During the past few years a large amount of butter manufactured in the Middle West has been criticised for weedy flavors. This increase in weedy flavors unquestionably has resulted from a number of successive dry years. Some of the most common weed defects in this section are wild onion (Allium cernuum) , ragweed (Ambrosia artemisiifolia L.) and dog fennel (Anthemis cotula L.). The defects resulting from skunk cabbage (Symplocarpus foetidus (L.)), french weed (Thalaspi arvense L.) and peppergrass (Lepidium verginicum L.) (2) are apparently less common.
Feed flavors are more important than weed flavors in this section. It has been recognized for some time that silage and alfalfa hay, when fed to dairy herds in fairly large quantities, cause definite milk flavors that are apparent in the butter. Changes in feeding procedures designed to lower fat production costs have, in many cases, increased the problems of the buttermaker. Sweet clover, rye pasture, wheat pasture, soybean hay and cane silage, flavor milk to such an extent that they affect the quality of the resulting butter.
Fabricius, N. E. and Bird, E. W.
"The quality of butter made from Vacuum-pasteurized and Vat-pasteurized lots of the same creams,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 25
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol25/iss284/1