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Conducta estral, concentraciones de LH y función lútea en cabras en anestro estacional inducidas a ciclar mediante el contacto con cabras en estro

Veterinaria Mexico 01/1999;
Source: DOAJ

ABSTRACT El presente trabajo tuvo como objetivo determinar el efecto de las cabras en estro sobre la actividad ovárica de sus compañeras en anestro estacional. Se utilizaron un total de 30 cabras anéstricas divididas aleatoriamente en tres grupos. El grupo I estuvo formado por 10 cabras inducidas al estro con acetato de melengestrol (MGA) combinado con una inyección intramuscular de gonadotropina sérica de yegua gestante (PMSG); el grupo II estuvo formado por 10 cabras no tratadas y mantenidas en contacto directo con los animales del grupo I durante todo el experimento, y el grupo III, formado por 10 cabras sin tratamiento que se mantuvieron alejadas de los otros dos grupos. En todos los animales se detectaron calores diariamente y se obtuvieron muestras de sangre dos veces por semana con el propósito de determinar las concentraciones de progesterona y establecer la presencia o ausencia de ovulación. Además se tomaron muestras de sangre para la determinación de LH cada 2 h desde las 36 hasta las 72 h posteriores a la aplicación de PMSG. Se consideró que un animal tenía actividad ovárica cuando sus valores de progesterona alcanzaron1ng/ml. En el grupo I, el 100% de los animales respondieron con ovulación al tratamiento. En el grupo II el 80% de los animales ovularon en un periodo de 13 días, y en el grupo III, que actuó como testigo, 40% de los animales ovularon. Los picos preovulatorios de LH se observaron a las 54.59 y 64 6 h para los grupos I y II, respectivamente; no se observaron picos de LH en el grupo III. Las diferencias observadas entre los grupos I y II con respecto al grupo III para el porcentaje de presentación de ovulación e inducción de estros fueron significativas (P < 0.05). Se concluye que la presencia de cabras en estro es capaz de inducir el estro, picos preovulatorios de LH y ovulación sincronizada en una proporción considerable de cabras en anestro estacional, lo que indica una inducción real de actividad ovárica y no simplemente una conducta de imitación.

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    ABSTRACT: The aim of this study was to assess the influence of social rank of anestrous goats on their interval to ovulation after exposure to males. Forty-five adult females were observed before and after the introduction of males to their pen. Behavioural sampling was used in both periods to record agonistic interactions. An index of success (IS) for each goat, based on its ability to displace other individuals was then calculated and three ranking categories were designated, low, medium, and high-ranking goats. When the goats were exposed to the male, scan sampling every 5 min was used to record the position of each goat with respect to the male. An index of association (IA) with the male was then calculated for each goat. The time of ovulation was determined through progesterone concentrations in samples taken daily for 30 days after the introduction of the males. The time of conception was retrospectively calculated after kidding. Analysis of variance and Mann–Whitney tests were used to compare the intervals from the introduction of the males to ovulation and to conception between categories. Spearman correlations were used to relate the time of ovulation with the indices of suc-cess and association, as well as within each index. High and medium ranking goats ovulated before low-ranking individuals (P < 0.05). A total of 32 goats (76%) ovulated after the introduction of the males to the pen. The percentages of females ovulating in the high, medium, and low-ranking groups were 81.8% (9/11), 75% (12/16) and 73% (11/15), respectively (P > 0.05). High-ranking females conceived earlier than the other two categories (P < 0.05). The time from exposure to the male to ovulation was negatively correlated with the index of success (Rs = −0.49, P < 0.05) and with the index of association of the female with the male (Rs = −0.58, P < 0.05). A positive correlation was found between a doe's index of success and her index of association with the male (Rs = 0.64, P < 0.01). It is concluded that after the introduction of males, the high-ranking goats are the first
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    ABSTRACT: El objetivo del presente trabajo fue evaluar la inducción de la actividad ovárica en cabras anéstricas sometidas a diferentes grados de contacto con cabras inducidas al estro hormonalmente. Se utilizaron 33 cabras identificadas en anestro divididas en cuatro grupos: Grupo I (n = 8), cabras que fueron tratadas con la presencia de nueve cabras en estro inducido (bioestimuladoras); grupo II (n = 9), cabras que no recibieron ningún tratamiento y permanecieron en un corral adyacente al del grupo I, separados mediante un cerco claro; el grupo III (n = 8), cabras sin tratamiento que permanecieron en un corral adyacente al del grupo I, opuesto al del grupo II, separados mediante un cerco opaco; y el grupo IV (testigo, n = 8), cabras que se mantuvieron alejadas de los demás grupos. El grupo bioestimulador respondió al tratamiento hormonal con 66.6% de hembras con ovulación; mientras que 25% de las hembras del grupo I ovularon (P > 0.05). Los grupos II, III y IV no presentaron actividad ovárica. Los resultados obtenidos sugieren que en la inducción de cabras anéstricas mediante el efecto hembra se requiere del contacto total con las hembras en estro.
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