A validation study of loci associated with mastitis resistance in two French dairy sheep breeds

Abstract

Background The identification of loci associated with resistance to mastitis or of the causative mutations may be helpful in breeding programs for dairy sheep as it is for cattle worldwide. Seven genomic regions that control milk somatic cell counts, an indirect indicator of udder infection, have already been identified in sheep (Spanish Churra, French Lacaune and Italian Sardinian–Lacaune backcross populations). In this study, we used a 960 custom-designed ovine single nucleotide polymorphism (SNP) chip in Lacaune and Manech Tête Rousse dairy sheep to validate these seven genomic regions associated with mastitis. Results The most significant SNP ( rs868996547) on Ovis aries chromosome (OAR) 3 was a previously described mutation in the suppressor of cytokine signalling 2 ( SOCS2 ) gene. An antagonist effect of this causal candidate between health and growth in Lacaune sheep was confirmed. Effects of the mutation on the infectious status of the udder, i.e. increases in milk somatic cell counts and bacteria shedding, were also identified. This SNP was not present in the data available on Manech Tête Rousse. Three other regions associated with mastitis were also confirmed on OAR16 (Manech Tête Rousse), 19 (Lacaune) and 2 (both breeds). For the OAR2 region, we validated previously detected SNPs in several other breeds (Sarda, Churra, and Chios). For significant SNPs in the four mastitis regions, the effect varied from 0.24 to 0.67 phenotypic standard deviation of the traits. Two of the mastitis quantitative trait loci (QTL) regions (OAR2 and 16) that we validated here were also associated in opposite ways with milk production traits in both populations. Conclusions These results indicate, at least in part, a genomic basis for the trade-off between milk production and mastitis resistance. Four of the seven mastitis QTL regions that were previously identified in independent populations, were confirmed in this study, which demonstrates partial sharing of mastitis-related genetic mechanisms between different distant dairy sheep populations.

Association of Breed of Sheep or Goats with Somatic Cell Counts and Total Bacterial Counts of Bulk-Tank Milk

“…The development of genomic methods and tools for applications to sheep and the sequencing of the sheep genome [29] have greatly contributed in those efforts [13,30]. In a recent study, Oget et al [31] have confirmed the QTL regions associated with mastitis resistance in sheep of that breed.…”

Genetic polymorphism in European and African sheep breeds reared in Hungary based on 48 SNPs associated with resistance to gastrointestinal parasite infection using KASP-PCR technique

“…A panel of 48 SNPs from 11 parasite-resistance genes located on 8 chromosome was chosen based on previous genome-wide association studies (GWAS) and marker-assisted selection studies (Carracelas et al 2022 ; Oget et al 2019 ; Archibald et al 2010 ) across the sheep genome (Table 1 ). The SNP data for Ovis were obtained from the NCBI’s Single Nucleotide Polymorphism Database (dbSNP http://www.ncbi.nlm.nih.gov ) or Ensembl ( http://www.ensembl.org ).…”

Genome-Wide Association Studies of Somatic Cell Count in the Assaf Breed

“…Since 2007, when the sheep genome was first sequenced, the development of low- and high-density ovine single nucleotide polymorphisms (SNP) chips [ 13 ] has allowed genome-wide association studies to reveal the genetic background of several diseases, including mastitis susceptibility in sheep [ 14 , 15 , 16 , 17 ]. These studies have highlighted several genome regions and some candidate genes, some of which are immune- and body growth-related, distributed on different chromosomes [ 16 , 17 , 18 , 19 ]. Despite this challenge in sheep, genome-wide association studies for mastitis have remained limited [ 3 ].…”