RESUMO

Objetivou-se com o presente trabalho avaliar o efeito da sazonalidade na temperatura retal (TR) e na taxa de concepção de vacas leiteiras mantidas em confinamento, bem como o efeito da temperatura retal (TR) sobre a taxa de concepção. Foram analisadas 333 inseminações de vacas em lactação, pertencentes a uma fazenda comercial localizada em Itaúna, MG. Os dados foram coletados de janeiro de 2008 a dezembro de 2009, considerando a data do parto, a temperatura retal no momento da inseminação artificial (IA) e o diagnóstico de gestação. O diagnóstico de gestação foi realizado 40 dias após a IA. O efeito da estação do ano na TR no momento da IA foi avaliado por análise de variância. Os efeitos da classe de TR (abaixo ou acima da média) no momento da IA e da estação do ano da IA na taxa de concepção foram analisados por regressão logística. A mé- dia de TR das vacas foi de 38,66°C. Vacas com TR acima de 38,66°C apresentaram menor taxa de concepção (32,52 vs 43,31%, P<0,05) do que as vacas com TR abaixo de 38,66°C. Não foi detectado efeito da sazonalidade sobre TR, mas houve tendência (P=0,09) da sazonalidade afetar a taxa de concepção (outono-inverno=39,91% vs. primavera-verão=30,83%). Vacas da raça Jersey com temperatura retal elevada apresentam menor taxa de concepçã.

The objective of the present study was to evaluate the effect of seasonality on the rectal temperature (RT) and conception rate (CR) of dairy cows kept in confinement, as well as the effect of rectal temperature (RT) on conception rate (CR). Three hundred thirty-three lactating cows, from a commercial farm located in Itaúna, MG, were inseminated. Data were collected from January 2008 to December 2009, based on calving date, rectal temperature at the time of artificial insemination (AI) and pregnancy diagnosis. The pregnancy diagnosis was performed 40 days after AI. The effect of season at the time of AI in the RT was evaluated by variance analysis. The effects of the RT class (RT below or above average) at the time of AI and the season of AI on conception rate were analyzed by logistic regression. The RT average for cows was 38.66°C. Cows with RT above 38.66°C showed a lower conception rate (32.52 vs. 43.31%, P<0.05) than the cows with RT below 38.66°C. There was no effect of seasonality on RT, but a tendency (P=0.09) of the seasonality affecting the conception rate (fall-winter = 39.91% vs. spring-summer = 30.83%) was detected. It was concluded that Jersey cows with high rectal temperature show lower conception rate.

Assuntos

RESUMO

Objetivou-se com o presente trabalho avaliar o efeito da sazonalidade na temperatura retal (TR) e na taxa de concepção de vacas leiteiras mantidas em confinamento, bem como o efeito da temperatura retal (TR) sobre a taxa de concepção. Foram analisadas 333 inseminações de vacas em lactação, pertencentes a uma fazenda comercial localizada em Itaúna, MG. Os dados foram coletados de janeiro de 2008 a dezembro de 2009, considerando a data do parto, a temperatura retal no momento da inseminação artificial (IA) e o diagnóstico de gestação. O diagnóstico de gestação foi realizado 40 dias após a IA. O efeito da estação do ano na TR no momento da IA foi avaliado por análise de variância. Os efeitos da classe de TR (abaixo ou acima da média) no momento da IA e da estação do ano da IA na taxa de concepção foram analisados por regressão logística. A mé- dia de TR das vacas foi de 38,66°C. Vacas com TR acima de 38,66°C apresentaram menor taxa de concepção (32,52 vs 43,31%, P<0,05) do que as vacas com TR abaixo de 38,66°C. Não foi detectado efeito da sazonalidade sobre TR, mas houve tendência (P=0,09) da sazonalidade afetar a taxa de concepção (outono-inverno=39,91% vs. primavera-verão=30,83%). Vacas da raça Jersey com temperatura retal elevada apresentam menor taxa de concepçã.(AU)

