Avaliação do desempenho reprodutivo de vacas de corte lactantes submetidas à IATF a partir da aplicação do GnRH, da manifestação estral, da reutilização de dispositivos intravaginais e da condição corporal / Evaluation of reproductive performance of lactating beef cows subjected to FTAI from the application of Gnrh, estrus manifestation, re-use of intravaginal devices and body condition

Background: The success of fixed-time artificial insemination (FTAI) is linked to several factors that affect pregnancy rates. The use of different hormones, estrus expression and body condition score (BCS) are variables that can influence the results of the technique. The increased production of calves provides greater amount of steers to slaughter. The productive intensification of the beef cows breeding depends on factors related to reproductive technique used and the physiological conditioning of animals. The objective of this study was to evaluate the effect of the application of GnRH, estrus manifestation, re-use of progesterone intravaginal devices and BCS on pregnancy rates of cows subjected to FTAI. Materials, Methods & Results: Were analyzed the effects of GnRH injection and re-use of intravaginal device, estrus manifestation and body condition score (BCS) on reproductive performance of 222 Montana beef cows subjected to fixedtime artificial insemination (FTAI). The FTAI protocol was based on the placement of intravaginal progesterone device (1st, 2nd or 3rd use) and application of estradiol benzoate (E.B.) (2 mg) on day 0. On day 8 was applied sodium cloprostenol (500 µg), removed the intravaginal device and performed the separation of calves. On day 9 was applied E.B. (1 mg) and started the observation of estrus in the morning, afternoon and morning of day 10. On the afternoon of day 10 was realized the insemination, part of the animals showed estrus received buserelin acetate (GnRH) (100µg); the same was proceeded with the animals without estrus. After FTAI the calves returned to cows. Thus, it was formed four groups: Without-Estrus/Without-GnRH; Without-Estrus/With-GnRH; With-Estrus/Without-GnRH; With-Estrus/With-GnRH. The evaluation alone of application of GnRH (with and without) and estrus manifestation (with and without) had no effect on pregnancy rates to FTAI and pregnancy final (P > 0.05). The evaluation of the interaction between GnRH and estrus had no effect on the FTAI pregnancy (P > 0.05): cows Without-Estrus/Without-GnRH did not differ those with GnRH, 33.3% and 48.4% respectively; cows With-Estrus/Without-GnRH did not differ those with GnRH, 53.2% and 53.8% respectively. Intravaginal device 1st, 2nd and 3rd use did not influence pregnancy rates to FTAI and final pregnancy, 50.0%, 57.7%, 41.7% and 91.7%, 88.5%, 93 8% respectively (P > 0.05). The BCS influenced the pregnancy rate to FTAI and final pregnancy, animals with BCS ≥ 3.0 had a higher pregnancy rate to FTAI and animals with BCS ≥ 2.5 had a higher pregnancy to final pregnancy (P < 0.05). The BCS also influenced the estrus manifestation, animals with BCS ≥ 2.5 had higher rates of estrus (P < 0.05). The intravaginal device 1st use promoted greater estrus manifestation in relation to the 2nd and 3rd use (P < 0.05). Discussion: The pregnancy rates did not have the effect of application of GnRH. Some studies report that effect of GnRH is related to estrus phase of the cow. Although 11 percentage points above to cows with estrus, the manifestation estrus did not influence the pregnancy and also did not interact with GnRH. However, it is reported that estrus before at insemination may be conducive to conception. The intravaginal devices used did not influence the pregnancy rates, showing that it is possible re-use them. The results showed at importance of BCS to pregnancy, studies report that cows with low BCS have difficulty to pregnant at FTAI and clean-up bulls. The estrus manifestation was influenced by the BCS and the intravaginal device used.

