Comparison of five extenders for canine semen freezing

Semen was collected from six stud dogs to compare five extenders in the semen freezing process. Each ejaculate was divided in five parts and added to tris-fructose-citric acid, glicine, lactose, skim milk and tris-fructose-citrate extenders. The semen was diluted at 37ºC in extenders without glycerol, in the ratio 1:1 and cooled for 60 minutes to reach a 5ºC temperature. Then, extenders with glycerol in the ratio of 2:1 were added to give the final prefreezing concentration of 4 per cent of glycerol. The diluted semen with the cryoprotectant was maintained for a further 60 minutes in refrigeration to equilibrate the spermatozoa in the glycerol and packaged in 0.5 ml plastic straws. The straws were maintained for 30 minutes in vapor, plunged and stored in liquid nitrogen. Sperm morphology was evaluated before and after freezing, whereas progressive motility (per cent) and velocity of forward progression (0-5) were appraised in different periods of the freezing process. The extender tris-fructose-citric acid showed the best post thaw progressive motility and velocity of forward progression compared to the others extenders. Semen freezing increased major sperm morphological abnormalities, regardless of the extender

Comparison of five extenders for canine semen freezing / Comparação entre cinco diluidores na congelação de sêmen de cães

Semen was collected from six stud dogs to compare five extenders in the semen freezing process. Each ejaculate was divided in five parts and added to tris-fructose-citric acid, glicine, lactose, skim milk and tris-fructose-citrate extenders. The semen was diluted at 37C in extenders without glycerol, in the ratio 1:1 and cooled for 60 minutes to reach a 5C temperature. Then, extenders with glycerol in the ratio of 2:1 were added to give the final prefreezing concentration of 4% of glycerol. The diluted semen with the cryoprotectant was maintained for a further 60 minutes in refrigeration to equilibrate the spermatozoa in the glycerol and packaged in 0.5 ml plastic straws. The straws were maintained for 30 minutes in vapor, plunged and stored in liquid nitrogen. Sperm morphology was evaluated before and after freezing, whereas progressive motility (%) and velocity of forward progression (0-5) were appraised in different periods of the freezing process. The extender tris-fructose-citric acid showed the best post thaw progressive motility and velocity of forward progression compared to the others extenders. Semen freezing increased major sperm morphological abnormalities, regardless of the extender.

Foram utilizados ejaculados de 6 cães para comparar cinco diluidores no processo de congelação de sêmen. Cada ejaculado foi dividido em 5 partes e adicionadas aos diluidores tris-fructose-ácido cítrico, glicina, lactose, leite desnatado e tris-fructose-ácido cítrico. O sêmen foi diluído a 37C sem adição de glicerol na proporção 1:1 (fração A) e refrigerado durante 60 minutos até atingir a temperatura de 5ºC, quando foi adicionada a fração dos diluidores contendo glicerol (fração B) na proporção 2:1, atingindo a concentração final de 4% de glicerol. O sêmen diluído permaneceu por 60 minutos em refrigeração para equilíbrio no glicerol, sendo envasado em palhetas de 0,5 ml, mantido por 30 minutos no vapor de nitrogênio e imerso e armazenado em nitrogênio líquido. Foram avaliados a motilidade progressiva retilínea, o vigor e os defeitos espermáticos antes da congelação e após a descongelação do sêmen em água a 37C. Os resultados mostraram que os diluidores tris-fructose-ácido cítrico e glicina apresentaram as melhores médias de motilidade progressiva retilínea e de vigor espermático após a descongelação. A congelação aumentou a freqüência dos defeitos espermáticos maiores independente do diluidor.