Variations in the quality of butter, particularly in relation to the vitamin A, carotene and xanthophyll content as influenced by feeding artificially dried grass to stall-fed cattle

Oxycarotenoids in Poultry Feeds

“…Lutein is a constant component of milk and butter (317), where it varies in concentration depending on the amount of green feeds fed. It has also been found in the serum of cattle (314) but not in the body fat of cattle.…”

Carotenoid vitamin A precursors and analogs in foods and feeds

“…Since the dairy cow has a variable carotene intake over the year, as influenced by alternate feeding of fresh pasture and dry roughage and feed, the /3-carotene and vitamin A content of the milk fluctuates accordingly (78,195,225).…”

Determination of Vitamin A and Carotene in Milk. A Rapid Extraction Procedure

“…importance of milk as a source of vitamin A makes a rapid and accurate method for the determination of vitamin A and carotene in milk desirable. Earlier procedures which involved butterfat as a starting material (2,5) were improved by Wilkie (13) and Olson et al (11) by the use of direct extraction procedures based on a modification of the Roese-Gottlieb method (1) for the determination of fat in milk. Willstaedt and With (14) and Chevallier and Manuel (3) used an ether extraction of milk after incubation for 2 days with aqueous potassium hydroxide.…”