Eli Gjerlaug Enger

The proceedings of the 12th World Congress on Genetics Applied to Livestock Production provide you with 816 papers representing the leading research in livestock genetics around the globe. This boo...

In pigs, crossbreeding aims at exploiting heterosis, but heterosis is difficult to quantify. Heterozygosity at genetic markers is easier to measure and could potentially be used as an indicator of heterosis. The objective of this study was to investigate the effect of heterozygosity on various maternal and production traits in purebred and crossbred pigs. The proportion of heterozygosity at genetic markers across the genome for each individual was included in the prediction model as a fixed regression across or within breeds. Estimates of regression coefficients of heterozygosity showed large effects for some traits. For maternal traits, regression coefficient estimates were always in a favourable direction, while for production, meat and slaughter quality traits, they were both favourable and unfavourable. Traits with the largest estimated effects of heterozygosity were total number born, litter weight at 3 weeks, weight at 150 days, and age at 40 kg. Estimates of regression coefficients on heterozygosity differed between breeds. Traits with the largest effect of heterozygosity also showed a significant (P < 0.05) increase in prediction accuracy when heterozygosity was included in the model compared to the model without heterozygosity. For traits with the largest estimates of regression coefficients on heterozygosity, the inclusion of heterozygosity in the model improved prediction accuracy. Using models that include heterozygosity would result in selecting different animals for breeding, which has the potential to improve genetic gain for these traits. This is most beneficial when crossbreds or several breeds are included in the estimation of breeding values and is relevant to all species, not only pigs. Thus, our results show that including heterozygosity in the model is beneficial for some traits, likely due to dominant gene action.

Fatty acid composition contributes importantly to meat quality and is essential to the nutritional value of the meat. Identification of genetic factors underlying levels of fatty acids can be used to breed for pigs with healthier meat. The aim of this study was to conduct genome-wide association studies (GWAS) to identify QTL regions affecting fatty acid composition in backfat from the pig breeds Duroc and Landrace. Using data from the Axiom porcine 660 K array, we performed GWAS on 454 Duroc and 659 Landrace boars for fatty acid phenotypes measured by near-infrared spectroscopy (NIRS) technology (C16:0, C16:1n-7, C18:0, C18:1n-9, C18:2n-6, C18:3n-3, total saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids). Two QTL regions on SSC4 and SSC14 were identified in Duroc for the de novo synthesized fatty acids traits, whereas one QTL on SSC8 was detected in Landrace for C16:1n-7. The QTL region on SSC14 has been reported in previous studies and a putative causative mutation has been suggested in the promoter region of the SCD gene. Whole genome re-sequencing data was used for genotype imputation and to fine map the SSC14 QTL region in Norwegian Duroc. This effort confirms the location of the QTL on this chromosome as well as suggesting other putative candidate genes in the region. The most significant single nucleotide polymorphisms (SNPs) located on SSC14 explain between 55 and 76% of the genetic variance and between 27 and 54% of the phenotypic variance for the de novo synthesized fatty acid traits in Norwegian Duroc. For the QTL region on SSC8 in Landrace, the most significant SNP explained 19% of the genetic variance and 5% of the phenotypic variance for C16:1n-7. This study confirms a major QTL affecting fatty acid composition on SSC14 in Duroc, which can be used in genetic selection to increase the level of fatty acid desaturation. The SSC14 QTL was not segregating in the Landrace population, but another QTL on SSC8 affecting C16:1n-7 was identified and might be used to increase the level of desaturation in meat products from this breed.

"What is the best strategy to increase the accuracy of genomic selection for meat quality traits?" published on 28 Nov 2015 by Wageningen Academic.

The concentration of omega‐3 fatty acids and selenium (Se) is generally too low in the Western diet. But as the nutrient composition of pork meat and adipose tissue is influenced by the feed given to the animals, the product can be changed to support nutrient demands. Half (297/594) the pigs were given a feed concentrate based on low‐glucosinolate rapeseed products (RS), while the other half was fed a traditional concentrate (Contr): TheRSfeed had an omega‐6/omega‐3 ratio of 3.6:1, and the Contr feed had a ratio of 8.9:1, and both feeds were supplemented with 0.4 mg Se/kg (organic Se: inorganic Se, 1:1). There was a small difference in growth rate, but no differences in feed conversion ratio, lean meat percentage, carcass value, and margin per pig for the two groups. There were no differences in meat quality between the two groups, but there were differences in technological fat quality. TheRSpigs contained about 2 times more alpha‐linolenic acid in the backfat and 41% more in the meat (M. longissimus dorsi) compared to the controls. The concentration ofEPA,DPA, andDHAwere 42% and 20% higher in backfat and meat of theRSpigs compared to the control pigs respectively. The ratio between omega‐6/omega‐3 fatty acids were 4.7 in the meat and 4.0 in the backfat in theRSpigs, and the corresponding values were 6.6 and 8.0 in the control pigs. The selenium content was 0.3 mg/kg meat in both groups. The study showed that a portion of the present pig meat (175 g) provided the daily recommended intake of Se for men and women and about 1/6 of proposed reference intake of omega‐3LCPUFA(250 mg/day) to reduce the risk ofCVDthereby providing a meat that is somewhat healthier for the consumer.