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Los machos cabríos fotoestimulados mantienen elevada la LH en las hembras caprinas durante el anestro estacional, y los machos cabríos familiares (conocidos) inducen la ovulación en las cabras anéstricas

ALFONSO LONGINOS MUÑOZ BENITEZ (2016)

"En cabras, la presencia permanente de machos convertidos sexualmente activos mediante tratamientos fotoperiódicos, previene la aparición de anovulación estacional y la introducción de estos machos sexualmente activos inducen ovulaciones durante el anestro estacional. Usamos cabras ovariectomizadas con implantes subcutáneos rellenos o no con estradiol para determinar 1) si la presencia permanente de machos sexualmente activos previene la disminución de LH durante el anestro estacional, y 2) si la introducción de machos fotoestimulados aumenta las concentraciones plasmáticas de LH durante el anestro estacional En el Experimento 1, utilizamos cabras ovariectomizadas con implantes subcutáneos de 12 mm que contienen estradiol (OVX + E2). Un grupo de cabras (n = 13) permaneció en contacto permanente con dólares naturalmente activados (noviembre-enero) o estimulados sexualmente (febrero-mayo); el otro grupo (n = 13) permaneció en contacto permanente con palos de control que mostraron un comportamiento sexual intenso (noviembre de enero) o débil (febrero-mayo). Las concentraciones plasmáticas de LH fueron altas y no difirieron entre los grupos de noviembre a enero (P> 0.05), cuando el control mostró un comportamiento sexual intenso. Posteriormente, las concentraciones de LH disminuyeron desde marzo (P <0.05), y permanecieron bajas hasta mayo, cuando los machos de control mostraron un comportamiento sexual débil. Por el contrario, las concentraciones de LH no disminuyeron y permanecieron altas de marzo a mayo en cabras en contacto con los dólares fotoestimulados (P> 0.05). En el Experimento 2, dos grupos de mujeres (n = 6 cada una) que llevaban implantes subcutáneos vacíos de 12 mm estuvieron expuestos, durante el anestro estacional, a los baches controlados o fotoestimulados; otros dos grupos (n = 6 cada uno) que llevaban implantes subcutáneos de 12 mm llenos de estradiol, también estuvieron expuestos al control o a los baches fotoestimulados. Las concentraciones plasmáticas de LH no aumentaron en cabras con implantes vacíos, cuando se las expuso al control (de 2,01 ± 0,26 a 1,98 ± 0,31 ng / ml) o de bazos fotoestimuladas (de 2,45 ± 0,29 a 2,42 ± 0,21 ng / ml; P> 0,05). En contraste, las concentraciones plasmáticas de LH aumentaron (de 0.97 ± 0.41 a 2.80 ± 0.62 ng / mL) en cabras."

"In goats, the permanent presence of bucks rendered sexually active by photoperiodic treatments, prevents the occurrence of seasonal anovulation, and the introduction of these sexually active bucks, induce ovulations during the seasonal anestrus. We used ovariectomized goats bearing subcutaneous implants filled or not with estradiol to determine 1) whether the permanent presence of sexually active bucks prevents the decrease of LH during the seasonal anestrus, and 2) whether the introduction of photostimulated bucks increases the plasma LH concentrations during the seasonal anestrus. In Experiment 1, we used ovariectomized goats bearing 12-mm subcutaneous implants containing estradiol (OVX+E2). One group of goats (n=13) remained in permanent contact with naturally (November-January) or photostimulated, sexually active bucks (February-May); the other group (n=13) remained in permanent contact with control bucks which displayed intense (November January) or weak sexual behavior (February-May). Plasma LH concentrations were high and did not differ between groups from November to January (P>0.05), when control bucks displayed intense sexual behavior. Afterwards, LH concentrations decreased from March (P < 0.05), and remained low until May, when control males displayed weak sexual behavior. On the contrary, LH concentrations did not decrease and remained high from March to May in goats in contact with the photostimulated bucks (P > 0.05). In Experiment 2, two groups of females (n=6 each) bearing 12-mm empty subcutaneous implants were exposed, during the seasonal anestrus, to control or photostimulated bucks; two other groups (n=6 each) bearing 12-mm subcutaneous implants filled with estradiol, were also exposed to control or photostimulated bucks. Plasma LH concentrations did not increase in goats bearing empty implants, when exposed to control (from 2.01 ± 0.26 to 1.98 ± 0.31 ng/mL) or photostimulated bucks (from 2.45 ± 0.29 to 2.42 ± 0.21 ng/mL; P > 0.05). In contrast, plasma LH concentrations increased (from 0.97 ± 0.41 to 2.80 ± 0.62 ng/mL) in goats exposed to the photostimulated bucks and bearing estradiol implants (P < 0.05). We conclude that the permanent presence of sexually active bucks prevented the decrease of plasma LH concentration in OVX+E2 goats during the seasonal anestrus, and that the introduction of the photostimulated bucks increases the plasma LH concentrations in OVX+E2 goats during the seasonal anestrus".

