Elgersma, A.

Wever, A.C.

Witkowska, I.M.

English

Name not available

Factors affecting the fatty acid pattern of Lolium perenne

Wageningen Yield 

 Grassland Science in Europe, Vol. 11 454
Factors affecting the fatty acid patterns of Lolium perenne 
 
Witkowska I. M., Wever A. C. and Elgersma A. 
 
Crop and Weed Ecology Group (CWE), Department of Plant Sciences, Wageningen University, 
Haarweg 333, 6709 RZ Wageningen, The Netherlands. 
 
Abstract 
 
Fresh forages provide the most natural and environmentally sustainable source of fatty acids (FA) for 
ruminants. Several factors influence the concentration and proportion of FA in herbage. This study 
evaluated the influence of N application levels (0, 45 and 100 kg N ha-1) and regrowth interval on the 
FA composition in Lolium perenne L. during three periods in 2004. In each experiment, the α-linolenic 
acid (C18:3) concentration decreased with an extended regrowth interval, whereas levels of C16:0 and 
C18:2 increased. Higher N application increased total FA and C18:3 concentrations. A positive 
correlation between herbage N and C18:3 concentrations was established throughout the entire period. 
Moreover, total FA, and C18:3 concentration and proportion gradually increased with N fertilization 
level, from May to October. Grassland management can affect levels of FA in herbage, which is 
important for the quality of ruminant products.  
 
Keywords: Lolium perenne, herbage, nitrogen, fertilization, regrowth interval, fatty acids. 
 
Introduction 
 
The lipid fraction in leaves of forage species ranges from 30 – 100 g kg-1 dry matter (DM) High fatty 
acid (FA) concentrations occur during primary growth, leafy regrowth, and late in the season (Bauchart 
et al., 1984). Besides, Hawke (1973) reported a positive correlation between the amounts of FA and the 
chlorophyll concentration in a leaf tissue. The chlorophyll concentration is affected by the solar 
radiation and by the nutrition of the plant. The primary nutrient, nitrogen, is a necessary part of all 
proteins, enzymes, and metabolic processes involved in the synthesis and transfer of energy. 
Consequently, with a sufficient supply of N, levels of all plant proteins as well as the density or mass of 
chloroplast and perhaps associated lipids raise, giving a plant the “lush” appearance. Still, the nature and 
interactions between factors influencing the FA levels in herbage remain unclear. As forage is a cheap 
and environmentally sustainable source of FA, these relationships are important to enhance levels of 
beneficial FA in ruminant products. Thereby, this study evaluated the influence of N application levels 
and regrowth interval on FA composition of Lolium perenne during three periods in 2004.  
 
Material and methods 
 
The experiment was conducted at an experimental field of Wageningen University, the Netherlands. 
The experimental set-up was a randomized block design with three replicates (Elgersma et al., 2005). 
Three N treatments (0, 45 and 100 kg N ha-1) were applied before three subsequent periods (May – June, 
Aug. – Sept., and Oct.) in 2004. During each period, three harvest dates were chosen to simulate various 
cutting regimes (early, normal, and late). Fresh herbage was sampled immediately with dry ice and 
stored in a freezer (-18˚C), before analysis of FA. Other random samples of the herbage were taken to 
asses the DM content and morphological characteristics. Samples used for DM determination were 
analyzed for total nitrogen and water-soluble carbohydrates. Multiple regression analyses were carried 
out, according to a model taking account of the effects of period, N fertilization and regrowth interval, 
as well as period x N fertilization, period x regrowth interval, N fertilization x regrowth interval and 
period x N fertilization x regrowth interval. Moreover, regression analyses were conducted between 
chemical variables and FA concentrations to establish overall relationships based on measured plant 
characteristics. 
 
 Sustainable Grassland Productivity 455
Results and discussion  
 
The most distinct differences in all analyzed herbage chemical characteristics were reported between 
material collected in May – June (reproductive development stage), Aug. – Sept., and Oct. (vegetative 
development stage). The highest WSC and lowest N and FA concentrations occurred in the first period, 
while during the following months the WSC concentrations decreased, and N and FA concentrations 
increased (P < 0.05; Figure 1 and 2) (Hawke, 1973).  
 
0
50
100
150
200
250
300
350
400
0 10 20 30 40 50 60
N (g kg
-1
 DM)
W
S
C
 (
g
 k
g
-1
 D
M
)
100N May-June
100N Aug.-Sept.
100N Oct.
45N May-June
45N Aug.-Sept.
45N Oct.
0N May-June
0N Aug.-Sept.
0N Oct.
 