Evaluation of reproductive performance of lactating beef cows subjected to ftai from the application of gnrh, estrus manifestation, re-use of intravaginal devices and body condition / Avaliação do desempenho reprodutivo de vacas de corte lactantes submetidas à IATF a partir da aplicação do GnRH, da manifestação estral, da reutilização de dispositivos intravaginais e da condição corporal

Background: The success of fixed-time artifi cial insemination (FTAI) is linked to several factors that affect pregnancy rates. The use of different hormones, estrus expression and body condition score (BCS) are variables that can infl uence the results of the technique. The increased production of calves provides greater amount of steers to slaughter. The productive intensifi cation of the beef cows breeding depends on factors related to reproductive technique used and the physiological conditioning of animals. The objective of this study was to evaluate the effect of the application of GnRH, estrus manifestation, re-use of progesterone intravaginal devices and BCS on pregnancy rates of cows subjected to FTAI.Materials, Methods & Results: Were analyzed the effects of GnRH injection and re-use of intravaginal device, estrus manifestation and body condition score (BCS) on reproductive performance of 222 Montana beef cows subjected to fixedtime artifi cial insemination (FTAI). The FTAI protocol was based on the placement of intravaginal progesterone device (1st, 2nd or 3rd use) and application of estradiol benzoate (E.B.) (2 mg) on day 0. On day 8 was applied sodium cloprostenol (500 µg), removed the intravaginal device and performed the separation of calves. On day 9 was applied E.B. (1 mg) and started the observation of estrus in the morning, afternoon and morning of day 10

Background: The success of fixed-time artifi cial insemination (FTAI) is linked to several factors that affect pregnancy rates. The use of different hormones, estrus expression and body condition score (BCS) are variables that can infl uence the results of the technique. The increased production of calves provides greater amount of steers to slaughter. The productive intensifi cation of the beef cows breeding depends on factors related to reproductive technique used and the physiological conditioning of animals. The objective of this study was to evaluate the effect of the application of GnRH, estrus manifestation, re-use of progesterone intravaginal devices and BCS on pregnancy rates of cows subjected to FTAI.Materials, Methods & Results: Were analyzed the effects of GnRH injection and re-use of intravaginal device, estrus manifestation and body condition score (BCS) on reproductive performance of 222 Montana beef cows subjected to fixedtime artifi cial insemination (FTAI). The FTAI protocol was based on the placement of intravaginal progesterone device (1st, 2nd or 3rd use) and application of estradiol benzoate (E.B.) (2 mg) on day 0. On day 8 was applied sodium cloprostenol (500 µg), removed the intravaginal device and performed the separation of calves. On day 9 was applied E.B. (1 mg) and started the observation of estrus in the morning, afternoon and morning of day 10

Efeitos do uso de GNRH no momento da IATF e dias pós-parto sobre a taxa de prenhez em vacas de corte com cria ao pé / Effects of the use of GnRH in the moment of fixed-time artificial insemination and postpartum days on the pregnancy of the nursing beef cows

A falha na detecção de estros e o anestro pós-parto são as principais causas da baixa fertilidade nos rebanhos bovinos. Para minimizar estes problemas uma das biotecnologias recomendadas é o emprego da Inseminação Artificial em Tempo Fixo (IATF). O trabalho avaliou o uso de GnRH no momento da IATF e o número de Dias Pós-Parto (DPP) sobre o desempenho reprodutivo. Foram utilizadas 32 vacas de corte com cria ao pé, 15 vacas formaram o grupo GnRH e 17 o grupo controle. As vacas estavam com data média de 74 DPP por ocasião da IATF.Os animais formavam um grupo homogêneo sendo manejados em iguais condições.As vacas receberam no dia “0” 2 mg de benzoato de estradiol e implante intravaginal de progesterona usado previamente (2º uso), no 6º dia foi aplicado 0,375 mg de Cloprostenol Sódico e no 8º dia, pela manhã, foram retirados os implantes, separados os bezerros e foi aplicado 0,5 mg de cipionato de estradiol. No dia 10º dia pela tarde procedeu-se a IATF. Neste momento, aleatoriamente, de cada duas vacas uma recebia 100μg de análogo sintético ao GnRH. Sete dias após a IATF os animais

