Accuracy of genomic predictions in Gyr (Bos indicus) dairy cattle.

Genomic selection may accelerate genetic progress in breeding programs of indicine breeds when compared with traditional selection methods. We present results of genomic predictions in Gyr (Bos indicus) dairy cattle of Brazil for milk yield (MY), fat yield (FY), protein yield (PY), and age at first calving using information from bulls and cows. Four different single nucleotide polymorphism (SNP) chips were studied. Additionally, the effect of the use of imputed data on genomic prediction accuracy was studied. A total of 474 bulls and 1,688 cows were genotyped with the Illumina BovineHD (HD; San Diego, CA) and BovineSNP50 (50K) chip, respectively. Genotypes of cows were imputed to HD using FImpute v2.2. After quality check of data, 496,606 markers remained. The HD markers present on the GeneSeek SGGP-20Ki (15,727; Lincoln, NE), 50K (22,152), and GeneSeek GGP-75Ki (65,018) were subset and used to assess the effect of lower SNP density on accuracy of prediction. Deregressed breeding values were used as pseudophenotypes for model training. Data were split into reference and validation to mimic a forward prediction scheme. The reference population consisted of animals whose birth year was ≤2004 and consisted of either only bulls (TR1) or a combination of bulls and dams (TR2), whereas the validation set consisted of younger bulls (born after 2004). Genomic BLUP was used to estimate genomic breeding values (GEBV) and reliability of GEBV (R2PEV) was based on the prediction error variance approach. Reliability of GEBV ranged from ∼0.46 (FY and PY) to 0.56 (MY) with TR1 and from 0.51 (PY) to 0.65 (MY) with TR2. When averaged across all traits, R2PEV were substantially higher (R2PEV of TR1 = 0.50 and TR2 = 0.57) compared with reliabilities of parent averages (0.35) computed from pedigree data and based on diagonals of the coefficient matrix (prediction error variance approach). Reliability was similar for all the 4 marker panels using either TR1 or TR2, except that imputed HD cow data set led to an inflation of reliability. Reliability of GEBV could be increased by enlarging the limited bull reference population with cow information. A reduced panel of ∼15K markers resulted in reliabilities similar to using HD markers. Reliability of GEBV could be increased by enlarging the limited bull reference population with cow information.

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.