Time-dependent changes in milk fatty acid composition of ewes fed a winter ration supplemented with linseed or sunflower oils

The effects of adding sunflower and linseed oils to a standard winter ration with a lower concentrate content on the milk fatty acid composition in lactating ewes were investigated. Eighteen dairy ewes randomly chosen from the ewe flock were divided into three groups: the first group was fed a winter ration, the second one a winter ration supplemented with sunflower oil, and the third a winter ration supplemented with linseed oil for a period of 12 days. In the treatment groups, the concentrate was partially replaced by 3.0 g/100 g sunflower or linseed oils. Milk samples were taken daily from morning milking for the analysis of fatty acid composition to determine their temporal daily variations. The responses to sunflower oil compared with linseed oil addition after the end of experiment were slightly higher for conjugated linoleic acid (CLA) (P < 0.05), linoleic acid (P < 0.001), trans-10 18:1 (P < 0.001), 6:0 to 16:0 (P approximate to 0.05 - P < 0.001), whereas a higher content of alpha-linolenic acid (ALA) (3-fold) (P < 0.001), oleic acid (P < 0.001), and 18: 0 (P < 0.001) was found in milk after linseed oil addition. The responses to both oil additions were relatively sustainable with regard to CLA, trans-11 18:1 (vaccenic acid, VA), and ALA content after the last 6 days of supplementation. The winter ration supplementation with sunflower or linseed oil led to a 3-fold increase in CLA milk fat content (0.6-2.0 or 1.8 g/100 g fatty acid methyl esters (FAME), P < 0.001) and a 3-fold increase in VA milk fat content (1.2-3.8 or 4.1 g/100 g FAME, P < 0.001), however the content of trans-10 18: 1 was 5-6-fold higher, compared with unsupplemented winter ration. Plant oil supplementation enhanced the total content of CLA, VA, ALA by 5.0 and 3.9 g/100 g FAME (P < 0.001) for linseed and sunflower oil supplementation, and decreased the total content of 12:0, 14:0, and 16:0 by 9.3 and 5.8 g/100 g FAME (P < 0.001) compared to winter diet, respectively.