The lack of estrous detection and the postpartum anestrous are the largest causes of the low fertility in the beef cattle herds. To minimize these problems one of the recommended biotechnology it is the use of the fixed-time artificial insemination (TAI). This work evaluated the use of GnRH at the moment of TAI and the postpartum days (PPD) on the reproductive performance. Data of the thirty two cows rearing calves were used. Fifty cows formed the group GnRH and 17 the group control. The PPD of the cows were in medium 74 days for occasion of TAI. The animals formed one homogeneous group being handled equally. All cows received in the day “0” 2 mg of estradiol benzoato and one intravaginal implant content progesterone of 2nd use. On the 6th day was applied 0,375 mg of sodic cloprostenol and in the 8th day, by the morning, the implants were take off and the calves were separated temporarily and were applied 0,5 mg of estradiol cipionate. On the 10th day at the afternoon TAI was done. At this time randomly, one of each two cows received 100 µg of synthetic analogue to GnRH. Seven days after TAI the animals were allocated into one field with more 35 cows and 2 clean-up bulls during 60 days. It was evaluated the effects on the GnRH application on the Pregnancy rate at TAI (PRTAI) and the pregnancy rate after clean-up bulls (PRB). The effects of the PPD were analyzed on the PRTAI and PRB. The PRTAI was of 46.7% and 35.3%, respectively for the cows of the groups GnRH and control (P>0.05). The PRB was of 53.3% and 64.7%, respectively for the cows of the group GnRH and control (P>0.05). There was not relationship by the use of GnRH with PRTAI and PRB. For analyze the PPD it was formed two groups. One group (14 cows) with average of 57 ± 18.4 PPD (PPD57) and other group (18 cows) with average of 88 ± 9.1 PPD (PPD88). In the groups PPD57 and PPD88 the PRTAI was respectively 42.9% and 38.9% (P>0.05); and the PRB was respectively 64.3% and 55.6% (P>0,05)

Efeitos do uso de GNRH no momento da IATF e dias pós-parto sobre a taxa de prenhez em vacas de corte com cria ao pé / Effects of the use of GnRH in the moment of fixed-time artificial insemination and postpartum days on the pregnancy of the nursing beef cows

A falha na detecção de estros e o anestro pós-parto são as principais causas da baixa fertilidade nos rebanhos bovinos. Para minimizar estes problemas uma das biotecnologias recomendadas é o emprego da Inseminação Artificial em Tempo Fixo (IATF). O trabalho avaliou o uso de GnRH no momento da IATF e o número de Dias Pós-Parto (DPP) sobre o desempenho reprodutivo. Foram utilizadas 32 vacas de corte com cria ao pé, 15 vacas formaram o grupo GnRH e 17 o grupo controle. As vacas estavam com data média de 74 DPP por ocasião da IATF.Os animais formavam um grupo homogêneo sendo manejados em iguais condições.As vacas receberam no dia “0” 2 mg de benzoato de estradiol e implante intravaginal de progesterona usado previamente (2º uso), no 6º dia foi aplicado 0,375 mg de Cloprostenol Sódico e no 8º dia, pela manhã, foram retirados os implantes, separados os bezerros e foi aplicado 0,5 mg de cipionato de estradiol. No dia 10º dia pela tarde procedeu-se a IATF. Neste momento, aleatoriamente, de cada duas vacas uma recebia 100μg de análogo sintético ao GnRH. Sete dias após a IATF os animais(AU)

