Effect of viscosity on the medium for rooster (Gallus gallus) sperm cryopreservation

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.