Case study: Differences in milk characteristics between a cow herd transitioning to organic versus milk from a conventional dairy herd

Authors: Tunick, Michael; Van Hekken, Diane; Paul, Moushumi; INGHAM, E - Rodale Institute

Submitted to: International Journal of Dairy Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2015
Publication Date: 10/17/2015
Publication URL: http://handle.nal.usda.gov/10113/62623
Citation: Tunick, M.H., Van Hekken, D.L., Paul, M., Ingham, E. 2015. Case study: Differences in milk characteristics between a cow herd transitioning to organic versus milk from a conventional dairy herd. International Journal of Dairy Technology. 68:511-518. DOI: 10.1111/1471-0307.12255.

Interpretive Summary: Consumers are under the impression that organic milk from cows fed on pasture is better for them than conventional milk. To see how milk changes when cows are switched to organic management, we studied the milk from two adjacent farms. One was a conventional farm with cows fed a mixed ration and never going out to pasture, and the other was undergoing a transition to organic management with cows getting one-third of their energy from fresh pasture. The compositions and kinds of protein were similar in the two types of milk, as were the levels of most of the fatty acids after the first few months. The amount of alpha-linolenic acid, an omega-3 fatty acid, was consistently higher in the transitioning herd milk after a few months. Some levels of volatile flavor compounds varied greatly, and the milk from the transitioning herd was yellower. A transition to organic management results in changes in milk as the cows become accustomed to different feed.

Technical Abstract: Differences between organic and conventional milk were studied by comparing two adjacent farms over a 12-mo period starting at the beginning of the grazing season, thus eliminating variables due to geography and weather. Milk was collected from a farm where cows were fed a conventional total mixed ration with no access to pasture, and from an adjoining farm that was transitioning to organic pasture management (> 30% of dietary energy from pasture during the grazing season). Levels of short- and medium-chain fatty acids partially responsible for aroma and flavor were initially lower in the milk from the transitioning herd, but not after the cows had settled into an organic diet. Once that point was reached, the amount of a-linolenic acid in the transitioning herd milk exceeded that of the conventional herd. The levels of some volatile compounds varied greatly throughout the study. Composition and protein profiles did not differ between the two types of milk. This case study demonstrates that subtle differences occur in the milk as cows transition to organic.