 
Figure 1. The relation between WSC and N (g kg-1 DM) of Lolium perenne during three periods in 
2004; N = 367.44 – 7.49 * WSC; R2 = 0.79. 
 
The differences in the herbage nutritive value observed during the entire experiment might be explained 
in three ways. Firstly, the nutritive value of morphological forage fractions and their proportions derives 
the nutritive value of the forage. Since, in May – June the leaf blade proportion was smallest, the 
concentrations of N and FA were lower, and WSC higher than in the following months. Secondly, an 
accumulation of DM with the regrowth interval negatively influences the nutritive value of the herbage. 
High herbage yields coupled with a considerable increase in the yield with an extended regrowth 
interval (45N-20d: 1.9 ± 0.2 t ha-1 vs. 45N-32d: 4.2 ± 0.8 t ha-1) were only reported in May – June, when 
weather conditions were favourable for herbage growth. In subsequent periods, the yields were 
approximately 50% lower, as the growth was limited by either high temperature (Aug. – Sept.) or low 
solar radiation (Oct.). Thirdly, the photosynthetic rate decreases with the herbage age, leading to 
reduced synthesis of metabolic components, such as proteins, chlorophyll, and FA (Hawke, 1973). 
Therefore, with the extended regrowth interval, the concentrations of N, total major FA and C18:3 
decreased (P < 0.01), while the concentrations of WSC, C16:0 and C18:2 increased (P < 0.001). 
Besides, higher N fertilization levels increased concentrations of FA (P < 0.01). The N fertilization 
promotes photosynthesis, by increasing the leaf area (light harvesting part of the plant) and the synthesis 
of metabolic components, such as chloroplast and proteins. Pigment-protein complexes, composed of 
proteins, chlorophylls, and FA are constituents of chloroplast thylakoid membranes (Evans, 1996), and 
are directly responsible for the harvesting of the solar radiation. We can speculate, based on the 
previously reported positive relationship between chlorophyll and FA (Hawke, 1973), that this 
relationship should be valid for all main constituents of these complexes. This might be an explanation 
for the positive correlation between N and C18:3 concentrations established throughout the entire 
experiment (Figure 2). 
 
 Grassland Science in Europe, Vol. 11 456
0
5
10
15
20
25
30
35
0 10 20 30 40 50 60
N (g kg
-1
 DM)
C
1
8
:3
 (
g
 k
g
-1
 D
M
)
100N May-June
100N Aug.-Sept.
100N Oct.
45N May-June
45N Aug.-Sept.
45N Oct.
0N May-June
0N Aug.-Sept.
0N Oct.
 
 
Figure 2. The relation between N and C18:3 concentration (g kg-1 DM) of Lolium perenne during three 
periods in 2004; C18:3 concentration = 0.49 + 0.59 * N; R2 = 0.87. 
 
Conclusions 
  
Grassland management can enhance levels of important FA in herbage. Frequent cutting of the sward 
results not only in a higher nutritive value of forage, but also in higher levels of FA. It seems to be 
especially important in spring, when the rate of herbage growth is highest. N fertilization also seems to 
be an attractive way for enhancing levels of FA in herbage. Nonetheless, large seasonal variations in the 
concentrations of WSC, N, and FA in the herbage exist. Further research is required to explore these 
relationships on more fundamental plant level.  
 
Referentes 
 
Bauchart D., Vérité R., Remond B. (1984) Long-chain fatty acids digestion in lactating cows fed fresh 
grass from spring to autumn. Canadian Journal of Animal Nutrition (Suppl.), 330-331. 
Elgersma A., Maudet P., Witkowska I., Wever C. (2005) Effects of N fertilization and regrowth period 
on the fatty acid composition of perennial ryegrass (Lolium perenne L.), Annals of Applied Biology 
(in press).  
Evans J.R. (1996) Developmental constrains on photosynthesis: Effects of light and nutrition. In: Baker 
N.R. (editor) Advances in Photosynthesis and the environment 5, Kluwer Academic Publishers, 
Heidelberg,  
Germany, pp. 281-304.   
Hawke J.C. (1973) Lipids. In: Butler U.W. and Bailey R.W. (eds) Chemistry and biochemistry of 
herbage, Academic Press, London, UK, pp. 213-263. 


Factors affecting the fatty acid pattern of Lolium perenne

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