Seasonal variation in fatty acid contents of cow milk from indoor and pasture-based feeding
Wyss U.1, Collomb M.1, Frey H.J.2 and Hofstetter P.3
1Agroscope Liebefeld-Posieux Research Station ALP, Posieux, Switzerland
2Hohenrain Agricultural Education and Extension Centre, Hohenrain, Switzerland
3Schüpfheim Agricultural Education and Extension Centre, Schüpfheim, Switzerland Corresponding author: ueli.wyss@alp.admin.ch
Abstract
The objective of this study was to compare the fatty acid contents in two systems of milk production. One system was pasture-based (P) with the calving season between February and April and with a restricted concentrate supplementation of 290 kg cow-1 y-1. The second system used indoor feeding (I) with a mixed ration of grass and maize silage as well as a supplementation of concentrates (1135 kg cow-1 y-1). The calving season was mainly between June and September. In 2008 and 2009, every month tank milk samples were taken and the fatty acid composition in the milk fat was analysed. The milk production was 5800 kg cow-1 y-1 in system P and 8400 kg cow-1 y-1 in system I. The milk of system P had less saturated and more unsaturated fatty acids in comparison to I. The conjugated linoleic acid in fat increased continuously from spring to autumn to 2.5 g (100 g)-1 in system P while it amounted 0.5 g (100 g)-1 during the whole year in system I. Differences were also found in the omega-3 acid content. In system P the contents were always higher than in I.
Keywords: pasture-based system, indoor feeding system, fatty acid content, omega-3 Introduction
Bovine milk contains a large number of fatty acids (FA), some of which may be of potential benefit to human health, including polyunsaturated FA as omega-3 and conjugated linoleic acids (CLA). Many factors affect the FA composition of bovine milk. Compared with total mixed rations, pasture-based diets resulted in higher concentrations of unsaturated long-chain FA and CLA in milk (Kelly et al., 1998; White et al., 2001). The objectives of this study were to determine the effects of two different feeding systems on the FA composition in the milk and to investigate the development of the different FA during the year.
Materials and methods
Two systems of milk production were compared on 13 ha each in Hohenrain (altitude 620 m a.s.l.). One system was pasture-based (P) with the calving season between February and April; 27 cows in 2008 and 28 cows in 2009 belonged to this system. The concentrate feed was restricted to 290 kg cow-1 y-1. The pasture period started on 17 March in 2008 and 18 March in 2009, at first only during the day and then day and night. The pasture period lasted until 11 November in 2008 and 18 November in 2009. The second system used indoor feeding (I) with a mixed ration of grass and maize silage as well as a supplementation of concentrates of 1135 kg cow-1 y-1. The calving season was mainly between June and September. This herd consisted of 25 cows in 2008 and 24 cows in 2009.
Every month, tank milk samples were taken and the FA in the milk fat were analysed according to Collomb and Bühler (2000).
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Results and discussion
In system P the average milk production was 5800 kg cow-1 y-1. The indoor feeding system yielded a higher milk production of 8400 kg cow-1 y-1. Due to the seasonal calving period the average milk production per cow decreased in system P continuously. In system I, with the calving period over the whole year but with an accumulation between June and September, the average milk production was more stable, with a little increase at the end of summer (Figure 1). In system P the average milk fat content decreased first and then increased towards the end of lactation. In system I the milk fat content of the tank milk samples was higher than in system P with less seasonal variation (Figure 2).
Figure 1. Evolution of the average milk production
Figure 2. Evolution of the milk fat content
The milk of system P had less saturated and more mono- and poly-unsaturated FA in comparison to I, especially from April to October when the cows were on the pasture day and night (Figures 3 to 5).
Figure 3. Evolution of the saturated fatty acids (SFA)
Figure 4. Evolution of the mono-unsaturated fatty acids (MUFA)
In system P the conjugated linoleic acid (CLA) increased continuously until September to a maximum of 2.5 g (100 g)-1 fat with both years being very similar (Figure 6). In system I, the CLA content in fat amounted 0.5 g (100 g)-1 during the whole year. The CLA contents from system P as well as the development during the grazing season were similar to the results obtained by Collomb et al. (2008) from milk from mountain regions in Switzerland. The omega-3 FA also increased during the grazing season in system P in both years (Figure 7). In system I the values were lower than in system P and varied little.
The omega-6 FA was not influenced by the grazing season (Figure 8). The omega-6 contents of the system I were higher in comparison to system P.
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Figure 5. Evolution of the conjugated acids (PUFA)
Figure 6. Evolution of the poly-unsaturated fatty linoleic acids (CLA)
Figure 7. Evolution of the Omega-3 fatty acids
Figure 8. Evolution of the Omega-6 fatty acids
Conclusions
x Milk of grazing cows had less saturated and more mono- and poly-unsaturated FA than milk from cows fed conserved forage and a higher supplementation of concentrates.
x Milk from grazing cows had higher amounts of CLA and omega-3 FA in comparison to milk from cows fed conserved forage and a higher supplementation of concentrates.
x CLA and omega-3 FAs increased during the grazing season from March to September.
References
Collomb M. and Bühler T. (2000) Analyse de la composition en acides gras de la graisse de lait. I. Optimisation et validation d’une méthode générale à haute résolution. Mitteilungen aus Lebensmitteluntersuchung und Hygiene 91, 306-332.
Collomb M., Bisig W., Bütikofer U., Sieber R., Bregy M. and Etter L. (2008) Seasonal variation in the fatty acid composition of milk supplied to dairies in the mountain regions of Switzerland. Dairy Science Technology 88, 631-647.
Kelly M.L., Kolver E.S., Bauman D.E., van Amburgh M.E. and Muller L.D. (1998) Effect of intake of pasture on concentrations of conjugated linoleic acid im milk of lactating cows. Journal of Dairy Science 81, 1630-1636.
White S.L., Bertrand J.A., Wade M.R., Washburn S.P., Green J.T. and Jenkins T.C. (2001) Comparison of fatty acid content of milk from Jersey and Holstein cows consuming pasture or total mixed ration. Journal of Dairy Science 84, 2295-2301.
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