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Mesquite (Prosopis sp) and Leucaena leucocephala are widespread legumes, widely used to feed several livestock species and as food source for human populations in several countries. Both mesquite and Leucaena contain several phytoestrogens which might have potential estrogenic effects. Thus, the aim of this study was to evaluate the effects of mesquite pod and Leucaena extracts on several aspects of behavior and reproductive physiology of the male rat. The effects of the extracts were compared with those of estradiol (E2) and of two isoflavones: daidzein (DAI) and genistein (GEN). The following treatments were given to groups of intact male rats: vehicle; mesquite pod extract; Leucaena extract; E2; DAI; GEN. The results indicate that mesquite pod and Leucaena extracts disrupt male sexual behavior in a similar way to DAI and GEN, but less than E2. The main disruptor of sexual behavior was E2, however after 40 and 50 days of administration, both extracts and phytoestrogens disrupted sexual behavior in a similar way to E2. The extracts also increased testicular germ cell apoptosis, decreased sperm quality, testicular weight, and testosterone levels, as phytoestrogens did, although these effects were less than those caused by estradiol. The number of seminiferous tubules with TUNEL-positive germ cells increased in extracts treated groups in a similar way to phytoestrogens groups, and E2 caused the greatest effect. The number of TUNEL-positive cells per tubule increased only in leucaena extract and E2 groups, but not in mesquite- and phytoestrogens- treated groups. Spermatocytes and round spermatids were the TUNEL-positive cells observed in all experimental groups. This effect was associated with smaller testicular weights without atrophy in experimental groups compared with control. Testicular atrophy was only observed in estradiol-treated males. Testosterone decreased in males of all experimental groups, compared with control, this androgen was undetectable in E2 treated males. These results suggest that mesquite pod and Leucaena extracts cause effects similar to those of phytoestrogens in male rat reproduction, these effects were lower than those caused by E2.

Global consumption of phytoestrogens and their effects have increased both in animals and humans due to the augmented use of legumes in animal diets as well as the increase in vegetarian diets in some human populations. Even though the general opinion and that of clinicians toward phytoestrogens is generally positive, many phytoestrogens are now recognized as endocrine disruptor compounds, capable of interfering with the synthesis, secretion, transport, binding, action or elimination of natural hormones in the body that are responsible for reproduction. The effects of phytoestrogens mainly depend on the type, amount and plant species ingested. These compounds are found widely in a variety of plants and fodder, and can have adverse effects mainly on the reproductive tract in most animal species. Many phytoestrogens can act as estrogenic agonists or antagonists, and their effects can vary from infertility to an estrogenic over-response, thus increasing secretions in the reproductive tract and disrupting animal behavior. Presently, there is still a lack of knowledge on this subject, and the effects on reproductive parameters of estrogenic forage in animal production systems are unknown. Therefore, it is necessary to continue research in order to elucidate the effects of phytoestrogens, the doses at which effects are seen, the species, the disruptive or beneficial effects, as well as the mechanisms of action involved. This review focuses on the effects of phytoestrogens in the reproductive physiology of livestock and human, as well as the knowledge obtained from research in animal models., El consumo de dietas a base de leguminosas en los animales de granja, así como así como las dietas vegetarianas y el consumo de suplementos alimenticios con alto contenido de fitoestrógenos en los humanos se han incrementado en los últimos años. Los fitoestrógenos están ampliamente contenidos en gran variedad de leguminosas, pastos, ensilajes y hierbas, y pueden causar efectos adversos principalmente en el tracto reproductivo de la mayoría de las especies animales. Muchos fitoestrógenos pueden actuar como agonistas o antagonistas estrogénicos, por lo que sus efectos varían desde la sobre-respuesta estrogénica, aumentando las secreciones del tracto reproductivo, hasta la infertilidad, alterando además el comportamiento animal. Por lo tanto, se ha considerado a los fitoestrógenos como disruptores o desorganizadores endocrinos, capaces de interferir con la síntesis, la secreción, el transporte, la unión, la acción y eliminación de las hormonas que produce el organismo de forma natural y que son responsables de la reproducción. El efecto de los fitoestrógenos en la reproducción depende básicamente del tipo y la cantidad presente en la especie vegetal que se consuma. A pesar de la abundante literatura que muestra los efectos de los fitoestrógenos en los humanos y en los modelos animales de laboratorio, en la actualidad aún se desconoce el grado en que los parámetros reproductivos en los sistemas de producción animal se han visto afectados por el consumo de forrajes fitoestrogénicos. Por lo tanto, es necesario continuar con investigaciones que permitan dilucidar los efectos de estos compuestos con respecto a las dosis utilizadas, las especies, los efectos nocivos o benéficos, así como los mecanismos de acción involucrados. Esta revisión se centra en los efectos de los fitoestrógenos en diversas especies de ganado y en los humanos, así como en los hallazgos obtenidos de la investigación en modelos animales de laboratorio.