Two experiments were conducted to evaluate the use of intramuscular injections of d-α-tocopherol for control of spontaneous oxidized flavour (SOF) in milk. In exp. 1, 12 mid-lactation dairy cows were either not injected or given an intramuscular injection of 1500 or 3000 IU α-tocopherol on days 1, 8 and 15 of a 29-d experiment. Peak blood plasma and milk α-tocopherol levels were observed 1 and 3 d, respectively, after injection. In plasma there was a quadratic response (P = 0.02) in maximum α-tocopherol concentration to the level of α-tocopherol injected, but in milk the response was linear (P < 0.01). Milk fat concentration increased as level of α-tocopherol injected was increased (P < 0.01). Approximately 5% of the injected dose was excreted in milk over the 7 d following injection. In exp. 2, four commercial farms with a SOF problem in milk were used to test the efficacy of injectable α-tocopherol for control of SOF. Prior to the trial, cows with milk susceptible to oxidation were younger (P = 0.04), were at an earlier stage of lactation (P = 0.03) and tended to give more milk (P = 0.08). All cows were given an oral supplmement of 3000 IU dl-α-tocopheryl acetate per day and half were injected with 3000 IU α-tocopherol. Injection reduced the intensity of oxidized flavour (week 1, P < 0.01; week 2, P = 0.09) and elevated the levels of α-tocopherol in milk for up to 2 wk after injection (P < 0.01). α-Tocopherol injected intramuscularly can increase α-tocopherol levels in milk within 3 d and control milk oxidation. Subsequent oral supplementation can prolong these benefits. Key words: Oxidized milk, tocopherol, flavour, dairy cow
Effects of forage type and extruded linseed supplementation on methane production and milk fatty acid composition of lactating dairy cows