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


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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Available from: Luis Zarco, Oct 05, 2015
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    • "Third, female sexual behaviour may also have influenced the response of other females to the male effect. Indeed, various studies have shown that females in estrus can stimulate other females via the female effect (Walkden-Brown et al., 1993b; Restall et al., 1995; Zarco et al., 1995; Álvarez et al., 1999). In the present study, it is possible that the first females displaying estrous behaviour and ovulatory activity as a result of the male effect may have participated in the stimulation of other does. "
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    ABSTRACT: The study was conducted on two consecutive years to determine whether ovulatory activity can be induced in anovulatory goats by exposing them to sexually active bucks for 4, 8, 12 or 16 h per day during 15 consecutive days. In experiment 1, females remained continuously in the experimental pens where they were in contact with males. One group remained isolated from males (controls) and four other groups were exposed to sexually active males for 4, 8, 12 or 16 h per day. In experiment 2, females were taken away to "resting" pens free of male odours between the periods of contact with bucks. They were allocated to 5 groups as in experiment 1. Ovulations were determined by progesterone plasma levels and transrectal ultrasonography. Pregnancy was determined by abdominal ultrasonography. In both experiments, more than 90% of females exposed to the bucks had at least one ovulation during the whole experiment whereas only 11 or 0% (experiments 1 and 2, respectively) did so in the control group (P<0.001). Furthermore, the proportion of females ovulating did not differ among groups depending on duration of contact with bucks (P>0.05). In both experiments, pregnancy rates were not affected by the daily duration of contact with males (P>0.05). To conclude, 4h of daily contact with sexually active males is sufficient to stimulate ovulatory activity in anovulatory goats and this effect is not due to the presence of olfactory cues from the males remaining in the pens.
    Hormones and Behavior 05/2010; 58(3):473-7. DOI:10.1016/j.yhbeh.2010.05.002 · 4.63 Impact Factor
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    • "In these species , there is also a " female effect " , through which the presence of estrous females induces ovulation in some of their anestrous herd mates ( Walkden - Brown et al . , 1993b ; Restall et al . , 1995 ; Zarco et al . , 1995 ; Alvarez et al . , 1999 ) . It has been proposed that the male and female effects are complementary phenomena that reinforce each other to achieve synchronized reproduction in most females in a herd ( Walkden - Brown et al . , 1993b ; Zarco et al . , 1995 ) . Thus , in wild or feral ruminants , in which males and females are separated during the non - breeding"
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    ABSTRACT: The present study was conducted to determine if the social status of Australian Cashmere goats affects their response to the male effect in terms of LH secretion, ovulation and expression of estrus. Australian Cashmere goats were kept isolated from the males during 5 months. The index of success (SI) of each goat was calculated to establish their social rank. In the first experiment, the ten most dominant and the 10 most subordinate goats were separated from the original herd and housed in two pens (5 dominant and 5 subordinate animals in each pen). An androgenized wether was then introduced into each pen. Luteinizing hormone (LH) was measured every 20 min from 2h before to 4h after introduction of the male in the goats of first pen and from 4 to 8h after male introduction in the second pen. In the second experiment, the remaining 50 goats were exposed in their original pen to two androgenized wethers. Their association index with the males (AI) was calculated for each of these 50 goats, and the intervals from exposure to the males to the onset of estrus and to ovulation were determined. During the first 4h after male introduction, the dominant goats had more LH pulses (0.65+/-0.06 compared with 0.3+/-0.09; P<0.05) and greater LH mean concentrations (1.79+/-0.14 ng/ml compared with 1.30+/-0.15 ng/ml, P=0.05) than the subordinate animals. Although not significantly different, the AI was 35% greater for high and medium ranking goats than for low ranking animals (0.031+/-0.004, 0.032+/-0.005 and 0.023+/-0.005, respectively, P>0.05). Although the number of goats ovulating in response to male exposure was similar between dominance groups (high: 100%, medium: 94% and low ranking: 92%), the high and medium dominance goats showed a greater incidence of expression of estrus than low-dominance goats (94.4%, 89.5% and 53.8%, respectively, P<0.05). It is concluded that the social rank of the Australian Cashmere goat influences their response to the male effect in terms of early LH secretion and expression of estrus.
    Animal Reproduction Science 12/2007; 102(3-4):258-66. DOI:10.1016/j.anireprosci.2006.11.002 · 1.51 Impact Factor
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    • "In addition to the 'male effect', in which sexually active males induce pulses of GnRH/LH and then ovulation in anoestrous females, there is also a 'female effect', in which oestrous females induce pulses of GnRH, LH and testosterone in males, and also a 'female–female effect' in which oestrous females improve the induction of ovulation in anoestrous herd mates (goats: Walkden-Brown et al. 1993; Restall et al. 1995; Álvarez et al. 1999; ewes: Zarco et al. 1995). These interactions are self-reinforcing and enhance the final reproductive outcome in the flock (Walkden-Brown et al. 1999). "
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    ABSTRACT: Animals live in environments that are both complex and continually changing, so they have to respond to short- and long-term variations in a wide range of factors, such as photoperiod, nutrition and sociosexual signals. Before they were domesticated, animals developed reproductive strategies that coped with these changes and often took advantage of them. The physiological processes that implement these strategies have been modified to some extent during several millennia of controlled breeding, but most persist. Thus, many genotypes still exhibit profound responses to external inputs, such as the induction of ovulation by sociosexual signals and the doubling of litter size by a change in nutrition. The complexity in these responses is now becoming clearer. For example, with sociosexual signals, we now need to consider the stimulatory effects of males on females, of females on males and of females on females. Similarly, the impact of nutrition has been extended beyond the control of puberty and the production of gametes to include phenomena such as 'fetal programming', with its potentially profound effects on the life-long performance of the animals. Fortunately, our capacity to research these phenomena has been greatly enhanced by technical improvements in hormone assays, molecular and cellular biology, and real-time ultrasound. This has brought us a better understanding of several of the environmental influences on reproduction, including: the cellular processes within ovarian follicles that mediate the effect of nutrition on ovulation rate; the neuroendocrine pathways through which nutritional inputs affect the brain centres that control appetite and reproduction; and the intracerebral pathways through which sociosexual signals (olfactory and non-olfactory) stimulate the reproductive axis. Importantly, we are now beginning to realise that, as well as considering interactions between environmental inputs and genotype, we need to take into account interactions between the environmental factors themselves, just as the animals do. We still have a long way to go for a complete understanding, but we are nevertheless in a position where we can begin to use this information to develop new management systems for our animals to improve their productivity.
    Reproduction Fertility and Development 02/2004; 16(4):491-501. DOI:10.10371/RD04035 · 2.40 Impact Factor
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