400 Grassland Science in Europe, Vol. 17 Fatty acid composition of three different grassland species
Wyss U.
Agroscope Liebefeld-Posieux Research Station ALP-Haras, 1725 Posieux, Switzerland Corresponding author: ueli.wyss@alp.admin.ch
Abstract
The botanical composition and the growth stage of forage influence the milk fatty acid profile. In an experiment, the fatty acids composition of the three grassland species Dactylis glomerata, Medicago sativa and Taraxacum officinale was investigated. Forage of the first cut was harvested at four different dates, and different plant parts – stems, leaves and flow- ers – were collected separately and analysed. The samples were freeze-dried and the fatty acids determined by gas chromatography. In addition, the nutrient contents were analysed.
The α-linolenic acid (C 18:3 c9c12c15) was the most dominant fatty acid for D. glomerata and M. sativa, though for T. officinale this was the case only in the early growth stage.
In the older forage, more linoleic acid (C 18:2 c9c12) was produced.
For all three species, total fatty acids decreased from the first to the fourth cutting date.
The leaves and flowers contained more fatty acids than the stems. The biggest differences between stems and leaves were found for D. glomerata. The highest contents of linoleic acid (C 18:2 c9c12) were found in the flowers of T. officinale.
Keywords: grassland species, growth stage, fatty acids, linolenic acid, linoleic acid Introduction
The botanical composition and growth stage of forage influence the milk fatty acid profile (Ferlay et al., 2006). There are several fatty acids in plants, the most important of which are α-linolenic acid, linoleic acid and palmitic acid (Bauchart et al., 1984). Wyss and Col- lomb (2010) and Warner et al. (2010) found differences in the fatty acid concentration of different grasses, legumes and herbs. The different fatty acids decreased with the age of the forage, especially in the forage of the first growth.
The objective of this study was to investigate the fatty acid concentration in different plant parts of three different grassland species at different growth stages.
Materials and methods
The fatty acid composition of the grass Dactylis glomerata, the legume Medicago sativa and the herb Taraxacum officinale was investigated. All species were grown at Posieux (altitude 650 m a.s.l.). Forage of the first cut was harvested at four different dates. In addi- tion, the different plant parts – stems, leaves and flowers – were collected separately and analysed, although the three plant species had not always developed stems and flowers at all the harvested dates. The samples were freeze-dried and the fatty acids were determined by gas chromatography (Alves et al., 2008). In addition, for the whole plants, samples were dried at 60°C, milled, and the ash, crude protein and fibre contents were analysed. Results for fatty acid concentrations were analysed by analysis of variance.
Results and discussion
The nutrient contents of the three different grassland species are shown in Table 1. With increasing age of the plants the crude protein (CP) decreased and the fibre contents, acid detergent fibre (ADF) and neutral detergent fibre (NDF), increased.
Grassland – a European Resource? 401 Table 1. Nutrient contents in three species and four cutting dates of the first growth
Species Cutting date DM Ash CP ADF NDF
g kg–1 g kg–1 DM g kg–1 DM g kg–1 DM g kg–1 DM
Dactylis glomerata 03.05. 226 96 206 252 427
17.05. 213 74 212 253 427
31.05. 252 51 137 277 498
14.06. 260 48 95 375 611
Medicago sativa 03.05. 185 89 239 200 277
17.05. 226 78 202 269 312
31.05. 300 68 155 335 414
14.06. 262 82 151 357 431
Taraxacum officinale 20.04. 154 106 235 179 191
03.05. 110 90 162 202 206
17.05. 116 83 144 204 214
31.05. 127 118 111 251 258
The total fatty acids (TFA), α-linolenic acid, linoleic acid and palmitic acid were sig- nificantly different between the three species and cutting dates (Table 2). The highest fatty acid concentrations were found for all three plants in the young forage. The herb T.
officinale always had higher concentrations of linoleic (C18:2 c9,c12) and palmitic acid (C16:0) in comparison with D. glomerata and M. sativa. Bauchart et al. (1984) also found the highest fatty acid concentrations in early May. The results were similar to the results of an earlier study (Wyss and Collomb, 2010).
