Prevalence of known recessive disease alleles in Italian beef cattle

In the last decade, five different genetic recessive disorders with known molecular causes were reported in Chianina, Marchigiana and Romagnola cattle. Targeted genotyping of the following pathogenic variants affecting five different genes became possible: the two forms of ATP2A1-related pseudomyotonia (PMT) in Chianina and Romagnola, KDM2B-related paunch calf syndrome (PCS) in Marchigiana and Romagnola, NID1-related congenital bilateral cataract (CC) in Romagnola, ABCA12-related ichthyosis fetalis (IF) and FA2H-related ichthyosis congenita (IC) in Chianina. This study aimed to characterize the frequency of the recessive alleles associated with PMT, PCS, CC, IF and IC and to investigate whether the causal variants are breed specific. Top sires used for artificial insemination and young bulls short-listed for the performance test, for a total of 7283 Chianina, 2696 Marchigiana and 1574 Romagnola animals were considered. Carriers rates (CR) considered on the base of the year of birth of the animals ranged as following: CR of PMT-ATP2A1 exon 6 from 8.1% to 22.3% in Chianina, 7.4% to 14.3% in Marchigiana and 0 to 8.1% in Romagnola; CR of PMT-ATP2A1 exon 8 in Romagnola from 3.9% to 13%; CR of CC-NID1 in Romagnola from 3.5% to 8.1%;CR of PCS-KDM2B from 0 to 14.3% in Marchigiana and from 9 to 55.6% in Romagnola; CR of IF-ABCA12 in Chianina from 1.8% to 6.3%; CR of IC-FA2H in Chianina from 3.8% to 31.8%. Considering only the top sires, the CR resulted as following: CR of PMT-ATP2A1 exon 6 was 3.5% in Chianina, and 9.7% in Marchigiana; CR of PMT-ATP2A1 exon 8 in Romagnola was 4%; CR of CC-NID1 in Romagnola was 6%; CR of PCS-KDM2B was 2.2% in Marchigiana and 27.8% in Romagnola; CR of IF-ABCA12 in Chianina was 1.7%; CR of IC-FA2H in Chianina was 15.2%. This study validates the concern regarding the impact of recessively inherited diseases on breeding programs. It also reports the first evidence of the segregation of PMT-ATP2A1 variant initially found in Chianina also in Marchigiana. Systematic genotyping of sires for these alleles is recommended to prevent risky matting.