635
Feeding Incremental Levels of Ground Flaxseed Increased n-3 Fatty Acids and Conjugated Linoleic Acids in Organically-Managed Jersey Cows
We reported previously that feeding incremental levels of ground flaxseed (GFLAX) linearly reduced DMI, milk production, and contents and yields of milk components. Flaxseed is a high-energy oilseed rich in α-linolenic acid. It is well established the impact of flaxseed on changing milk fatty acids (FA) profile but there is limited research about the effects of GFLAX on milk FA composition, particularly in cows fed high-forage diets. In a recent needs assessment of research and educational needs of the organic dairy industry in the Northeast 84% of respondents indicated the development of value-added dairy products as one of the most pressing areas for dairy research (Pereira et al., 2013 JDS 96:7340-7348), thus justifying additional studies with flaxseed. Twenty organically-managed Jersey cows (425 ± 37 kg of BW and 111± 62 DIM) in the beginning of the study were blocked by milk yield and parity and randomly assigned to treatment sequences in 5 replicated 4 × 4 Latin squares to investigate the effects of incremental levels of GFLAX (0, 5, 10, or 15% diet DM) on milk FA composition. All cows were fed TMR containing (% of diet DM): 55% alfalfa-grass baleage, 8% grass hay, and 37% concentrate; soybean meal (from 6 to 2% of diet DM) and corn meal (from 27 to 16% of diet DM) were replaced with GFLAX (from 0 to 15% of diet DM) while roasted soybean (2% of diet DM) was maintained constant across treatments. Diets were isonitrogenous (mean = 18.3% CP) but crude fat increased from 3.8 to 7.4% when replacing soybean meal and corn meal with GFLAX. Milk concentration (% of total milk FA) of total n-3 FA (0.74 to 1.42%), tC18:1 (1.35 to 2.63%), c9, t11 CLA (0.47 to 0.87%), total CLA (0.55 to 1.08%), total monounsaturated FA (21.9 to 34.3%), and total polyunsaturated FA (2.87 to 4.72%) increased linearly in response to increasing levels of GFLAX. Conversely, milk concentrations of n-6 FA (1.78 to 1.49%) and total saturated FA (72.7 to 58.1%), and the n-6 to n-3 ratio (2.42 to 1.06) declined linearly with increasing levels of GFLAX. Quadratic effects were observed for total n-3 FA, tC18:1, c9, t11 CLA, total CLA, and the n-6 to n-3 ratio. It can be concluded that GFLAX is an effective supplement to enrich milk with bioactive FA of potential health benefits for humans.
Keywords: flaxseed, organic dairy cows, milk fatty acids