Eficiência da congelação automatizada na viabilidade de sêmen bovino.

Abstract

Even with technological advances in the field of artificial insemination, there is a huge number of people freezing semen in a manual way. This technique has proven to be viable, however, it is difficult to standardize the cooling and freezing curves, since they depend on the quality of the material used (refrigerator sealing, type of cooler, liquid nitrogen level and other). Therefore, the objective of this study was to evaluate the effect of the cryopreservation of bovine semen using two freezing techniques (conventional and automated) on motility, vigor and heat resistance of the sperm after thawing. The experiment was developed over a period of 12 weeks, divided into two parts, an initial six weeks part where Tris-yolk extender was used and a second part in which the extender used was Citrate-yolk. Three Holstein bulls were used for weekly semen collection by artificial vagina method. After collection, were evaluated: volume, motility, mass motility and sperm concentration to find out the number of doses. After dilution, the semen was stored in straws of 0.5 ml. Then the straws were subjected to conventional freezing technique (use of refrigerator, nitrogen vapor and immersion in liquid nitrogen) and automated technique (machine from Cryogen ®). After 24 hours the samples were thawed, re-tested and underwent the quick thermoresistance test. The results were analyzed by Kruskal-Wallis analysis of variance (nonparametric) with a significance level of 5% with the aid of BioEstat 4 and Systat 11 PC-programs. There was significant difference (p <0.05) between automated and manual techniques for both extenders used, and the automated technique has presented the best results for motility and vigor after cryopreservation and thermoresistance test. Thus, we can conclude that the automated technique to freezing bovine semen has shown to be advantageous and practical because as well as providing better results, it standardizes cooling and freezing curves.