The lack of estrous detection and the postpartum anestrous are the largest causes of the low fertility in the beef cattle herds. To minimize these problems one of the recommended biotechnology it is the use of the fixed-time artificial insemination (TAI). This work evaluated the use of GnRH at the moment of TAI and the postpartum days (PPD) on the reproductive performance. Data of the thirty two cows rearing calves were used. Fifty cows formed the group GnRH and 17 the group control. The PPD of the cows were in medium 74 days for occasion of TAI. The animals formed one homogeneous group being handled equally. All cows received in the day “0” 2 mg of estradiol benzoato and one intravaginal implant content progesterone of 2nd use. On the 6th day was applied 0,375 mg of sodic cloprostenol and in the 8th day, by the morning, the implants were take off and the calves were separated temporarily and were applied 0,5 mg of estradiol cipionate. On the 10th day at the afternoon TAI was done. At this time randomly, one of each two cows received 100 µg of synthetic analogue to GnRH. Seven days after TAI the animals were allocated into one field with more 35 cows and 2 clean-up bulls during 60 days. It was evaluated the effects on the GnRH application on the Pregnancy rate at TAI (PRTAI) and the pregnancy rate after clean-up bulls (PRB). The effects of the PPD were analyzed on the PRTAI and PRB. The PRTAI was of 46.7% and 35.3%, respectively for the cows of the groups GnRH and control (P>0.05). The PRB was of 53.3% and 64.7%, respectively for the cows of the group GnRH and control (P>0.05). There was not relationship by the use of GnRH with PRTAI and PRB. For analyze the PPD it was formed two groups. One group (14 cows) with average of 57 ± 18.4 PPD (PPD57) and other group (18 cows) with average of 88 ± 9.1 PPD (PPD88). In the groups PPD57 and PPD88 the PRTAI was respectively 42.9% and 38.9% (P>0.05); and the PRB was respectively 64.3% and 55.6% (P>0,05)(AU)

Evaluation of reproductive performance of lactating beef cows subjected to ftai from the application of gnrh, estrus manifestation, re-use of intravaginal devices and body condition / Avaliação do desempenho reprodutivo de vacas de corte lactantes submetidas à IATF a partir da aplicação do GnRH, da manifestação estral, da reutilização de dispositivos intravaginais e da condição corporal

Background: The success of fixed-time artifi cial insemination (FTAI) is linked to several factors that affect pregnancy rates. The use of different hormones, estrus expression and body condition score (BCS) are variables that can infl uence the results of the technique. The increased production of calves provides greater amount of steers to slaughter. The productive intensifi cation of the beef cows breeding depends on factors related to reproductive technique used and the physiological conditioning of animals. The objective of this study was to evaluate the effect of the application of GnRH, estrus manifestation, re-use of progesterone intravaginal devices and BCS on pregnancy rates of cows subjected to FTAI.Materials, Methods & Results: Were analyzed the effects of GnRH injection and re-use of intravaginal device, estrus manifestation and body condition score (BCS) on reproductive performance of 222 Montana beef cows subjected to fixedtime artifi cial insemination (FTAI). The FTAI protocol was based on the placement of intravaginal progesterone device (1st, 2nd or 3rd use) and application of estradiol benzoate (E.B.) (2 mg) on day 0. On day 8 was applied sodium cloprostenol (500 µg), removed the intravaginal device and performed the separation of calves. On day 9 was applied E.B. (1 mg) and started the observation of estrus in the morning, afternoon and morning of day 10

Background: The success of fixed-time artifi cial insemination (FTAI) is linked to several factors that affect pregnancy rates. The use of different hormones, estrus expression and body condition score (BCS) are variables that can infl uence the results of the technique. The increased production of calves provides greater amount of steers to slaughter. The productive intensifi cation of the beef cows breeding depends on factors related to reproductive technique used and the physiological conditioning of animals. The objective of this study was to evaluate the effect of the application of GnRH, estrus manifestation, re-use of progesterone intravaginal devices and BCS on pregnancy rates of cows subjected to FTAI.Materials, Methods & Results: Were analyzed the effects of GnRH injection and re-use of intravaginal device, estrus manifestation and body condition score (BCS) on reproductive performance of 222 Montana beef cows subjected to fixedtime artifi cial insemination (FTAI). The FTAI protocol was based on the placement of intravaginal progesterone device (1st, 2nd or 3rd use) and application of estradiol benzoate (E.B.) (2 mg) on day 0. On day 8 was applied sodium cloprostenol (500 µg), removed the intravaginal device and performed the separation of calves. On day 9 was applied E.B. (1 mg) and started the observation of estrus in the morning, afternoon and morning of day 10