POULTRY FACT SHEET NO. 21
UNIVERSITY OF CALIFORNIA
THE USE OF FLAXSEED AS A POULTRY FEEDSTUFF
F.H. Kratzer and Pran Vohra University of California, Avian Sciences Department, Davis, CA 95616
Flax or linseed (Linum usitatissimum L.) is grown in the northern United States and southern Canada. It is a source of linseed oil, an important drying oil for paints, varnishes and linoleum. Flaxseed may be processed by mechanical expellers or solvent extraction and the residual linseed meal is available as an animal feed ingredient. Linseed meal is an important feedstuff for cattle but its use in poultry feeds is limited.
Flaxseed contains a cyanide containing glucoside, linamarin, which releases hydrogen cyanide under acidic, moist conditions in the presence of an enzyme, linase. Under normal processing conditions involving high temperature treatment, linase is destroyed so that the subsequent release of hydrogen cyanide is not a problem.
Flaxseed contains about 34% oil which is reduced to about 5% by expeller processing or about 1% by solvent extraction (Table 1). The fiber content of the meal is relatively high, but in addition, contains mucilage, a water-dispersable polysaccharide which is extremely sticky when wet. The protein of linseed meal is somewhat deficient in lysine, and possibly, methionine.
Historically, linseed meal has not been a satisfactory feedstuff for poultry. It could satisfactorily replace the protein equivalent of soybean meal up to 2 or 3 percent of the diet, but higher levels caused noticeable reduction in gain and feed efficiency in broilers and poults (Ewing, 1963). The adverse effect of feeding linseed meal was greater than one would predict from the nutritional contribution to the diet and there was concern that it contained a toxic factor. At one time, it was speculated that cyanide from its cyanogenetic glucoside might be responsible for the adverse feeding value.
Table 1. Composition of flaxseed, expeller linseed meal and solvent extracted linseed meal. --------------------------------------------------------------------- Flaxseed Expeller Solvent Linseed Linseed Extracted Meal Linseed Meal --------------------------------------------------------------------- Crude protein, % 22.0 34.3 34.6 Fat, % 34.0 5.4 1.4 Crude fiber, % 6.5 8.8 9.1 ME, Kcal/kg 3957 2350 2097 Methionine, % 0.35 0.58 0.54 Cystine, % 0.42 0.61 0.61 Lysine, % 0.92 1.18 1.16 Tryptophan, % 0.22 0.50 0.51 Threonine, % 0.77 1.14 1.22 Isoleucine, % 0.95 1.69 1.68 Histidine, % 0.44 0.65 0.69 Valine, % 1.17 1.61 1.74 Leucine, % 1.25 1.92 2.02 Arginine, % 2.05 2.81 2.94 Phenylalanine, % 0.97 1.38 1.46 Tyrosine, % 0.59 0.96 1.09 Glycine, % 1.34 1.63 1.74 Serine, % 1.14 1.89 1.92 Vitamin E, mg/kg 18.9 8.0 14.0 Thiamin, mg/kg 7.0 4.2 7.5 Riboflavin, mg/kg 4.5 3.2 2.9 Pantothenic acid, mg/kg 14.3 14.7 Folic acid, mg/kg 2.8 1.3 Pyridoxine, mg/kg 5.5 3.3 Niacin, mg/kg 41.0 37.0 33.0 Choline, mg/kg 3150 1780 1393 Calcium, % 0.25 0.41 0.39 Phosphorus, % 0.50 0.87 0.80 Sodium, % 0.08 0.11 0.14 Potassium, % 1.50 1.22 1.38 Magnesium, % 0.50 0.58 0.60 Manganese, mg/kg 38 38 Iron, mg/kg 236 176 319 Copper, mg/kg 22.0 26.0 26.0 Zinc, mg/kg 91 33 88 Linoleic acid, % 5.1 0.81 0.21 Linolenic acid, % 17.7 2.81 0.73 --------------------------------------------------------------------- (From Raw Material Compendium, Novus, 1994; Barbour and Sim, 1991)
Kratzer (1946) and McGinnis and Polis (1946) reported that the growth of chicks fed linseed meal could be greatly improved if the meal were treated with water and dried before being mixed in the feed. The response was unrelated to the cyanide contained in the meal. Extraction with 50% ethanol was beneficial, but the extract was not detrimental. In further studies, it was found that supplementation of a diet containing 30% linseed meal with a yeast extract caused an improvement in growth and a vitamin mixture could also be beneficial (Kratzer and Williams, 1948). The vitamin in the mixture which was responsible for the growth improvement was pyridoxine, although the unsupplemented diet contained far more of the vitamin than the requirement in a conventional diet (Kratzer and Williams, 1948). Poults showed a growth response to the water treatment of linseed meal and its supplementation with pyridoxine in the same manner as chicks (Kratzer, 1949). Maximum growth of chicks was obtained with the addition of 7 milligrams of pyroxidine per kilogram of diet. Much work was done to identify the apparent pyridoxine antagonist, until its final resolution was made by Klosterman et al. (1967) in the identification of linatine. Linatine is gamma-glutamyl-1-amino-D-proline which can be hydrolytically cleaved to glutamic acid and 1-amino-D-proline. The latter forms a stable complex with pyridoxalphosphate, which presumably induces a pyridoxine deficiency.
Studies with water-treated linseed meal as the only protein source in a diet for chicks showed that the major amino acid deficiency was that of lysine (Kratzer et al., 1947). It was interesting that the growth of chicks fed the amino acid supplemented linseed meal was as good as that of chicks fed a conventional control diet, even though the mucilage caused sticky droppings. Wylie et al. (1972) supplemented starter rations with 26 mg of pyridoxine per kg and growing rations with 6 mg pyridoxine per kg. and found that linseed meal could be used satisfactorily at 17 to 18% of the diet and could replace half of the soybean meal in the ration for starting and growing pullets. Madhusudhan et al. (1986) successfully used water-treated linseed meal to supply 50 to 75% of the protein in a diet for chickens. Untreated linseed meal at 20% of the diet was distinctly inferior.
