Fat composition of organic and conventional retail milk in northeast England

Abstract

This study of UK retail milk identified highly significant variations in fat composition. The survey, conducted over 2 yr replicating summer and winter, sampled 22 brands, 10 of which indicated organic production systems. Results corroborate earlier farm-based findings considering fat composition of milk produced under conventional and organic management. Organic milk had higher concentrations of beneficial fatty acids (FA) than conventional milk, including total polyunsaturated fatty acids (PUFA; 39.4 vs. 31.8 g/kg of total FA), conjugated linoleic acid cis-9,trans-11 (CLA9; 7.4 v 5.6 g/kg of FA), and α-linolenic acid (α-LN; 6.9 vs. 4.4 g/kg of FA). As expected, purchase season had a strong effect on fat composition: compared with milk purchased in winter, summer milk had a lower concentration of saturated fatty acids (682 vs. 725 g/kg of FA) and higher concentrations of PUFA (37.6 vs. 32.8 g/kg of FA), CLA9 (8.1 vs. 4.7 g/kg of FA), and α-LN (6.5 vs. 4.6 g/kg of FA). Differences identified between sampling years were more surprising: compared with that in yr 2, milk purchased in year 1 had higher concentrations of PUFA (37.5 vs. 32.9 g/kg of FA), α-LN (6.0 vs. 5.1 g/kg of FA), and linoleic acid (19.9 vs. 17.5 g/kg of FA) and lower concentrations of C16:0 and C14:0 (332 vs. 357 and 110 vs. 118 g/kg of FA, respectively). Strong interactions were identified between management and season as well as between season and year of the study. As in the earlier farm studies, differences in fat composition between systems were greater for summer compared with winter milk. Large between-year differences may be due to changes in weather influencing milk composition through forage availability, quality, and intake. If climate change predictions materialize, both forage and dairy management may have to adapt to maintain current milk quality. Considerable variation existed in milk fat composition between brands.

Improving the fatty acid profile of winter milk from housed cows with contrasting feeding regimes by oilseed supplementation

“…This suggested that the addition of between 1.6 and 2.1 kg of rolled oilseeds/cow per day to winter diets for conventional and organic cows, as in this study, would not affect milk production or total solids; the two parameters dairy producers are currently paid for. Across the experiments and production systems, linseed supplementation of silage diets during winter housing: (a) decreased the milk concentrations of SFA, C12:0, C14:0 and C16:0 and (b) increased milk concentrations of a range of nutritionally desirable FA (including MUFA, OA, VA, PUFA, n-3, ALA and RA) and the n-3/n-6 ratio, to levels similar to or higher than those found in milk from grazing (Butler et al, 2008(Butler et al, , 2011, being in line with previous studies (Akraim, Nicot, Juaneda, & Enjalbert, 2007;Collomb et al, 2004). On the other hand, linseed supplementation reduced concentrations of long chain n-3 (EPA and DPA) in Experiment 2, conforming to a recent meta-analysis citing a range of studies in which linseed and other oil supplements decreased concentrations of long chain (>18 C) unsaturated FA (Glasser et al, 2008).…”

“…The method used for the FA analysis of milk samples in Experiment 1 was previously described by Butler et al (2011). An improved analytical method was used in Experiment 2, which was based on the methylation and esterification protocols for milk FA described by Chilliard, Martin, Rouel, and Doreau (2009).…”

“…F, 1973). Fifty mg of the extracted lipid was transferred in a glass tube and the same methylation and esterification procedure was followed as described in Butler et al (2011).…”

“…However, when cows are housed, the milk concentrations of desirable MUFA and PUFA are known to decrease, due to lack of fresh forage in the diet. Seasonal changes in dairy diets on many farms have been shown to result in variable milk fat composition throughout the year with differences being more marked in organic systems where high intakes of grazed forage in summer are replaced with conserved forage based diets in winter (Butler, Stergiadis, Seal, Eyre, & Leifert, 2011;Stergiadis et al, 2012). Therefore, there is a need to develop strategies to improve winter milk quality in both conventional and organic production systems.…”

Quality of cows' milk from organic and conventional farming

“…There are a number of comparative studies on the composition and properties of organic and conventional cows' milks. According to some authors, milk from organically certified systems contains more polyunsaturated fatty acids including n-3 polyunsaturated fatty acids and CLA (Ellis et al 2006;Bloksma et al 2008;Popović-Vranjes et al 2010;Butler et al 2011b), vitamins, and calcium (Bergamo et al 2003;Butler et al 2008). The more favourable fatty acids profile of organic milk in these studies has been mainly associated with organic diets richer in fresh grass and clover which conventional diets are based on silage and concentrates.…”