The objective of the present study was to evaluate the effect of seasonality on the rectal temperature (RT) and conception rate (CR) of dairy cows kept in confinement, as well as the effect of rectal temperature (RT) on conception rate (CR). Three hundred thirty-three lactating cows, from a commercial farm located in Itaúna, MG, were inseminated. Data were collected from January 2008 to December 2009, based on calving date, rectal temperature at the time of artificial insemination (AI) and pregnancy diagnosis. The pregnancy diagnosis was performed 40 days after AI. The effect of season at the time of AI in the RT was evaluated by variance analysis. The effects of the RT class (RT below or above average) at the time of AI and the season of AI on conception rate were analyzed by logistic regression. The RT average for cows was 38.66°C. Cows with RT above 38.66°C showed a lower conception rate (32.52 vs. 43.31%, P<0.05) than the cows with RT below 38.66°C. There was no effect of seasonality on RT, but a tendency (P=0.09) of the seasonality affecting the conception rate (fall-winter = 39.91% vs. spring-summer = 30.83%) was detected. It was concluded that Jersey cows with high rectal temperature show lower conception rate.(AU)

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RESUMO

Dentre os problemas que diminuem a eficiência reprodutiva em rebanhos leiteiros a falha de detecção de estro é um dos fatores mais importantes. Objetivou-se avaliar a eficiência de um dispositivo que auxilia a detecção de estros – Estrotect® e compará-lo com a detecção visual em 58 vacas mestiças leiteiras Holandês/Gir com produção média de 18,5 kg de leite/dia/vaca. Os animais foram distribuídos em dois grupos: o grupo IATF (n= 21) foi submetido a um protocolo de inseminação artificial em tempo fixo (IATF) e 10 dias após a inseminação foi fixado o dispositivo nos animais. No grupo PG (n=37), foi administrado prostaglandina 25mg/animal/IM e imediatamente colado o adesivo. Essas vacas foram monitoradas por meio de exame ultrassonográfico num período de 28 dias para verificação do desenvolvimento do corpo lúteo. Para verificar se ocorreram alterações na eficiência do dispositivo quanto aos grupos utilizou-se a regressão logística e para comparar a eficiência do mesmo em relação à observação visual utilizou-se o teste de MCNemar. Não foi detectado efeito de grupo (P>0,05) na eficiência da detecção visual de estro ou da ferramenta auxiliar. Também não foi detectada diferença entre a eficiência da detecção visual de estro e o dispositivo (P>0,05). A ferramenta auxiliar de detecção de estro (Estrotect®) se mostrou tão eficiente quanto a detecção visual e pode ser utilizada em programas de inseminação artificial de vacas leiteiras.

Among the problems that reduce the reproductive efficiency in dairy cows the failure in estrus detection is a major factor. The objective of this study was to evaluate the efficiency of Estrotect®, a device that aids heat detection in cattle, and to compare it with visual detection in 58 crossbred Holstein/Gyr dairy cows producing 18.5Kg/milk/cow. The animals were divided into two groups: the TAI (n = 21) underwent a fixed-time artificial insemination protocol (TAI), and 10 days after insemination, the device was fixed to the cows. In the PG group (n = 37) prostaglandin (dinoprost tromethamine) 25mg/animal/IM was administered, and then the device was put in place. These cows were then monitored by ultrasound over a period of 28 days to verify the development of the corpus luteum. Logistic regression was used to find out if there were alterations in the efficiency of Estrotect® within the groups, and the McNemar test was used to compare its efficiency to that of visual observation. No group effect was detected (P> 0.05) on the efficiency of visual detection nor on that of the auxiliary device. Neither was there observed any difference between the efficiency of visual detection of estrus and that of the device (P> 0.05). The auxiliary tool for the detection of estrus, (Estrotect ®), proved to be just as effective as visual detection. Thus, it can be used as an auxiliary device in conjunction with visual observation, and also as a unique tool for the detection of estrus in order to simplify the management of large herds.

