Brown Swiss fertility haplotype BH14
By Paul VanRaden, Dan Null, and Norm Magnussen
Switzerland last year began reporting a new lethal haplotype in Brown Swiss (BH14) causing early pregnancy loss. Brown Swiss USA received a list of 1,254 carrier bulls from Switzerland and the Animal Genomics and Improvement Lab (AGIL) compared those to haplotype calls for BH14 from CDCB data for the same bulls. In both analyses the haplotype traced primarily to BSUSA175545 VENTURES ESP BABARAY (W) born in 1978, and no homozygotes were detected in CHE or USA analyses. Of the carrier bulls from the CHE file, 94% were also carriers from CDCB data, and 6% of the carriers from CHE data were non-carriers here. Of those 73 non-matching bulls, only 5 were USA bulls and those had no daughters. Likely almost all 43,000 non-carrier bulls matched, and if so, the concordance is very high for BH14. For some bulls, the CHE analysis may have included a gene test for the MRPL55 mutation on chromosome 7 at ARS-UCD1 location 2,996,436. Carrier frequency was 6.1% reported by Häfliger et al. (2021). In CDCB data, the number of genotyped carriers was 1,113 of 16,207 USA animals (6.9%) and across all countries was 2,960 animals of 59,127 genotyped (5.0%) as of April 2022. CDCB conception rate data included less than 100 matings of carrier sires to carrier maternal grandsires (the dam’s sire for the potential embryo being created). A conception loss of about 0.04 or 4% is expected if an extra 1 / 8 of embryos do not survive. The significant effect on fertility reported in CHE was not significant in USA because so few observed matings gave a standard error > 5%. Haplotype or gene tests from CHE may be reported initially, but routine publication of BH14 status in USA will allow selection and mating of males and females to further improve BS fertility.
CDCB should begin reporting haplotype BH14 in the April Genetic Evaluations. The Board has directed that we will go forward with labeling of BH14 carriers.