The production of milk rich in alpha-linolenic acid by feeding a large amount of linseed to cows

To produce milk rich in alpha-linolenic acid (C18 3(n-3)), an experiment (Expt) 1 was conducted with a switch-back trial, each for a 14-day experimental period, using four lactating Holstein cows given a diet containing linseed. Each day, the cows were fed a control diet containing 11.3g of C 18:3(n-3) (Diet 1) or an experimental diet containing 344.1g of C 18:3(n-3) (Diet 2), which included approximately 2.0kg (dry waiter (DM) basis) of linseed. Experiments 2 and 3 were conducted using four cows each, with half the cows fed an experimental diet each day containing 734.9 or 825.6g of C 18:3(n-3) (Diet 4 or Diet 6) for a period of 56 days, and the remaining half received a dally control diet containing 37.3 or 74.5g of C 18:3(8-n) (Diet 3 or Diet 5). The cows given Diets 4 and 6 dally received approximately 3.4 and 3.8kg (DM basis) of linseed. respectively. Fatty acid (FA) profiles of fat in feeds, serum lipid and milk fat were obtained through a gas-chromatograph analysis. The C 18:3(n-3) content of the serum lipids of the cows given Diet 2 significantly increased, whereas the linoleic acid (C l8:2(n-6)) content significantly decreased compared with those of the cows given Diet 1. The C 18:3(n-3) content of the serum lipids of the cows given Diet 4 increased from 4.27 to 20.35%, whereas the C 18:2(n-6) content decreased from 44.74 to 27.99%. The cows given Diet 6 showed similar results. The C 18:3(n-3) was predominant in the serum lipids, but its level was only approximately 0.4% of the total milk FA for the control cows. The C 18:3(3-n) content in the milk fat increased slightly when the cows received Diet 2, but it rose to more than 1.0% when the cows received Diet 4 or Diet 6. and was maintained throughout the feeding of the diets When the cows received Diets 1. 2. 3, 4. 5 and 6. the efficiencies of transfer of C 18 : 3(n-3) into milk fat were 13.2, 0.7, 7.4, 1.7, 5.1 and 1.0%. respectively