Refining life cycle nutrient modeling in organic pig production. An analysis focusing on feeding strategies in organic Danish pig farming

Abstract

Organic pig farming systems are associated with considerable ammonia losses, nitrate leaching in sow pasture concepts, and dependency on imported protein feed components, such as soybean cake. Furthermore, in environmental nutrient modeling approaches, there is a lack of data on emission factors and models that account for nutrient balances concerning organic production systems. Therefore, the present study aimed to analyze feeding strategies in organic pig farming by using refined nutrient modeling approaches.A cradle-to-farm-gate life cycle approach was used to analyze six feeding scenarios: reduced crude protein content in feed rations for sows (S1) and sows and fattening pigs (S3), alternative protein sources and reduced protein in feed rations for sows (S2) and sows and fattening pigs (S4), and reduced compound feed intake for sows (S5) and sows and fattening pigs (S6). Danish average production data were collected and specific data regarding organic production (N content in manure, emission factors for ammonia for the paddock and housing) were identified. Six sub-systems (paddocks with sows and piglets on grass-clover, weaners, fattening pigs, feed, manure, and manufacturing of inputs) were considered and balanced out. Five environmental impact categories, climate change (including soil carbon changes), eutrophication potential, acidification potential, abiotic depletion of fossil fuels, and land occupation, were assessed.It was found that the feeding strategies had considerably higher effects when including both sows and fattening pigs compared to only including sows. The highest reductions for most of the analyzed environmental impacts (13% for eutrophication and acidification, 11% for climate change, and 8% for land occupation) were estimated due to reduced amount of compound feed to both sows and fattening pigs (S6). For abiotic depletion of fossil fuels, a decrease of 33% was determined by the use of locally grown protein sources (S4), which decreased the contribution of transportation. In terms of methodological refinements, an approach for nutrient modeling at the paddock level, where crop rotation and associated effects were also considered, was identified. Furthermore, adapted emission factors for indoor housing with access to outdoor runs were suggested.