Transfer of omega-3 linolenic acid and linoleic acid to milk fat from flaxseed or Linola protected with formaldehyde

Four Holstein cows were randomly assigned to four treatments in a 4 × 4 Latin square design. The primary objective of this study was to measure the transfer and increased level of omega-3 fatty acid C18:3 in milk by feeding sup plemental protected fat from flax and, second, to measure the transfer and increase in level of C18:2 by feeding supplemental protected fat from linola. The four dietary treatments were total mixed rations (TMR) plus i) control-no added fat, ii) high levels of protected Linola containing high linoleic acid content, iii) low level of protected flax containing high linoleic acid content and iv) high levels of protected flax containing high linolenic acid content. Linola is a variety of Solin containing approximately 74% linoleic acid, which was developed from flax. These supplements were added to the diet as a top dress and provided 454 g fat (high level) from the protected Linola product, 187 g fat (low level) from the protected flax product and 410 g fat (high level) from the protected flax product. Treatments had no effect on feed intake, milk yield or milk content of fat, protein or solids not fat. Medium chain fatty acids, C12:0 to C16:0, were significantly lower (P < 0.05) in the milk of cows fed supplemental fat. Milk stearic acid (C18:0) was significantly greater in the milk fat from cows fed Linola vs. control, but was unaffected by other dietary treatments. Milk linoleic acid (C18:2) was significantly higher at 10.3% in the milk of cows fed the protected Linola vs. the control at 4.8%. Linolenic acid (C18:3) was not affected by feeding Linola, but was significantly greater in the milk of cows fed the high level of protected flax (6.4% vs. 0.8% in the control). This represents an eightfold increase, while the low level of protected flax diet increased C18:3 by 3.9-fold in milk fat. Supplementing dairy cow diets with a formaldehyde-treated flax product at acceptable levels of fat for high producing cows results in a milk fat high in omega-3-linolenic acid. Key words: Flaxseed, cow, milk, fatty acids, linoleic acid, linolenic acid