The consequences of using home grown protein sources in pig diets
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Research partners: SAC
Sponsors: BPEX
Duration: October 2007 – January 2010
The UK pig feeding industry relies heavily on imported protein feedstuffs, primarily soybean meal. Whilst soybean meal has an excellent nutritive value for pigs, there are growing concerns about the environmental impact of its use, particularly in relation to long transport distances. The overall aim of this study is to simulate, at farm level, the environmental impacts of replacing soybean meal with home-grown legumes (peas, beans or lupins) in starter, grower and finisher pig diets.
A life cycle assessment framework to assess the environmental impacts of pork production from starter to slaughter weight has been developed on the basis of current industry diet specifications for each growth stage. The framework consists of eight sub-models, the two main models are:
1) The Pig Growth model which determines nutritional requirements, daily feed intake and nitrogen excretion
2) The DeNitrification DeComposition Crop model which simulates the environmental impacts of crop growth for dietary ingredient production.
The final environmental impacts include the consequences of all processes/activities involved in the crop and pig production processes.
Environmental impacts are quantified as Global Warming Potential (GWP, expressed in terms of kg CO2 equivalent100), Acidification (expressed in kg SO2 equivalent) and Eutrophication (expressed in kg PO4 equivalent) per kilogram pig (the functional unit). These impacts were simulated for two UK sites with large pig populations (East Anglia and Yorkshire), and comparisons have been made between three soil types. The average acidification and eutrophication potential associated with the production of a kilogram of pig is lower for pigs that are fed on diets based on home-grown proteins than on soya based diets, mainly because of the long transport distances associated with soybean meal. This was, however, not necessarily the case for the GWP as a result of considerable variation in greenhouse gas release associated with the production of dietary ingredients as a function of variation in soil characteristics and weather conditions during crop growth.
An increased use of home-grown legumes in UK pig diets lowers the eutrophication and acidification potential when compared with the inclusion of soya used primarily as dietary protein. Additional economical benefits may arise from reduced dependency on imported feedstuffs. Environmental benefits may also be gained if UK legume varieties could be modified to increase yields per hectare and by optimising the growth conditions of all crops, which could potentially lower the GWP associated with the production of a dietary ingredients.
Page last updated 08 June 2010