Genomic selection and assisted reproduction technologies to foster cattle breeding

Genomics has been propagated as a “paradigm shifting” innovation in livestock during the last decade. The possibility of predicting breeding values using genomic information has revolutionized the dairy cattle industry and is now being implemented in beef cattle. In this paper we discuss how genomics is changing cattle breeding through genomic selection, and how this change is creating new ways to articulate assisted reproduction technologies with animal breeding. We also debate that the scientific community is still starting the long journey to reveal the functional aspects of the cattle genome, and that knowledge in this field is the frontier to a whole new venue for the development of novel applications in the livestock sector.

Genomic selection and assisted reproduction technologies to foster cattle breeding

Genomics has been propagated as a “paradigm shifting” innovation in livestock during the last decade. The possibility of predicting breeding values using genomic information has revolutionized the dairy cattle industry and is now being implemented in beef cattle. In this paper we discuss how genomics is changing cattle breeding through genomic selection, and how this change is creating new ways to articulate assisted reproduction technologies with animal breeding. We also debate that the scientific community is still starting the long journey to reveal the functional aspects of the cattle genome, and that knowledge in this field is the frontier to a whole new venue for the development of novel applications in the livestock sector.(AU)

Assessment of swim-up and discontinuous density gradient in sperm sex preselection for bovine embryo production / Avaliação do swim-up e do gradiente descontinuo de densidade na pré-seleção do sexo de espermatozoides na produção de embriões bovinos

The purpose of this work was to associate the modified swim-up method with centrifugation in density gradient for the separation of X-bearing spermatozoa. Sperm viability and integrity were evaluated through the Trypan Blue/Giemsa staining method. Quality control of centrifuged spermatozoa was performed in in vitro produced embryos. The results were validated by the sex ratio of in vitro produced embryos using PCR by Y- specific sequences present in bovine male genomic DNA. After determining genetic sex of in vitro produced embryos, the results showed difference (P<0.05) in deviation of sex ratio when comparing the control group (45.2% females) with the other spermatozoa selection procedures (60.6% females) (P<0.05). The sperm selection methods are capable of selecting X-bearing spermatozoa without compromising the spermatozoa fertility (cleavage and blastocyst rates, 70% and 26%, respectively) and were considered relevant methods to be introduced in bovine in vitro produced embryo programs.(AU)

O objetivo do presente trabalho foi associar o método de swim-up modificado à centrifugação em gradiente de densidade para a separação de espermatozoides portadores do cromossomo X. A viabilidade e a integridade espermática foram avaliadas pelo método de coloração Azul de Tripan e Giemsa. O controle de qualidade dos espermatozoides centrifugados foi realizado por meio da produção in vitro de embriões bovinos. Os resultados foram validados pela técnica de PCR para verificar a proporção sexual dos embriões produzidos in vitro, com o uso de sequências Y especificas presente no DNA genômico de machos bovinos. Após determinar o sexo genético dos embriões produzidos in vitro, os resultados não mostraram diferença (P<0,05) no desvio da proporção do sexo quando comparou o grupo controle (45,2% de fêmeas) com os outros processos de seleção de espermatozoides (60,6% de fêmeas) (P<0,05). Os métodos de seleção de espermatozoides são capazes de selecionar espermatozoides portadores do cromossomo X sem comprometer a fertilidade, medida pelas taxas de clivagem e blastocisto de 70% e 26%, respectivamente, e foram considerados métodos de relevância para serem introduzidos nos programas de produção in vitro de embriões bovinos.(AU)

High incidence of testicular hypoplasia in Brangus-Ibagé bulls in Mato Grosso do Sul state: case report / Alta incidência de hipoplasia testicular em touros Brangus-Ibagé no estado do Mato Grosso do Sul: relato de caso

This study describes a high incidence of testicular hypoplasia observed during breeding soundness examination conducted on a commercial farm in Mato Grosso do Sul state. Sixty-eight Brangus-Ibagé bulls aged between 36 and 48 months were evaluated and eight animals were diagnosed with testicular hypoplasia, which corresponded to an incidence of 11.8%. The hypoplastic animals presented flaccid testicular consistency and small size of scrotal circumference (mean of 28.9 cm) compared with the other animals evaluated, which presented a firm-elastic testicular consistency and mean scrotal circumference of 36.6 cm. In the semen evaluation of hypoplastic animals, low progressive motility (mean of 47%) and high percentage of major and total defects (means of 56% and 62%, respectively) were observed. The animals that were approved in the breeding soundness examination presented mean progressive motility, major defects and total defects of 68%, 17% and 23%, respectively. Given the genetic character of testicular hypoplasia, the immediate removal of hypoplastic animals from breeding was recommended. Finally, it was suggested to investigate the origin of these animals in order to avoid that new animals from this lineage are acquired by the owner.

Neste trabalho, relata-se um caso de alta incidência de hipoplasia testicular observada durante exame andrológico realizado em uma fazenda comercial no estado do Mato Grosso do Sul. Foram avaliados 68 touros Brangus-Ibagé com idade entre 36 e 48 meses e observou-se oito animais com hipoplasia testicular, o que correspondeu a uma incidência de 11,8% desta patologia. Os animais hipoplásicos apresentaram consistência testicular flácida, bem como tamanho médio do perímetro escrotal bastante reduzido (28,9 cm) em comparação aos demais animais avaliados, que apresentaram média do perímetro escrotal de 36,6 cm e consistência testicular firme-elástica. Na avaliação do sêmen dos animais com hipoplasia testicular, observou-se baixa motilidade progressiva (média de 47%) e alta porcentagem de defeitos maiores e totais (média de 56% e 62%, respectivamente). Nos demais animais aprovados no exame andrológico, a média de motilidade progressiva, defeitos maiores e defeitos totais foram 68%, 17% e 23%, respectivamente. Dado o caráter genético da hipoplasia testicular, recomendou-se o descarte ou retirada imediata destes animais da reprodução. Por fim, sugeriu-se a investigação da origem destes animais de modo a evitar-se que novos animais oriundos dessa linhagem genética sejam adquiridos pelo proprietário.