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Linum usitatissimumFlax, linseedUseful reference: 237 An annual, 0.3-1 m high, grown for the production of fibre and flaxseed or linseed oil - a drying oil used in paints, linoleum and soft soap. From one to ten seeds are found in each of the round balls at the tips of the branches. The term linseed meal is used for ground unextracted seed, for ground linseed cake and for meal from the extraction process; each having a different oil content (35%, 10% and 3% respectively). As the oil content largely determines the use of linseed meal, it is necessary to know which specific product is meant by the term. The hull is low in fibre and rich in protein and is therefore included in the oilcake. PRUSSIC ACID. Immature linseed contains the glucoside linamarin. At certain temperatures (optimum 40 -50 C), conditions of acidity (pH 2-8) and in the presence of moisture, an associated enzyme linase - will release prussic acid from the glucoside. Under normal conditions of manufacture, involving high-temperature treatment, the linease is destroyed so that no prussic acid can subsequently be released. Unprocessed whole seeds and linseed cakes processed under low temperature can be toxic to animals, especially if the seed or the cake is wetted before being used for feed. As the enzyme is destroyed by sufficient heat, boiling for ten minutes will make the feed safe. Extraction with trichloroethylene or carbon tetrachloride destroys the glucoside. SEED. The whole seed is too hard for animal feeding and must be either crushed or softened by soaking and boiling. Because it is rich in oil it can be used as a concentrated energy feed for ruminants and pigs. Whole seeds can be used as an ingredient in calf meals. As the oil in the seed is unsaturated, it may produce soft pork if too much seed is fed to pigs. OILCAKE. Linseed cake has the reputation of causing "bloom" on the coats of cattle, which is attributed to the oil. The cake in large amounts is laxative, and an excess has an undesirable softening effect on the butterfat and gives the milk a rancid taste. The recommended maximum intake for cattle is 3 kg per day. Because of this softening property of the oil, linseed cake is unsatisfactory as a main ingredient in pig feeds. Moreover, being deficient in some essential amino acids, it is not suitable as the sole source of proteins for swine. It is, however, a good protein supplement when used together with fish meal, skim milk or other animal by- products. Of course, the extracted meal is not likely to have any softening effects. Up to 1 kg per day has been used with good results, but not more than 8% linseed meal is commonly included in rations. For young pigs and brood sows, a maximum of 5% linseed meal in the ration is usually recommended. Linseed cake is toxic to poultry except in very small proportions (under 3%). Larger amounts depress growth. The toxicity can largely be eliminated by soaking the meal in water for twenty-four hours or by adding pyridoxin, one of the B-vitamins, to the diet. The reasons for the antitoxic effect of the vitamin are unknown.
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