Doctoral thesis

Caprine Reproductive seasonality Estradiol feedback Sexual behavior Photoperiod CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Producción y cambios morfológicos de Pennisetum ciliare cv. H-17 en función de la edad de rebrote y altura de pradera

JONATHAN RAUL GARAY MARTINEZ SANTIAGO JOAQUIN CANCINO BENIGNO ESTRADA DROUAILLET JUAN CARLOS MARTINEZ GONZALEZ ANDRES GILBERTO LIMAS MARTINEZ JAVIER HERNANDEZ MELENDEZ ADELAIDO RAFAEL ROJAS GARCIA (2019)

Dry matter production (DM) and morphological composition were evaluated according to regrowth age (RA; four, six,

and eight weeks) and prairie height (PH) in Pennisetum ciliare cv. H-17, during rainy season (RS) and drought (DS). The variables were total MS (TDM), leaf (LDM), stem (SDM), dead material (DMDM) and PH. A completely randomized design with four repetitions and linear regression analysis was used. During RS, the TDM was similar (p > 0.05) between RA (8342 kg ha-1) and decreased 90% in DS.

Article

Growth rate rainy season dry season leaf area index specific leaf area CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA CIENCIAS AGRARIAS OTRAS ESPECIALIDADES AGRARIAS

Seasonal and successional dynamics of size-dependent plant demographic rates in a tropical dry forest

Irving Saenz Pedroza Richard Feldman Casandra Reyes García Jorge Arturo Meave del Castillo Luz María del Carmen Calvo Irabien FILOGONIO MAY PAT JUAN MANUEL DUPUY RADA (2020)

Tropical forests are globally important for biodiversity conservation and climate change mitigation but are being converted to other land uses. Conversion of seasonally dry tropical forests (SDTF) is particularly high while their protection is low. Secondary succession allows forests to recover their structure, diversity and composition after conversion and subsequent abandonment and is influenced by demographic rates of the constituent species. However, how these rates vary between seasons for different plant sizes at different successional stages in SDTF is not known. The effect of seasonal drought may be more severe early in succession, when temperature and radiation are high, while competition and density-dependent processes may be more important at later stages, when vegetation is tall and dense. Besides, the effects of seasonality and successional stage may vary with plant size. Large plants can better compete with small plants for limiting resources and may also have a greater capacity to withstand stress. Weasked how size-dependent density, species density, recruitment andmortality varied between seasons and successional stages in a SDTF. We monitored a chronosequence in Yucatan, Mexico, over six years in three 0.1 ha plots in each of three successional stages: early (3 5 years-old), intermediate (18 20 years-old) and advanced (>50 years-old). Recruitment, mortality and species gain and loss rates were calculated from wet and dry season censuses separately for large (diameter > 5 cm) and small (1 5 cm in diameter) plants. We used linear mixed-effects models to assess the effects of successional stage, seasonality and their changes through time on demographic rates and on plant and species density. Seasonality affected demographic rates and density of large plants, which exhibited high wet-season recruitment and species gain rates at the early stage and high wet-season mortality at the intermediate stage, resulting in an increase in plant and species density early in succession followed by a subsequent stabilization. Small plant density decreased steadily after only 5 years of land abandonment, whereas species density increased with successional stage. A decline in species dominance may be responsible for these contrasting patterns. Seasonality, successional stage and their changes through time had a stronger influence on large plants, likely because of large among-plot variation of small plants. Notwithstanding the short duration of our study.

Article

CHRONOSEQUENCE RESAMPLING PLANT AND SPECIES DENSITY RECRUITMENT MORTALITY DRY SEASON RAINY SEASON SECONDARY FOREST SUCCESSION COMPETITION ENVIRONMENTAL FILTERING BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA BIOLOGÍA VEGETAL (BOTÁNICA) DESARROLLO VEGETAL DESARROLLO VEGETAL