Title

La complementación alimenticia incrementa la tasa ovulatoria en las cabras sometidas al efecto macho y la baja condición corporal reduce la duración de la estación sexual

Author

MA. DE LOS ANGELES DE SANTIAGO MIRAMONTES

Contributor

JOSÉ ALBERTO DELGADILLO SÁNCHEZ (Thesis Adviser)

JOSÉ ALFREDO FLORES CABRERA (Thesis Adviser)

BENOIT MALPAUX (Thesis Adviser)

GERARDO DUARTE MORENO (Thesis Adviser)

MINERVA MUÑOZ GUTIERREZ (Thesis Adviser)

Access level

Open Access

Summary or description

"En algunas razas de cabras y ovejas originarias o adaptadas a las zonas subtropicales es característica la estacionalidad de su actividad sexual. En algunas de esas razas se ha demostrado que el fotoperiodo es el principal factor que controla el inicio y el final de la estación sexual. Sin embargo, otros factores ambientales como las relaciones socio-sexuales y la alimentación pueden modificar el ritmo de reproducción anual de las hembras. El efecto macho puede inducir la actividad sexual de las cabras anéstricas, pero el porcentaje de hembras que presentan estro es menor en las hembras subalimentadas que en las bien alimentadas. Asimismo, en las vi hembras subalimentadas, la duración de la estación sexual y la tasa ovulatoria son menores que en las bien alimentadas. El porcentaje de ciclos estrales de duración anormal es mayor en las hembras subalimentadas que en las bien alimentadas. En el norte subtropical de México, la mayoría de los caprinos son mantenidos en condiciones de pastoreo y consumen exclusivamente la flora natural disponible. En consecuencia, los animales están expuestos a variaciones drásticas de la disponibilidad de alimento, ocasionando que en la época de anestro, que coincide con la sequía, el porcentaje de cabras que manifiestan estro y ovulan al ser expuestas al efecto macho sea bajo. Adicionalmente, la proporción de hembras que paren es de solamente un 47% y su prolificidad promedio es de 1.2 cabritos. No obstante, cuando éstas hembras son expuestas a machos sexualmente activos, la proporción de cabras que presentan estro es similar (>90%) a la observada en las hembras confinadas y bien alimentadas. Sin embargo, la prolificidad de las hembras en pastoreo es menor (1.6 cabritos) que en las que son mantenidas en confinamiento (2.0 cabritos). Es posible que una menor tasa ovulatoria en las hembras subalimentadas sea la causa de esta diferencia. Por otra parte, en las cabras intactas confinadas y bien alimentadas, la estación sexual inicia en Septiembre y termina en Febrero, lo cual coincide con el patrón estacional de secreción de la Hormona Luteinizante (LH)"

"Most breeds of sheep and goats from, or adapted to, subtropical latitudes exhibit seasonal variations of their sexual activity. In some of these breeds, it has been demonstrated that photoperiod is the main factor controlling the onset and the end of the breeding season. However, in these photoperiodic breeds, other environmental cues, such as sociosexual interactions and nutrition, can modify the annual reproductive rhythm in the females. The male effect can induce the sexual activity in anoestrous goats, but the percentage of females that show an oestrous behaviour is lower in under-fed than in well-fed does. Likewise, in underfed female goats the length of the breeding season and the ovulation rate xiii are lower than in well-fed ones. The percentage of oestrous cycles of normal length is greater in well-fed than in under-fed does. In subtropical northern Mexico, most of goats usually graze on natural unimproved pasture, eating only available vegetation. As a consequence, these animals are subjected to large seasonal variations of food availability, causing that in the anoestrous season, which coincides with the dry season, a low percentage of does show oestrus and ovulation when they are submitted to the male effect. Furthermore, the percentage of does kidding is only 47% with a mean prolificacy of 1.2 goat kids. However, when these does are exposed to sexually active bucks, the percentage of goats showing oestrus is similar (90%) than that observed in confined and well-fed does. However, the prolificacy in the grazing female goats is lower (1.6 kids) compared to confined well-fed does (2.0 goat kids). Possibly this difference could be due to a lesser ovulation rate in under-fed grazing females. On the other hand, in intact confined and well-fed female goats, the breeding season begins in September and ends in February. This data coincides with the seasonal pattern of Luteinizing Hormone (LH) secretion in ovariectomized does bearing a subcutaneous implant constantly releasing l7ß-estradiol (OVX+E). The onset of the breeding season, determined by the increase in LH secretion, is simultaneous in the well-fed females and those grazing in native pasture (August). However, the xiv decrease in LH secretion, indicative of the end of the breeding season, occurs until February in the well-fed does, compared to January in the grazing ones. It is possible that the advance in the end of the breeding season might be caused by the severe reduction in food availability for animals grazing natural pasture suggesting that nutrition is an important component of the complex of environmental cues that regulate the annual timing of the onset and end of breeding season in does. Therefore, we carried out two studies to: 1) determine if 7 days of nutritional supplementation before the male effect increase the ovulation rate in female goats managed under grazing conditions and 2) compare the length of the annual breeding season, some characteristics of the oestrous cycle and ovulation rate in female goats raised in local open range conditions before the study, which resulted in low body condition, with those raised in"

Publish date

October 1, 2008

Publication type

Doctoral thesis

Publication version

Published Version

Format

application/pdf

Language

Spanish

Audience

Students

Researchers

Source repository

Repositorio Digital CID-UAAAN

Downloads

284

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