Resumen En semen de mamíferos, se ha demostrado que la viscosidad influye de manera negativa para su conservación. En semen de aves los estudios sobre las características físicas de los eyaculados son limitados, particularmente la viscosidad no ha sido estudiada. Los medios para la criopreservación, no consideran la viscosidad para mantener la viabilidad espermática. Por lo cual, el objetivo de este estudio fue evaluar el efecto de la viscosidad en el medio para mantener su viabilidad post descongelación. Se determinó los parámetros de evaluación básica, de maduración y reacción acrosomal evaluando la presencia y distribución de Ca2+ mediante la co-incubación con clortetraciclina. Se realizaron 25 evaluaciones de pool seminal, criopreservados en medio Lake suplementado con 6 % de dimetilacetamida y con 0 % (Testigo), 10 %, 30 % y 45 % de ficoll, para ajustar la viscosidad del medio a condiciones similares a las del semen y del líquido oviductal y a un grado mayor de viscosidad. La movilidad espermática fue menor (P(0.05) en alícuotas con mayor porcentaje de ficoll. El porcentaje de espermatozoides vivos fue similar (P>0.05) en el testigo y todas las alícuotas con diferente porcentaje de ficoll. La maduración espermática presentó un mayor (P(0,05) porcentaje de espermatozoides no capacitados cuando se utilizó 10% de ficoll. De manera inversa el porcentaje de espermatozoides con reacción acrosomal fue menor (P(0,05) también cuando se utilizó 10 % de ficoll. Los resultados de este estudio demuestran que variaciones en el grado de viscosidad del medio, pueden mantener o incrementar la viabilidad espermática post descongelación.

Abstract In mammalian semen, viscosity has been shown to have a negative influence on its conservation. In bird semen, studies on the physical characteristics of ejaculates are limited, particularly viscosity has not been studied. The media for cryopreservation do not consider viscosity to maintain sperm viability. Therefore, the objective of this study was to evaluate the effect of viscosity on the medium to maintain its viability after thawing. The parameters of basic evaluation, maturation and acrosome reaction were determined, evaluating the presence and distribution of Ca2+ through co-incubation with chlortetracycline. Twenty-five (25) evaluations of seminal pool were performed, cryopreserved in Lake medium supplemented with 6 % dimethylacetamide and with 0 % (Control), 10 %, 30 % and 45 % ficoll, to adjust the viscosity of the medium to conditions similar to those of semen and oviductal fluid and to a higher degree of viscosity. Sperm motility was lower (P(0.05) in aliquots with a higher percentage of ficoll. The percentage of live spermatozoa was similar (P>0.05) in the control and all aliquots with different percentage of ficoll. Sperm maturation presented a higher (P(0.05) percentage of non-capacitated spermatozoa when 10 % ficoll was used. Conversely the percentage of spermatozoa with acrosome reaction was also lower (P(0.05) when 10 % ficoll was used. The results of this study show that variations in the degree of viscosity of the medium can maintain or increase sperm viability after thawing.

Abstract Nowadays, the third part of parrots in the world is endangered or vulnerable; an alternative for their preservation is assisted reproduction in captivity through hormonal manipulation. In birds, GnRH is the main hormone which controls reproductive physiology, it is known there are three types: GnRH-I, GnRH-II and GnRH-III, involved in the release or inhibition of luteinizing hormone and follicle stimulant hormone to control gonadal and gametic development. The objective of this study was, to evaluate the effect of administrating synthetic GnRH-I in the testicular development of Melopsittacus undulatus. Twenty-eight adult budgerigars were randomly divided in two groups: control (n=14) and treated (n=14) with a unique dose of synthetic GnRH-I. Testicular development was assessed through ultrasonography and density was evaluated with pixels. Germinal diameter and thickness of germinal epithelium were determined with histology; there were identified and countified different cellular strains in seminiferous tubules therefore spermatobioscopy. Results. Ecographic density was: control group: 76 ± 7 pixels, treated group 41 ± 3 pixels. Thickness of germinal epitellium, 51.5 ± 2.9µm and 73.1 ± 3.1µm, for control group and treated group respectively. Sperm concentration in the treated group was 300% superior than in control group. It is concluded that the administration of synthetic GnRH-I, is a viable alternative to be used as part of the assisted reproductive techniques to induce reproduction.