Oil seed by-products as alternative protein sources for imported protein-rich feed

The protein-rich, solvent-extracted meals and press cakes of oilseeds are among the most important protein sources used in compound feed worldwide. In Switzerland, 85 % of oil seed by-products have to be imported. Rapeseed and sunflowers are the most important indigenous oilseeds. Domestic production is bound to contractually negotiated quantities and has thus limited expansion potential. Crude protein, fibre and energy content of especially sunflower by-products deviate, depending on hull proportion, substantially from the ideal profile. However, protein from rapeseed and sunflower is a good source for S-containing amino acids and in this respect superior to soy protein. Sunflower by-products are deficient in lysine for demanding animals and the partially dehulled and non-dehulled commercial grades contain too little energy for monogastric animals. In addition, the high oleic acid varieties cause high PUI indices, which is undesired in diets for fattening pigs for fat quality reasons. Among the minor oilseeds, the press cake of the oil pumpkin stands out with a crude protein content of over 550 g/kg DM together with a high nutrient digestibility, which makes it a multi-purpose protein source. However, the protein quality does not quite match the ideal profile. The high residual fat content will limit its use in diets for fattening pigs, which in principle applies to all press cakes. As hardy crops, linseed and camelina are well suited for low-input production systems. The nutrient profile and antinutritive compounds in the by-products limit their use in the feed of monogastric animals, which can be improved by thermal treatment. Due to low protein yield per ha of domestic oilseeds, too much arable land would be used at the expense of other crops to substantially increase the national protein supply.

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