Avaliação individual e racial da qualidade do sêmen canino in natura e criopreservado com diferentes protocolos

• Ano de defesa: 2008
• Autor(a) principal: Mascarenhas, Rebeca Marques
• Orientador(a): Paula, Tarcízio Antônio Rego de
• Banca de defesa: Costa, Deiler Sampaio , Cunha, Isabel Candia Nunes da , Valle, Guilherme Ribeiro , Guimarães, José Domingos
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Medicina Veterinária
• Departamento: Biotecnologia, diagnóstico e controle de doenças; Epidemiologia e controle de qualidade de prod. de
• País: BR
• Palavras-chave em Português: Sêmen; Criopreservação; Cão
• Palavras-chave em Inglês: Sêmen; Cryopreservation; Dogs
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::REPRODUCAO ANIMAL
• Link de acesso: http://locus.ufv.br/handle/123456789/4975

Although the first birth of pups with use of frozen semen has been reported almost 40 years ago, still today the conception rate with thawed canine semen is generally inferior to the observed in other species. Many factors influencing the semen quality through the cryopreservation process are known, including the centrifugation protocol, the extender composition, the association between the cryoprotectors, the cooling rate, the time of equilibrium and the freezing rate, as well as the association between thawing and freezing rates. Individual variations in the semen freezability are found in many species, including the dog. Some authors attribute these variations to the differences in the spermatic membrane lipid composition and spermatozoon sensitivity of the glycerol toxic effects. In present work 36 semen samples where collected, from 12 dog of the: Beagle, Schnauzer, Doberman and Boxer breeds, by digital manipulation. After the collection the semen was centrifuged, reextended in Tris-Citrato extender added with 1, 2, 4 and 6% of glycerol and packaged in 0,25mL straws. After that the semen were cooled for 1 hour until 4oC, then half of the straws of each treatment was immediately freezed and the remain was kept by more 1 hour in equilibrium at 4oC before the freezing. Two freezing rates had been tested in termical box contend liquid nitrogen through the positioning of the straws 5 and 10 cm above the surface of nitrogen per 10 minutes. The thawing was carried through immersion in water 38oC per 1 minute. The semen was evaluated at the moment of the collection, after the centrifugation and immediately after thawing for spermatozoa movement through motility, progressive status, and sperm index and for plasma membrane integrity and viability through hiposmotic swelling tests and live/dead stain. The sperm longevity was evaluated through the thermorresistece test. In the present work the individual averages of sperm motility and progressive status in the fresh semen had varied from 3.5 to 5.0 and 63 to 90% respectively, while the breed averages had varied of 4.4 the 4.9 and 80 to 90% respectively. The semen centrifugation resulted in significant fall of 13% in progressive status and 14% in the motility and spermatic index. The analysis of the parameters of plasma membrane viability and integrity in the semen after centrifugation shows significant reduction of 38% and 14% in the reactive cells to the hiposmotic swelling test and to the supravital coloration respectively. The results of the hiposmotic swelling test, live/dead stain and thermorresistence in the thawed semen demonstrate better performance when protocols of freezing were used with equilibrium time. Influence of the freezing rate, in isolated form, was not observed on the seminal parameters evaluated and significant variations had been only observed when equilibrium time and glycerol concentration were associated. Isolate the increase in the percentage of glycerol from 1 to 6% in the extender composition, promotes prompt improvement to plasma membrane integrity and to spermatic index in the thawed samples. However, when associates the observed results of biggest levels of glycerol to the presence of equilibrium time and to the slow rate of freezing, significant increases are observed in all the studied parameters. Individual variation was observed in spermatic index of thawed semen, but not in the fresh semen. Already the parameters of plasma membrane integrity and viability had presented individual variation in both. When the parameter breeds is evaluated, any significant alterations were observed on the evaluated parameters in fresh semen, however in the thawed semen, significant variations in the plasma membrane integrity and viability had been observed. The dogs of the Schnauzer breed had presented significantly shorter sperm longevity after the thawing. The Doberman and Boxer breeds had presented the best results of freezability in in vitro evaluation. With the exception of the test of live/dead stain, the studied parameters had presented significant correlations between the data collected in fresh semen with those observed in thawed semen.