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RESUMO

Background: The need for high production has increased considerably in the dairy industry. On the other hand, a fertility decline has been observed in cows with best potential for milk production. Therefore, calving intervals of around 12 months have been sought, which leaves a very short period of time for the cows to be inseminated and to become pregnant. If the conception is delayed, the reproduction inefficiency can reduce milk production, causing economic problems. The calving-conception interval (CCI) depends on multiple factors such as voluntary waiting period, insemination technique, birth season, herd size and parity. Negative effects of stress caused by heat on the fertility of lactating dairy cows have been observed. An increase in body temperature decreased the probability of conception at 28 days as the number of postpartum days increased. It is known that cows with larger calving-conception intervals have more health problems. Also, they have a greater chance of being discarded, since long CCI result in longer periods with no milk production and, therefore, expenditures with unproductive cows. Moreover, an increase in the CCI from 90 to 300 days doubled the chance of discard or peripartum death in dairy matrix. This study aimed to analyze the effect of two variables: the calving - first IA interval and on the CCI of crossbred dairy cows: duration of previous calving interval and calving season. Materials, Methods & Results: Data were collected at a property located in the state of Goiás, Brazil, between 2009 and 2010, for a herd of 71 crossbred cows with an average production of 1,400 kg of milk per day. Cows were artificially inseminated and pregnancy diagnosis was performed monthly using ultrasonography (Mindray DP3.300® VET). The previous calving interval was evaluated in three subdivisions: 1 (300 365 days) 2 (366 500 days) 3 (above 500 days) and birth season was classified as spring-summer and autumn-winter. The calving-first IA interval and the CCI were analyzed by ANOVA in MINITAB. The effects of previous calving interval and birth season were included in the model. There was no effect of duration of either previous calving interval or calving season on the calving - first IA interval, but the birth season variable affected the CCI. Cows that calved in autumn/winter had a lower CCI when compared with calving in spring/summer (80.17 d. vs. 118.50 d). Discussion: In hot summers the conception rate is lower among cows that deliver during summer and spring when compared with those that deliver during autumn and winter [4]. Other authors have shown that conception during summer was, respectively, 25 to 30% and 36% lower than during winter. Although the length of the previous birth interval did not influence the calving-conception interval, herds with average CPI greater than 13.9 months had a 1.78 times higher risk of death than herds with average CPI smaller than 13 months. In addition, the risk of cows being discarded increased due to a decline in milk production for CCI greater than 15 months. This is particularly an issue for crossbred herds due to their low lactation persistence. The CCI was significantly influenced by the calving season and it was also influenced the CCI in Gir cows in the Northeast Brazil that had calving interval of 460 +9.4 days when they that calved in spring/summer and 430.8 +9.5 days when they calved in autumn/winter. The effect of the calving season on the service period has been explained as a result of poorer feeding conditions at certain times of the year for purebreds. Other authors contradict these results, but they investigated Nelore cows, showing the adaptation of this breed in subtropical climates.

Assuntos

RESUMO

Dentre os problemas que diminuem a eficiência reprodutiva em rebanhos leiteiros a falha de detecção de estro é um dos fatores mais importantes. Objetivou-se avaliar a eficiência de um dispositivo que auxilia a detecção de estros Estrotect® e compará-lo com a detecção visual em 58 vacas mestiças leiteiras Holandês/Gir com produção média de 18,5 kg de leite/dia/vaca. Os animais foram distribuídos em dois grupos: o grupo IATF (n= 21) foi submetido a um protocolo de inseminação artificial em tempo fixo (IATF) e 10 dias após a inseminação foi fixado o dispositivo nos animais. No grupo PG (n=37), foi administrado prostaglandina 25mg/animal/IM e imediatamente colado o adesivo. Essas vacas foram monitoradas por meio de exame ultrassonográfico num período de 28 dias para verificação do desenvolvimento do corpo lúteo. Para verificar se ocorreram alterações na eficiência do dispositivo quanto aos grupos utilizou-se a regressão logística e para comparar a eficiência do mesmo em relação à observação visual utilizou-se o teste de MCNemar. Não foi detectado efeito de grupo (P>0,05) na eficiência da detecção visual de estro ou da ferramenta auxiliar. Também não foi detectada diferença entre a eficiência da detecção visual de estro e o dispositivo (P>0,05). A ferramenta auxiliar de detecção de estro (Estrotect®) se mostrou tão eficiente quanto a detecção visual e pode ser utilizada em programas de inseminação artificial de vacas leiteiras.(AU)

