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In the European rabbit (Oryctolagus cuniculus), a polytocous livestock species, the number of teats indirectly impacts the doe reproduction efficiency and, in turn, the sustainable production of rabbit meat. In this study, we carried out a genome-wide association study (GWAS) for the total number of teats in 247 Italian White does included in the Italian White rabbit breed selection program, by applying a selective genotyping approach. Does had either 8 (n=121) or 10 teats (n=126). All rabbits were genotyped with the Affymetrix Axiom OrcunSNP Array. Genomic data from the two extreme groups of rabbits were also analysed with the single-marker fixation index statistic and combined with the GWAS results. The GWAS identified 50 significant SNPs and the fixation index analysis identified a total of 20 SNPs that trespassed the 99.98th percentile threshold, 19 of which confirmed the GWAS results. The most significant SNP (P=4.31×10−11) was located on OCU1, close to the NUDT2 gene, a breast carcinoma cells proliferation promoter. Another significant SNP identified as candidate gene NR6A1, which is well known to play an important role in affecting the correlated number of vertebrae in pigs. Other significant markers were close to candidate genes involved in determining body length in mice. Markers associated with increased number of teats could be included in selection programmes to speed up the improvement for this trait in rabbit lines that need to increase maternal performances.

RABBIT haemorrhagic disease (RHD) is an acute and lethal form of viral hepatitis in rabbits ( Oryctolagus cuniculus ) with a mortality rate in adults ranging from 70 per cent to 100 per cent. RHD was first reported in China in 1984, in Europe in 1986, where it caused severe losses to rabbit, and in Australia in 1996 (Abrantes and others 2012). RHD is caused by the lagovirus RHD virus (RHDV) in the family Caliciviridae. In the course of its evolution, RHDV split into six genotypes (Kerr and others 2009), all highly pathogenic and virulent. Genotype 6 is the antigenic subtype (RHDVa) that became prevalent in certain countries, including the USA (McIntosh and others 2007). In addition, other enteric non-pathogenic rabbit caliciviruses (RCVs) related to RHDV have been identified in Europe and Australia (Capucci and others 1996, Strive and others 2009, Le Gall-Recule and others 2011a). In 2010, a new lagovirus was identified in France. This virus showed a capsid protein sequence identity of about 80 per cent with RHDV and was able to cause RHD in vaccinated and young rabbits (15–25 days old) (Le Gall-Recule and others 2011a, b). In addition, it showed a distinct antigenic profile and induced an average mortality rate of 20–30 per cent in both experimental infections and natural cases; such a low mortality rate was never observed in the many experimental rabbit infections carried out with other strains of RHDV. The remaining 70–80 per cent of the rabbits survived the infection without showing typical signs of RHD (Le Gall-Recule and others 2011b). Unexpectedly, in autumn 2011, this new virus also caused fatal cases in cape hares ( Lepus capensis var meditteraneus) (Puggioni and others 2013). All these features strongly suggested that the virus was not derived from RHDV but …