Short communication: Prevalence of deleterious variants causing recessive disorders in Italian Chianina, Marchigiana and Romagnola cattle.

In the last two decades, the molecular cause of six monogenic autosomal recessive disorders has been identified in native Italian beef cattle: two different ATP2A1 variants for the pseudomyotonia congenita, the first in Chianina and Romagnola (PMT1) and the second in Romagnola (PMT2); a KDM2B variant for the paunch calf syndrome (PCS) in Marchigiana and Romagnola; a NID1 variant for the congenital cataract (CC) in Romagnola; a LAMB1 variant for the hemifacial microsomia (HFM) in Romagnola; an ABCA12 variant for the ichthyosis fetalis (IF) in Chianina and a FA2H variant for the ichthyosis congenita (IC) in Chianina. The aim of this study was to evaluate the potential impact of these disorders in the affected Italian populations. For this purpose, 3331 Chianina, 2812 Marchigiana and 1680 Romagnola bulls born in the last 40 years were considered. The allelic frequency (AF) of the variant for PMT1 was 1.0% in Romagnola, 4.6% in Marchigiana and 5.9% in Chianina. The AF of the variant for PMT2 was 3.3% in Romagnola and 0% in the other two breeds. The AF of the variant for PCS was 11.7% in Romagnola, 2.0% in Marchigiana and 0% in Chianina. The AF of the variants for CC, HFM, IF and IC resulted below 3%, being the variants detected only in the breed populations in which they were previously reported. Considering a selected male population in the single breed, Chianina showed carrier prevalence of 11.9% for PMT1, 7.7% for IC and 6.4% for IF. Romagnola showed carrier prevalence of 23.4% for PCS, 6.7% for PMT2, 4.1% for HFM, 3.2% for CC and 2.0% for PMT1. Marchigiana showed carrier prevalence of 9.1% for PMT1 and 4.0% for PCS. With respect to the Romagnola cattle, the concerning presence of a total of five defect alleles in the population hampers a general approach based on the prevention of carriers from artificial insemination. However, identification of carriers may allow conscious mating to prevent the risk of homozygous descendants as well as the spread of heterozygous offspring. Therefore, systematic genotyping for all seven known harmful alleles is recommended to prevent risk mating between carriers, in particular to avoid the occurrence of affected offspring.

Influence of single nucleotide polymorphisms in the myostatin and myogenic factor 5 muscle growth-related genes on the performance traits of Marchigiana beef cattle.

The Marchigiana is famous for its large body size and favorable dressing percentage. A myostatin (MSTN) gene mutation (a G to T transversion) was identified in the breed. The homozygote "GG" yields a "normal" phenotype, the homozygote "TT" yields a double muscled body shape but sometimes causes survival problems, and the heterozygote genotype produces an extremely muscled body without defects. In practice, Marchigiana "TT" homozygotes are culled from reproduction, but the heterozygotes are chosen as sires. The objective of this study was to assess genes involved in Marchigiana muscle development to improve selection procedures. The effects of the MSTN and myogenic factor 5 (MYF5) genes on the growth and muscle traits in the Marchigiana breed were assessed. The effects of MSTN together with the genotype of the causative mutation (g.874G > T) and the effects of the two SNP in the promoter were studied (g.-371T > A and g.-805G > C). The SNP effects were evaluated in a comparison between the means of the several genotypes or for the average gene substitution and dominance effect. Two hundred forty-nine bullocks were evaluated using a performance test. At the beginning and end of the trial, the animals were weighed and their bodies were measured every 21 d up to 12 mo of age. In addition to these observations, morphological scores and the BLUP indices were estimated at the end of the performance test. The obtained results suggested that the MSTN g.874G > T and MYF5 SNP could be considered in the selection program of the Marchigiana breed. A MSTN g.874G > T genotyping service for the breeders could help to avoid the "TT" genotype and to select for the "GT" genotype. The "AA" MYF5 SNP genotype could also be selected for even if good muscle development yields a certain size reduction.

Prevalence of paunch calf syndrome carriers in Italian Romagnola cattle.

The term 'paunch calf syndrome' encompasses the multi-organic lethal developmental dysplasia reported in the Romagnola breed of cattle and is characterised by facial deformities, an enlarged and floating abdomen containing considerable abdominal effusion, and hepatic fibrosis. Paunch calf syndrome is caused by a missense mutation in the KDM2B gene (c.2503G>A) that is thought to lead to an amino acid exchange (p.D835N). In this study, the prevalence of carriers of the mutant KDM2B allele (and thus the frequency of the allele) was assessed in selected subpopulations of Romagnola cattle. The prevalence of carriers within top-ranked Romagnola sires over the years 2007-2012 was 29.3% (allele frequency 14.6%). In young bull calves, 30.9% were carriers with an allele frequency of 15.4%.

Genetics of slaughter precocity, carcass weight, and carcass weight gain in Chianina, Marchigiana, and Romagnola young bulls under protected geographical indication.

The aim of this study was to estimate the heritability and genetic correlation of age at slaughter (AS), as an indicator of slaughter precocity, carcass weight (CW), and CW gain (CWG = CW × AS(-1)) obtained from young bulls of 3 Italian autochthonous beef cattle breeds [i.e., Chianina (CHI), Marchigiana (MAR), and Romagnola (ROM)]. In addition, the study aimed at evaluating the effect of corrected or uncorrected CW for AS, and analyzing the relationship between adjusted or unadjusted CW with CWG in term of changes in rank correlation in groups of sires with high accuracy. Data were obtained from the Consortium of protected geographical indication (PGI) "Vitellone Bianco dell'Appennino Centrale" (i.e., white young bull of Central Apennines), approved by the European Union. After editing, 20,872 complete records were retained for subsequent Bayesian analysis. Univariate animal model produced h(2) estimates of medium value for AS (i.e., from 0.28 for CHI to 0.39 for the ROM breed). The CW presented h(2) estimates less than AS, ranging from 0.13 for CHI to 0.24 for ROM bulls. The adjustment of CW by AS (CWU-AS) increased the h(2) values for CW in all breeds (i.e., from 0.20 to 0.29). Point estimate of genetic correlations between AS and CW obtained by a bivariate analysis were moderate to low, and negative in all breeds (from -0.08 to -0.29). Rerankings of sire for univariate CW (CWU) analysis and CWU-AS were more noticeable for CHI and ROM (rank correlation of 0.875 and 0.897, respectively) than for the MAR breed (rank correlation of 0.967). Comparing bivariate EBV for CW with EBV for CWU or CWU-AS increased rank correlation to 0.937 for ROM, but for CHI it remained lower (i.e., 0.861), indicating a possible large reranking of sires by correcting CW for AS in this breed. Daily CWG presented h(2) estimates greater than CW and similar or greater than AS. It appears to be a good indicator of instant growth rate capacity of the animal but lacking information on the endpoint of fattening in terms of age and weight. Field slaughter data for the CHI, MAR, and ROM breeds under the PGI labeling indicate that AS is not a mere environmental factor to be corrected for but trait subjected to genetic control. Because of its economic relevance in fattening, age at slaughter, as an indicator of slaughter precocity, could become a trait requiring careful consideration for selection of beef breeds.