Montserrat Torremorell

Genetic parameters for performance traits in commercial sows estimated before and after an outbreak of porcine reproductive and respiratory syndrome.

Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), is globally the most economically important disease in commercial pigs, and novel control strategies are sought. This paper explores the potential to use host genetics to decrease the impact of PRRS on reproductive sows. Commercial pig data (7,542 phenotypic records) from a farm undergoing an outbreak of PRRSV were analyzed to assess the impact of PRRS on reproductive traits and the inheritance of such traits. First, differing methodologies were used to partition the data into time periods when the farm was disease free and when the farm was experiencing PRRSV outbreaks. The methods were a date/threshold method based on veterinary diagnosis and a threshold/threshold method based on trends in underlying performance data, creating the DTD and TTD data sets, respectively. The threshold/threshold method was more stringent in defining periods when PRRS was likely to be having an impact on reproductive performance, resulting in a data set (TTD) that was slightly smaller (1,977 litters from 1,526 sows) than that from the date/threshold method (3,164 litters and 1,662 sows), and it showed more pronounced impacts of PRRS on performance. Impacts on performance included significant increases in mean values of mummified and stillborn piglets (0.04 to 1.13 and 0.63 to 1.02, respectively) with a significant decrease in total born alive (10.3 to 9.08). Estimated heritabilities during the healthy phase were generally less (mummified piglets = 0.03 +/- 0.01, matings per conception = 0.04 +/- 0.01) than during the PRRSV outbreak (TTD data set; mummified piglets = 0.10 +/- 0.03, matings per conception = 0.46 +/- 0.04). These results imply genetic variation for host resistance to, or tolerance of, PRRSV, particularly with the TTD data set. Genetic correlations between reproductive traits measured in the healthy phase and TTD data set varied from effectively zero for traits describing numbers of mummified or dead piglets to strongly positive for litter size traits. This indicates genetic variation in piglet losses during PRRSV outbreaks is independent of genetic variation in the same traits in healthy herds. In summary, our findings show that there is within-breed genetic variation for commercially relevant traits that could be exploited in future breeding programs against PRRSV infection. Selection for increased PRRS resistance would be desirable to the industry because effective control measures remain elusive.

Toll-like receptor 4 genetic diversity among pig populations.

The transmembrane glycoprotein encoded by the Toll-like receptor 4 gene (TLR4) acts as the transducing subunit of the lipopolysaccharide receptor complex of mammals, which is a major sensor of infections by Gram-negative bacteria. As variation in TLR4 may alter host immune response to lipopolysaccharide, the association between TLR4 polymorphisms and immune traits of the respiratory and gut systems has important implications for livestock. Here, a sequence dataset from 259 animals belonging to commercial and traditional European pig populations, consisting of 4305 bp of TLR4, including the full transcribed region, a portion of intron 2 and the putative promoter region, was used to explore genetic variation segregating at the TLR4 locus. We identified 34 single nucleotide polymorphisms, 17 in the coding sequence and 17 in the non-coding region. Five non-synonymous mutations clustered within, or in close proximity to, the hypervariable domain of exon 3. In agreement with studies in other mammals, a major exon 3 haplotype segregated at high frequency in the whole sample of 259 pigs, while variants carrying non-synonymous substitutions showed frequencies ranging between 0.6% and 8.7%. Although results on exon 3 provided suggestive evidence for purifying selection occurring at the porcine TLR4 gene, the analysis of both coding and non-coding regions highlighted the fact that demographic factors strongly influence the tests of departure from neutrality. The phylogenetic analysis of TLR4 identified three clusters of variation (ancestral, Asian, European), supporting the evidence of Asian introgression in European main breeds and the well documented history of pig breed domestication previously identified by mtDNA analysis.

Improving pig health through genomics: a view from the industry.

Health is one of the most important contributors to animal welfare, productivity and profitability in pig production today. For the past 30 years, pig breeders have focused on genetic improvement of lean growth, feed efficiency, meat quality and reproduction. However, in recent years, selection objectives have been broadened to include livability, robustness and disease resistance. A DNA marker for selection of resistance to F18+ E. coli has been available for several years. This marker decreases mortality and improves growth on farms experiencing post-weaning scours and/or oedema disease. However, for most diseases affecting intensive production systems such as porcine reproductive and respiratory syndrome (PRRS), porcine circovirus type 2-associated diseases (PCVAD), Haemophilus parasuis, and swine influenza virus, resistance is a complex and polygenic trait. Selection for improved resistance to these diseases will be incremental and require use of multiple markers in complex breeding schemes. Novel technologies such as pig gene microarrays, single nucleotide polymorphism (SNP) panels and advanced bioinformatics are being used to identify new health candidate genes for these economically important diseases. Lagging behind, however, is availability of large DNAdatasets from pedigreed populations with accurately measured health phenotypes that are needed to identify associations between SNPs and health traits. Increased focus on datasets with health traits will be the key to finding useable discoveries with new genomics technologies. Currently, the industry uses dozens of SNP markers to increase the accuracy of selection for complex breeding objectives, including disease resistance. As the pig genome is sequenced and barriers to genotyping thousand of markers are eliminated, genomic selection for health traits will receive increasing attention from commercial breeders.

Animal genomics for animal health report: Critical needs, problems to be solved, potential solutions, and a roadmap for moving forward

The first International Symposium on Animal Genomics for Animal Health, held at the World Organisation for Animal Health (OIE) Headquarter, 23-25 October, 2007, Paris, France, assembled more than 250 participants representing research organizations from 26 countries. The symposium included a roundtable discussion on critical needs, challenges and opportunities, and a forward look at the potential applications of animal genomics in animal health research. The aim of the roundtable discussion was to foster a dialogue between scientists working at the cutting edge of animal genomics research and animal health scientists. In an effort to broaden the perspective of the roundtable discussion, the organizers set out four priority areas to advance the use of genome-enabled technologies in animal health research. Contributions were obtained through open discussions and a questionnaire distributed at the start of the symposium. This symposium report provides detailed summaries ofthe outcome ofthe roundtable discussion for each of the four priority areas. For each priority, the problems needing to be solved, according to the views of the participants, are identified, including potential solutions, recommendations, and lastly, concrete steps that could be taken to address these problems. This report serves as a roadmap to steer research priorities in animal genomics research.