SusAn 35 SusPig Sustainability of pig production through improved feed efficiency

Sustainable pig production requires improvements of pigs' efficiency to utilize local feed ingredients The Norwegian pig industry relies on imported feed ingredients, especially soybean meal (SBM), as a protein source in commercial diets. Increased and more efficient use of local protein sources, such as rapeseed meal (RSM), holds the potential to improve the sustainability and self-sufficiency of local pig production. Use of RSM in pig diets is, however, often associated with reduced feed intake, growth rate, and nutrient utilization due to the high fiber content and the presence of anti-nutritional factors, including glucosinolates. Consequently, further improvements in sustainable pig production require development of new breeding strategies to adapt existing pig genotypes to novel fiber-rich diets. To evaluate differences among pigs in their ability to utilize fiber-rich feed resources, a trial was carried out with 84 Norwegian Landrace pigs fed an SBM-based control diet or an RSM-based test diet. The RSM-fed pigs had a higher feed conversion ratio (FCR) compared to pigs fed the SBM diet (2.34 vs. 2.29). There was large individual variation in FCR between pigs, ranging from 1.99 to 2.60. Further, our results showed large individual variation in traits affecting feed efficiency (FE), such as in pigs' ability to digest nutrients. The large variation in FE and nutrient digestibility demonstrates that some pigs can better utilize a fiber-rich diet, and hence they are able to maintain production efficiency. To gain a deeper understanding of the differences in metabolism and utilization of the diets by the pigs, we have performed gene expression analyses of samples from gut, muscle and liver and analyses of blood hormones that regulate appetite (peptide YY (PYY), glucagon, and cholecystokinin (CCK)) and thyroid function (triiodothyronine (T3) and thyroxine (T4)). We have identified several differently expressed genes (DEGs) in ileum, colon, liver, and muscle from pigs showing high and low FE when fed the two diets. The highest number of DEGs were observed in ileum, whereas only 5 genes were differently expressed in the liver of pigs with high FCR vs pigs with low FCR. In the ileum we observed 1838 down-regulated genes and 1573 upregulated genes in the less efficient pigs as compared to the more efficient pigs. In the colon, we observed 485 down-regulated genes and 377 upregulated genes in the less efficient pigs (i.e. high FCR) as compared to the more efficient pigs. The pathways and function of these DEGs are now being evaluated. In muscle, although small, the detected differences in gene expression patterns between pigs fed SBM or RSM diets provided valuable molecular explanations for observed differences in growth performance. RNA sequencing data revealed differential regulation of key genes involved in carbohydrate, lipid and energy metabolism, muscle tissue development, mitochondrial function, and oxidative stress between the diets. The results suggested activation of growth suppressive signaling and atrophy in the skeletal muscle of pigs fed RSM compared to SBM. Reduced growth of RSM pigs was accompanied by the activation of several genes orchestrating adaptive gene expression responses, including the changes in energy metabolism and muscle tissue remodeling. Some of the differentially expressed genes between the RSM and the SBM pigs may be the key contributors to variation in measured growth performance traits, thus having a potential to serve as biomarkers for FE. Results from the hormone analysis showed that the concentration of PYY, CCK and glucagon were higher in the control pigs than those fed the local diet, suggesting differences in regulating appetite and feed intake between the groups. However, feed intake and growth rate were also higher in these pigs. This could be associated with the higher fiber and glucosinolate level in the RSM diet which has a negative effect on feed intake. Also, the concentration of the thyroid hormones T3 and T4 was higher for the control pigs. These hormones play central roles in regulating eating behavior and appetite in the animals. A report from this study is under development. To evaluate how well pigs performed when fed a local high-fiber RSM- and field bean-based diet, and how this local diet affected the meat quality of the pork, another study was carried out with Norwegian crossbred growing-finishing pigs. Pigs fed the local diet had similar feed intake, growth rates and carcass quality as those fed the imported SBM diet. Feeding the local diet also improved the quality of the meat. The meat was juicier with a fresher color and taste and with a longer shelf-life. The improved quality of the meat was associated with a reduced level of pyroglutamic acid and increased levels of free amino acids and sweet tasting metabolites in the meat. These results were published in Meat Science in 2020.

The project has evaluated feed efficiency (FE) of pigs fed fiber-rich local diets based on rapeseed meal and field beans. Phenotypic biomarkers based on gene expression analysis, activity of digestive enzymes and hormones regulating appetite have been identified. Pigs fed fiber-rich diets had high performance, a healthier gut microbiota profile and pork with improved quality. Outcomes: Several peer reviewed publications, presentations to stakeholders both on a national and international level, and training of young scientists. We hope to identify phenotypic biomarkers based on gene expression, digestive enzymes and hormone analyses of samples from pigs fed the conventional and local fiber-rich diets. These can help us identify novel phenotypes and biomarkers associated with FE traits that can help explain differences in FE in pigs and that can be used in future breeding programs. Whether this variation is heritable should be estimated in field trials with larger numbers of pigs.

Sustainable pig production is characterized by economic profitability through improved productive output, while maintaining animal health and welfare, and without compromising environmental resources. This study aims to enhance sustainability of European pig production through improved feed efficiency (FE) at different scales. The supporting objectives are to 1) Evaluate the consequence of improved FE for fitness, to improve animal robustness; 2) Evaluate if improved FE can be sustained with more reliance on local feed resources and feedstuff co-products; 3) Evaluate the environmental, social and economic impact of improved FE on local feed resources and feedstuff co-products; and 4) To develop future sustainable pig production systems. We approach this by: 1) Evaluation of robustness traits in experimental and commercial pigs; 2) Evaluation of FE and robustness in response to feedstuff co-products and local pig diets; 3) Assessment of the environmental and social impact of pig production as enhanced by transforming low quality feed, through Life Cycle Assessment (LCA) analysis; and 4) Modelling of future sustainable production systems. This project combines the expertise of European research groups in cooperation with those from the USA and Australia through a multidisciplinary approach. The work is relevant to Research Area 1: FE affects profitability of animal production through reduced feed costs, but economic benefits are also directly influenced by animal robustness. Efficient use of local resources may improve the productivity, resilience and competitiveness of European pig production; Research Area 2: Improving FE of pigs in transforming low quality feed may improve local resource use and enhance the environmental sustainability of European pig production; Research Area 3: Understanding the implications of improving FE on animal robustness may improve animal welfare, breeding strategies and consumer acceptance of pig production and breeding practices.