it has been demonstrated that the neuropeptide kisspeptin is associated with pituitary LH release in different mammalian species, including swine. Thus, the aim of this study was to determine whether kisspeptin-10 combined with equine chorionic gonadotropin (eCG) could be an efficient method to induce ovulation in prepubertal gilts. Thirty 5-month-old gilts weighing 78.0 ± 8.4 kg were randomly divided into five groups of six animals each. Groups 1, 2 and 3 received 750 IU eCG, while groups 4 and 5 received saline solution. After 72 hours, the animals received 380 nmol kisspeptin-10 (group 2), 500 IU hCG (groups 3 and 4), or saline (groups 1 and 5). The treatments were applied by a single intramuscular injection. The animals were slaughtered 7 days later and ovulation was confirmed by the presence of corpora lutea in the recovered ovaries. Data were analyzed by the Kruskal-Wallis and Fisher exact tests. The number of gilts that ovulated was similar in groups 2 and 3. This number was higher in group 5 (P<0.01) and in groups 1 and 4 (P=0.08). The weight or size of the ovaries was not influenced by the treatments, although the number of ovulations was higher in groups 2 and 3 (P<0.01). These results suggest that kisspeptin-10 and hCG have similar biological activity to induce ovulation in prepubertal gilts...

Indução da ovulação e características ovarianas de marrãs pré-púberes tratadas com gonadotrofina coriônica humana ou kisspeptina / Induction of ovulation and ovarian characteristics of prepubertal gilts treated with human chorionicgonadotropin or kisspeptin

Devido à semelhança na estrutura e função com o hormônio luteinizante (LH), a gonadotrofina coriônica humana (hCG) tem sido convencionalmente o principal hormônio utilizado para induzir o estro e a ovulação nas fêmeas suínas. Recentemente, foi demonstrado que o neuropeptídio kisspeptina é o precursor da descarga de LH em diferentes espécies de mamíferos, incluindo a suína. Dessa forma, o presente estudo objetivou determinar se uma das formas dessa substância (kisspeptina-10) associada à gonadotrofina coriônica equina (eCG) pode ser um método eficiente para induzir a ovulação de marrãs pré-púberes. Trinta marrãs de 5 meses de idade, com peso médio de 78,0 ± 8,4 kg, foram distribuídas aleatoriamente em cinco grupos de seis animais cada. Os grupos 1, 2 e 3 receberam 750 UI de eCG, enquanto que os grupos 4 e 5 receberam solução fisiológica. Setenta e duas horas após, o grupo 2 recebeu 380 nmol de kisspeptina-10, os grupos 3 e 4 receberam 500 UI de hCG e os grupo 1 e 5 receberam solução fisiológica. As injeções foram aplicadas em dose única, utilizando a via intramuscular. Os animais foram abatidos sete dias após e a ovulação foi constatada pela presença de corpos lúteos nos ovários recuperados. Os dados foram analisados pelo teste de Kruscal-Wallis e teste exato de Fisher. O número de fêmeas que ovulou foi semelhante nos grupos 2 e 3. Essa resposta foi superior ao grupo 5 (P<0,01) e aos grupos 1 e 4 (P=0,08). O peso e o tamanho dos ovários não foram influenciados pelos tratamentos, enquanto que o número de ovulações foi maior para os grupos 2 e 3 (P<0,01). Esses resultados sugerem que a kisspeptina-10 tem atividade biológica comparável à hCG para induzir a ovulação de marrãs pré-púberes...(AU)

In view of its similar structure and function to luteinizing hormone (LH), human chorionic gonadotropin (hCG) has conventionally been used as the main hormone to induce estrus and ovulation in sows. Recently, it has been demonstrated that the neuropeptide kisspeptin is associated with pituitary LH release in different mammalian species, including swine. Thus, the aim of this study was to determine whether kisspeptin-10 combined with equine chorionic gonadotropin (eCG) could be an efficient method to induce ovulation in prepubertal gilts. Thirty 5-month-old gilts weighing 78.0 ± 8.4 kg were randomly divided into five groups of six animals each. Groups 1, 2 and 3 received 750 IU eCG, while groups 4 and 5 received saline solution. After 72 hours, the animals received 380 nmol kisspeptin-10 (group 2), 500 IU hCG (groups 3 and 4), or saline (groups 1 and 5). The treatments were applied by a single intramuscular injection. The animals were slaughtered 7 days later and ovulation was confirmed by the presence of corpora lutea in the recovered ovaries. Data were analyzed by the Kruskal-Wallis and Fisher exact tests. The number of gilts that ovulated was similar in groups 2 and 3. This number was higher in group 5 (P<0.01) and in groups 1 and 4 (P=0.08). The weight or size of the ovaries was not influenced by the treatments, although the number of ovulations was higher in groups 2 and 3 (P<0.01). These results suggest that kisspeptin-10 and hCG have similar biological activity to induce ovulation in prepubertal gilts...(AU)