Lucerne protein for organic pigs
Lucerne harvested as forage can produce two- to three-fold the protein yield of pulses grown in Denmark. Efficient extraction of protein from lucerne may unlock ways for more self-sufficient production of pigs in organic farming.
Lucerne is known as a valuable feed for dairy cows. New processing methods may increase the value of lucerne exceedingly by extracting proteins for pig feed and at the same time providing a fibre-rich fraction as feed for ruminants. The ProRefine project aims to gain new knowledge about how to fractionate lucerne and evaluate the effects on feed value. The processing methods we are testing in the CORE Organic Cofund project are leaf stripping and juice pressing, resulting in fractions of leaves, stems, juice and pulp. Different prototypes of leaf strippers have been developed by TRUST’ING & ALF’ING, a project partner in France.
Lucerne harvesting in Denmark
Lucerne was harvested and processed into four fractions at Aarhus University in Denmark 21-22 May 2019. The plants were in early bud stage with a mean canopy height of 57 cm and the estimated yield was 3 tonnes of dry matter per hectare. The leaf fraction accounted for roughly one third and the stems fraction for two thirds of the yield. In the press screw treatment, the protein paste accounted for one tenth, the pulp for half and brown juice, that may be utilised in a biogas plant, for the rest of the yield.
Leaves were ensiled together with crushed barley grains, stems were ensiled without additives, the juice was heated to precipitate a protein paste that was subsequently frozen, and the pulp was ensiled without additives. In autumn 2019, the project partners INRA in France and UNICATT in Italy will assess the feeding value of these feeds in experiments with pigs (leaves and protein paste) and sheep (stems and pulp).
Benefits of fractionating forage legumes
What is the potential impact of implementing fractionation of lucerne in organic pig production? For pigs, protein concentration, amino acid composition, digestibility and eventual antinutritional factors define the feed value and the maximum inclusion level in the diet. If we assume that a slaughter pig (finisher weight 85 kg) consumes a total of 180 kg of feed on a dry matter basis with an average protein content of 15 percent, the total protein consumption will be 27 kg.
Furthermore, we assume that half of the feed protein can be covered by green protein from lucerne, either in the form of leaves or protein paste. With a forage yield of 3 tonnes per hectare at the first cut, a protein content of 21.8 percent, and a 50 percent recovery of the protein in the leaf or protein paste fraction, the first cut of one hectare can contribute 330 kg of protein that can be fed to pigs. Consequently, the first cut of one hectare of lucerne in Denmark could cover half of the protein requirement of approximately 24 slaughter pigs. In addition, approximately 2 tonnes of ensiled stems per ha or 1.5 tonnes of pulp (on a dry matter basis) can be fed to dairy cows. However, there are many factors that can lead to reduced yields, lower inclusion levels or lower feed values than anticipated.
ProRefine will study some of these factors and even perform a sustainability assessment. Field trials in different regions in Europe and Turkey will contribute with additional results. In addition to lucerne we will also study two other forage legumes, red clover and alsike clover.
Authors
Lene Stødkilde-Jørgensen, Aarhus University, Denmark, lsj@anis.au.dk
Søren Krogh Jensen, Aarhus University, Denmark, skj@anis.au.dk
Steffen Adler, Norwegian Institute of Bioeconomy Research, steffen.adler@nibio.no
