Short communication: Lethal mutations in Vorderwald cattle through Montbéliarde incrossings

[Comparison of production data and reasons for culling in Hinterwald, Vorderwald, Fleckvieh and Holstein cows from 1953 to 2021]

OBJECTIVE

The primary aim of this study was to determine the current inventory of Hinterwald cows in Baden Wurttemberg and in Switzerland. A secondary goal was to compare the production data and registered reasons for culling in Hinterwald, Vorderwald, Fleckvieh and Holstein dairy cows in order to determine possible differences between extensive and intensive husbandry practices.

MATERIALS AND METHODS

The relevant breeding organization data from 1953 to 2021 were obtained and analyzed. The data of the Hinterwald Breed Association of Switzerland were also included in this study because a large population has been established in the past 40 years.

RESULTS

The number of Hinterwald cows used in dairy production has markedly declined in their original area of distribution in the highland zone of the Southern Black Forest. There is reason to fear that the use of this breed on dairy farms may eventually cease. In contrast, an increase in the number of Hinterwald cattle in extensive farming for meat production was seen in the Black Forest region and in Switzerland. Compared with Vorderwald, Holstein and Fleckvieh cows, the milk yield of Hinterwald cows has not increased significantly over the last 60 years, whereas other production data including fertility parameters, udder health, feet and leg scores and longevity have been outstanding. The breed comparison also revealed that the enormous increase in milk yield in the most popular dairy breeds has occurred at the expense of an unacceptably high disease prevalence and an associated shortened lifespan, often under suboptimal husbandry conditions.

CONCLUSIONS AND CLINICAL RELEVANCE

The Hinterwald breed has survived as a result of the resilience of many farmers, the financial commitment of private organizations and governmental support. The characteristics of Hinterwald cattle are excellent, making this breed an ideal choice for sustainable farming, which is a necessity in view of climate change. It would appear prudent to preserve and support this breed and others as they represent a valuable gene pool.

Activation of cryptic splicing in bovine WDR19 is associated with reduced semen quality and male fertility

Cattle are ideally suited to investigate the genetics of male reproduction, because semen quality and fertility are recorded for all ejaculates of artificial insemination bulls. We analysed 26,090 ejaculates of 794 Brown Swiss bulls to assess ejaculate volume, sperm concentration, sperm motility, sperm head and tail anomalies and insemination success. The heritability of the six semen traits was between 0 and 0.26. Genome-wide association testing on 607,511 SNPs revealed a QTL on bovine chromosome 6 that was associated with sperm motility (P = 2.5 x 10⁻²⁷), head (P = 2.0 x 10⁻⁴⁴) and tail anomalies (P = 7.2 x 10⁻⁴⁹) and insemination success (P = 9.9 x 10⁻¹³). The QTL harbors a recessive allele that compromises semen quality and male fertility. We replicated the effect of the QTL on fertility (P = 7.1 x 10⁻³²) in an independent cohort of 2481 Brown Swiss bulls. The analysis of whole-genome sequencing data revealed that a synonymous variant (BTA6:58373887C>T, rs474302732) in WDR19 encoding WD repeat-containing protein 19 was in linkage disequilibrium with the fertility-associated haplotype. WD repeat-containing protein 19 is a constituent of the intraflagellar transport complex that is essential for the physiological function of motile cilia and flagella. Bioinformatic and transcription analyses revealed that the BTA6:58373887 T-allele activates a cryptic exonic splice site that eliminates three evolutionarily conserved amino acids from WDR19. Western blot analysis demonstrated that the BTA6:58373887 T-allele decreases protein expression. We make the remarkable observation that, in spite of negative effects on semen quality and bull fertility, the BTA6:58373887 T-allele has a frequency of 24% in the Brown Swiss population. Our findings are the first to uncover a variant that is associated with quantitative variation in semen quality and male fertility in cattle.

In cattle farming, artificial insemination is the most common method of breeding. To ensure high fertilization rates, ejaculate quality and insemination success are closely monitored in artificial insemination bulls. We analyse semen quality, insemination success and microarray-called genotypes at more than 600,000 genome-wide SNP markers of 794 bulls to identify a recessive allele that compromises semen quality. We take advantage of whole-genome sequencing to pinpoint a variant in the coding sequence of WDR19 encoding WD repeat-containing protein 19 that activates a novel exonic splice site. Our results indicate that cryptic splicing in WDR19 is associated with reduced male reproductive performance. This is the first report of a variant that contributes to quantitative variation in bovine semen quality.