Among the problems that reduce the reproductive efficiency in dairy cows the failure in estrus detection is a major factor. The objective of this study was to evaluate the efficiency of Estrotect®, a device that aids heat detection in cattle, and to compare it with visual detection in 58 crossbred Holstein/Gyr dairy cows producing 18.5Kg/milk/cow. The animals were divided into two groups: the TAI (n = 21) underwent a fixed-time artificial insemination protocol (TAI), and 10 days after insemination, the device was fixed to the cows. In the PG group (n = 37) prostaglandin (dinoprost tromethamine) 25mg/animal/IM was administered, and then the device was put in place. These cows were then monitored by ultrasound over a period of 28 days to verify the development of the corpus luteum. Logistic regression was used to find out if there were alterations in the efficiency of Estrotect® within the groups, and the McNemar test was used to compare its efficiency to that of visual observation. No group effect was detected (P> 0.05) on the efficiency of visual detection nor on that of the auxiliary device. Neither was there observed any difference between the efficiency of visual detection of estrus and that of the device (P> 0.05). The auxiliary tool for the detection of estrus, (Estrotect ®), proved to be just as effective as visual detection. Thus, it can be used as an auxiliary device in conjunction with visual observation, and also as a unique tool for the detection of estrus in order to simplify the management of large herds.(AU)

Assuntos

RESUMO

Background: Reproductive efficiency is one of the most important characteristics for beef cattle. Bos indicus cattle have longer periods of postpartum anestrus, which contributes to poorer reproductive efficiency of zebu cows when compared with that of Bos taurus , this facts are particular relevant in primiparous cows. These challenges are more important in primiparous cows in pasture management systems because the intake of nutrients during the postpartum period is not sufficient to meet requirements for growth as well as lactation. The objectives of this study were to evaluate the days postpartum at conception and the pregnancy rate at the end of a 90 days breeding season in primiparous and multiparous cows. Materials, Methods & Results: The study was conducted at the Experimental Farm of the Capim Branco, Federal University of Uberlandia, in the breeding season of 2009/2010. It was used 14 primiparous and 84 multiparous Nelore cows. The females were treated with the following protocol. On Day 0, all cows received an intravaginal device containing 1.9 g progesterone (CIDR®) and 1.0 mg, i.m. of estradiol cypionate (ECP ®). On Day 7 the cows received 12.5 mg, i.m. dinoprost tromethamine (Lutalyse®). On Day 9, the intravaginal devices were removed, and calves were temporally weaned. On Day 11 (48 h after intravaginal device withdrawal), all cows were inseminated and calves reunited with their dams immediately after insemination. All cows that returned to estrus before pregnancy diagnosis were re-inseminated 12 h after estrous detection. Pregnancy diagnosis was performed by transrectal ultrasonography 30 days after TAI, confirmed 60 days after the end of breeding season. The pregnancy rate at end of the breeding season was calculated by dividing the number of pregnant cows heifers by the number of cows used in the breeding season. [...]

Assuntos

RESUMO

Background: Reproductive efficiency is one of the most important characteristics for beef cattle. Bos indicus cattle have longer periods of postpartum anestrus, which contributes to poorer reproductive efficiency of zebu cows when compared with that of Bos taurus , this facts are particular relevant in primiparous cows. These challenges are more important in primiparous cows in pasture management systems because the intake of nutrients during the postpartum period is not sufficient to meet requirements for growth as well as lactation. The objectives of this study were to evaluate the days postpartum at conception and the pregnancy rate at the end of a 90 days breeding season in primiparous and multiparous cows. Materials, Methods & Results: The study was conducted at the Experimental Farm of the Capim Branco, Federal University of Uberlandia, in the breeding season of 2009/2010. It was used 14 primiparous and 84 multiparous Nelore cows. The females were treated with the following protocol. On Day 0, all cows received an intravaginal device containing 1.9 g progesterone (CIDR®) and 1.0 mg, i.m. of estradiol cypionate (ECP ®). On Day 7 the cows received 12.5 mg, i.m. dinoprost tromethamine (Lutalyse®). On Day 9, the intravaginal devices were removed, and calves were temporally weaned. On Day 11 (48 h after intravaginal device withdrawal), all cows were inseminated and calves reunited with their dams immediately after insemination. All cows that returned to estrus before pregnancy diagnosis were re-inseminated 12 h after estrous detection. Pregnancy diagnosis was performed by transrectal ultrasonography 30 days after TAI, confirmed 60 days after the end of breeding season. The pregnancy rate at end of the breeding season was calculated by dividing the number of pregnant cows heifers by the number of cows used in the breeding season. [...](AU)

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