Bovine Digital Dermatitis (BDD) has become one of the greatest plagues in cattle herds around the world. While the acute phase of this infectious disease is easily identified as lesions at the coronary band of the bovine hoof with the color and shape of strawberries, other stages of the disease, with the infectious agents encapsulated in the skin, are often neglected. In the present study, a total of 6,230 cows were scored repeatedly for disease status in seven large dairy herds in Eastern Germany, differentiating between healthy animals (M0), acute stages (M2), and encapsulated stages (M4). A randomly chosen subset (data set I) of 2,520 animals were genotyped using either a 50-K bead chip or a 10-K bead chip with SNP genotypes imputed to 50-K. Genotypes and phenotypes defined across all observations for each animal were used for single-step genomic best linear unbiased prediction (ssGBLUP). For sires, correlations with official breeding values from the German national system were favorable and significant for EBV for somatic cell score (0.15), longevity (0.20), and the German total merit index RZG (0.14). Genomic EBV for sires were validated in an independent data set (data set II) of 37,021 first, 27,961 second, and 18,293 third lactation disease status scores. However, this data set originated from scores as done by various hoof trimmers who typically only take M2 stages as ‘diseased’. Sires were grouped from low to high susceptibility in five classes according to their genomic EBV from data set I. Sires were identified in data set II and their EBV class code was used in a statistical model for analysis of data set II. Accounting for herd-visit-date and days in milk, least-square means of BDD incidence for EBV classes of sires in data set II were 0.196, 0.191, 0.172, 0.171, and 0.147 for first lactations. Hence, a substantial decrease in the disease frequency can be found with increasing EBV for resistance. Results for later lactations were similar. The results show that even a relatively small data set may be used for prediction of meaningful genomic EBV under the condition that phenotyping is highly accurate and the genetic architecture of the trait favors genomic predictions. Keywords: digital dermatitis, susceptibility, genomic prediction, ssGBLUP, validation
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Disease Resistance 1, , 187, 2018
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