Linseed oil is highly unsaturated. It is rich in linolenic acid (Table 2) which contains 3 double bonds with its first double bond 3 carbons from the terminal end (omega-3). The beneficial effects of consuming omega-3 fatty acids from fish include reducing heart disease, reducing circulating cholesterol levels and suppressing inflammation in humans (Klatt, 1986). This has prompted studies on the effect of feeding linseed oil or feedstuffs containing it to poultry as a means of increasing linolenic acid in eggs and poultry meat. As early as 1950, Chu and Kummerow reported that feeding a high level (25%) of linseed oil to chickens caused increased linolenic acid in the fat of the skin and gizzard. Kummerow et al. (1948) also reported that feeding linseed oil to turkeys increased the iodine number of the fat and it was less stable to oxidation. Klose et al. (1952) showed that including 2% of linseed oil in a turkey ration caused a large increase in the linolenic acid in the depot fat, a marked reduction in the induction period for fat oxidation and a marked fishy odor of the tissue.
Table 2. Fatty acid composition of linseed, soybean and corn oils (Percent of total fatty acids) ------------------------------------------------------------------- Fatty Acid Linseed Soybean Corn Oil Oil Oil ------------------------------------------------------------------- Palmitic (C-16:0) 6 11 12 Stearic (C-18:0) 4 4 1 Oleic (C-18:1) 22 27 25 Linoleic (C-18:2) 15 50 60 Linolenic (C-18:3) 52 7 1 -------------------------------------------------------------------
The effect of linseed oil on fatty acid composition in broiler chickens has been studied at 56 days of age by Phetteplace and Watkins (1989) and for shorter periods by Olomu and Baracos (1991). Linseed oil fed at from 1.5% to 5% increased the incorporation of omega-3 fatty acids into chicken muscle lipids with the longer chain fatty acids influenced less than linolenic acid. While there was an increase in the omega-3 fatty acids, there was a slight decrease in the long chain omega-6 fatty acids. This may be due to competition of fatty acids resulting in decreased activity of the delta-6-desaturase enzyme. There are other effects of the omega-3 fatty acids upon fatty acid metabolism which are not completely understood.
In 1990, Caston and Leeson reported on feeding 10, 20 and 30% flaxseed to laying hens for a 28-day period and collecting eggs for analysis in the last 3 days of the period. There were large increases in omega-3 fatty acids in the eggs at all levels of flax seed supplementation. Cheronian and Sim (1991) fed flax seed to laying hens at 8 and 16% in diets which were supplemented with pyridoxine. They reported increased omega-3 fatty acids in the eggs, and brain tissue of embryos and chicks from the hens fed the ground flaxseed. The increase in linolenic acid in eggs from hens fed flax seed was mainly in the triglycerides. The longer chain omega-3 fatty acids were deposited exclusively in the phospholipids (Jiang et al., 1991). The fatty acid composition of chicks was significantly altered by egg yolk lipids. The percentage incorporation of omega-3 fatty acids into the chick, however, increased when the yolk sources of these fatty acids were low. There is evidence that elongation of omega-3 fatty acids occurs during incubation (Cherian and Sim, 1993).
Jiang et al. (1992) reported that about 36% of the sensory evaluations reported a fishy or fish-related flavor in the eggs from hens fed flaxseed. This was not noted in eggs from hens fed the control diet or diets containing high oleic acid or high linoleic acid sunflower seeds. Aymond and Van Elswyk (1995) reported that feeding both 5% and 15% flaxseed caused increased total omega-3 fatty acids in the eggs and that the ground seeds caused a greater level of these fatty acids at the 15% level of feeding than the whole seed. Yolk thiobarbituric acid reactive substances, a measure of rancidity, were not influenced by feeding flaxseed up to the 15% level. Feeding 3% of linolenic acid to hens increased the omega-3 fatty acids in the total lipids of the eggs and there were no differences in the lipid deposition in 7 strains of chickens which were tested (Ahn et al., 1995). The flavor scores of eggs from the control group were more favorable than those of the enriched eggs, but the differences were not great.
Farrell (1995) studied human volunteers who consumed ordinary eggs or omega-3 enriched eggs at a rate of 7 eggs per week. After 20 weeks, the plasma levels of omega-3 fatty acids in volunteers consuming the enriched eggs were significantly higher than in those consuming the ordinary eggs and the ratio of omega-6 to omega-3 fatty acids was reduced. There were only small differences in the plasma cholesterol. He concluded that an enriched egg could supply approximately 40-50% of the daily requirement for omega-3 polyunsaturated fatty acids. In a Texas study (Marshall et al., 1994), it was found that 65% of the consumers surveyed reported a willingness to purchase omega-3 enriched eggs, and of that number, 71% would be willing to pay an additional $.50 per dozen.
Linseed meal may be used satisfactorily as a protein supplement for poultry if it is water-treated or supplemented with pyridoxine to counteract the pryidoxine antimetabolite. The protein is somewhat deficient in lysine and must be properly supplemented. The mucilage of the linseed meal causes sticky droppings, but this does not affect the performance of the birds.
Linseed oil is a rich source of linolenic acid which can be incorporated into the meat and eggs of birds to which it is fed. The total omega-3 fatty acids are increased in these poultry products, however, there is some evidence that a fish flavor may result. The health benefits and the cost effectiveness of producing and consuming omega-3 enriched eggs is still under investigation.
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