Potentials to differentiate milk composition by different feeding strategies

Summary

To investigate the effect of the dietary intake of the cow on milk composition, bulk-tank milk was collected on 5 occasions from conventional (n = 15) and organic (n = 10) farms in Denmark and on 4 occasions from low-input nonorganic farms in the United Kingdom, along with management and production parameters. Production of milk based on feeding a high intake of cereals, pasture, and grass silage resulted in milk with a high concentration of α-linolenic acid (9.4 ± 0.2 mg/ kg of fatty acids), polyunsaturated fatty acids (3.66 ± 0.07 mg/kg of fatty acids), and natural stereoisomer of α-tocopherol (RRR-α-tocopherol, 18.6 ± 0.5 mg/kg of milk fat). A milk production system using a high proportion of maize silage, by-products, and commercial concentrate mix was associated with milk with high concentrations of linoleic acid (LA; 19.7 ± 0.4 g/kg of fatty acids), monounsaturated fatty acids (27.5 ± 0.3 mg/kg of fatty acids), and a high ratio between LA and α-linolenic acid (4.7 ± 0.2). Comparing these 2 production systems with a very extensive nonorganic milk production system relying on pasture as almost the sole feed (95 ± 4% dry matter intake), it was found that the concentrations of conjugated LA (cis-9,trans-11; 17.5 ± 0.7 g/kg of fatty acids), trans-11-vaccenic acid (37 ± 2 g/kg of fatty acids), and monounsaturated fatty acids (30.4 ± 0.6 g/kg of fatty acids) were higher in the extensively produced milk together with the concentration of antioxidants; total α-tocopherol (32.0 ± 0.8 mg/kg of milk fat), RRR-α-tocopherol (30.2 ± 0.8 mg/kg of milk fat), and β-carotene (9.3 ± 0.5 mg/kg of milk fat) compared with the organic and conventional milk.
Moreover, the concentration of LA (9.2 ± 0.7 g/kg of fatty acids) in milk from the extensive milk production system was found to approach the recommended unity ratio between n-6 and n-3, although extensive milk production also resulted in a lower daily milk yield.