Table 2. Fatty acid concentrations in three species and four cutting dates of the first growth (g kg–1 DM)
Species Cutting date C16:0 C18:2 c9,c12 C18:3 c9c12c15 TFA
Dactylis glomerata 03.05. 4.3 4.1 20.1 34.6
17.05. 4.2 4.4 20.4 34.5
31.05. 3.6 4.5 15.4 28.1
14.06. 3.0 3.3 10.7 21.1
Medicago sativa 03.05. 5.1 6.8 17.3 34.8
17.05. 5.0 6.7 15.3 32.2
31.05. 4.1 5.1 12.0 25.6
14.06. 3.8 4.6 10.8 23.4
Taraxacum officinale 03.05. 6.8 10.0 16.4 39.2
17.05. 5.6 12.9 16.0 40.0
31.05. 4.4 10.4 9.2 28.9
Standard deviation 0.34 0.73 1.14 1.48
Species (S) *** *** *** ***
Cutting date (D) *** *** *** ***
Interaction S × D *** *** *** ***
*** P < 0.001.
The separation of the different plant parts showed that the concentration of the fatty acids strongly varied within the plants (Table 3). For D. glomerata big differences were found between the stems, as compared with the leaves and flowers. For M. sativa and T. of- ficinale differences were also found between the different plant parts, but the differences were smaller than in D. glomerata. A high accumulation of linoleic acid was found in the flowers of T. officinale.
402 Grassland Science in Europe, Vol. 17 Table 3. Fatty acid concentrations in the different plant parts of three species (g kg–1 DM)
Species Plant part Cutting date C16:0 C18:2 c9c12 C18:3
c9c12c15 TFA
Dactylis glomerata Stem 31.05. 2.1 1.5 2.3 7.1
14.06. 1.5 1.7 3.0 7.2
Leaves 31.05. 3.9 3.7 20.8 34.2
14.06. 3.6 3.6 15.0 28.2
Bloom 31.05. 3.8 7.0 8.9 25.1
14.06. 5.4 4.3 13.9 30.8
Medicago sativa Stem 03.05. 4.5 8.3 7.7 22.9
17.05. 4.1 8.1 7.3 22.3
31.05. 3.1 5.8 5.7 16.7
14.06. 2.5 4.0 4.1 12.2
Leaves 03.05. 6.1 6.3 24.7 45.0
17.05. 5.6 6.0 22.7 41.4
31.05. 5.5 5.5 23.5 41.3
14.06. 5.2 4.9 20.1 37.4
Bloom 14.06. 6.5 6.1 10.7 28.8
Taraxacum officinale Stem 03.05. 5.2 9.8 8.7 25.9
17.05. 4.2 7.4 7.3 20.7
31.05. 3.4 6.1 4.9 17.1
Leaves 03.05. 6.1 7.9 22.5 42.6
17.05. 5.6 8.3 22.7 42.4
31.05. 5.1 7.2 14.5 32.6
Bloom 03.05. 10.4 17.7 15.5 54.4
17.05. 7.9 26.6 8.2 54.0
31.05. 6.3 15.7 4.1 35.7
Standard deviation 0.88 2.18 2.95 4.97
Species (S) *** *** ns ***
Plant parts (P) *** *** *** ***
Interaction S × P ns *** ns **
** P > 0.01; *** P < 0.001; ns – non significant.
Conclusions
α-linolenic acid is the dominant fatty acid in the three investigated grassland species. For- age age is a important factor for the fatty acid concentration in the different plants. The concentrations of the different fatty acids vary between the different plant parts.
References
Alves S.P., Cabrita A.R.J., Fonseca A.J.M. and Bessa R.J.B. (2008) Improved method for fatty acid analysis in herbage based on direct transesterification followed by solid-phase extraction. Journal of Chromatog- raphy 1209, 212–219.
Bauchart D., Verite R. and Remond B. (1984) Long-chain fatty acid digestion in lactating cows fed fresh grass from spring to autumn. Canadian Journal of Animal Science 64 (Suppl.), 330–331.
Ferlay A., Martin B., Pradel P. Coulon J.P. and Chilliard Y. (2006) Influence of grass-based diets on milk fatty acid composition and milk lipolytic system in Tarentaise and Montbeliarde cow breeds. Journal of Dairy Science 89, 4026–4021.
Warner D., Jensen S.K., Cone J.W. and Elgersma A. (2010) Fatty acid composition of forage herb spe- cies. Grassland Science in Europe 15, 491–493.
Wyss U. and Collomb M. (2010) Fatty acid composition of different grassland species. Grassland Science in Europe 15, 631–633.
