Abstract preview
EGF 2008
Species rich limestone grasslands of the Burren, Ireland: feed value and
sustainable grazing systems
Moran J. 1, 2, Parr S. 2, Dunford B. 2, O’ Conchúir R. 2
1
Teagasc, Environment Unit, Athenry, Co. Galway, Ireland
2
BurrenLIFE Project, Carran, Co. Clare, Ireland
Corresponding author: [email protected]
Published in: Grassland Sciences in Europe (2008), vol 13, pp150-152
Abstract
Winter grazing of the limestone grasslands, pavements and heaths of the Burren is a key
factor in maintaining their biodiversity. Over the last 30 years farmers have moved away from
store cattle to the grazing of suckler cows. The higher nutritional requirements of in-calf cows
resulted in many farmers introducing silage onto winter grazed areas (winterage) or housing
animals. This led to reduced grazing on winterages and to farm polarization (intensification
and reseeding of improved agricultural grassland, while abandoning semi-natural grassland on
the same farm). An EU LIFE Nature funded project ‘BurrenLIFE’, is developing a new model
for sustainable agriculture in the Burren. Central to this is the introduction of grazing regimes
which seek to optimize utilization of the valuable forage resource on winterages, while
maintaining biodiversity. To profile the forage quality of winterage, a range of vegetation
types have been sampled and analysed to determine their ash, nitrogen, crude protein, oven
dry matter, acid detergent fibre, neutral detergent fibre and trace mineral contents. Results
show variations in forage quality during the winter grazing season and between vegetation
types. Forage quality results suggest that Burren winterages do not meet the nutritional
requirements of suckler cows from December to March.
Keywords: burren, grazing, limestone grasslands, forage quality
Introduction
The Burren is a unique farmed landscape of limestone pavement, grasslands, heaths and
wetlands located in the west of Ireland. Approximately 30,000 ha are designated as special
areas of conservation (SAC), forming part of Europe’s Natura 2000 ecological network of
protected sites. Traditional farming practices, in particular winter grazing with minimal
external inputs, are important in maintaining the good ecological status of the Burren
(Dunford, 2002). Over the past 30 years agriculture in the Burren has undergone substantial
change, including the switch from store cattle to suckler beef production and concentration of
agricultural activities on agriculturally improved grasslands. The higher nutritional
requirements of in-calf cows resulted in many farmers introducing silage onto winter grazed
areas (winterage) or housing animals over the winter. Silage feeding leads to animals foraging
far less, leading to undergrazing and point source pollution around feeding sites, while the
housing of animals results in the abandonment of winter-grazed grasslands and the loss of
important management traditions. BurrenLIFE, an EU LIFE-Nature funded project has been
set up to develop a new model of sustainable agricultural management for the priority habitats
of the Burren. Central to this is the introduction of grazing regimes making use of the valuable
forage resource on farms while maintaining biodiversity. The ongoing analysis of the forage
quality on Burren winterages is being used to ascertain if Burren winterages meet the
nutritional requirements of suckler cows, which are the most prevalent livestock type on the
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Abstract preview
EGF 2008
winterages. This aims to encourage sustainable grazing levels on conservation grasslands
while meeting the nutritional needs of the grazing animal.
Materials and methods
Twenty BurrenLIFE monitor farms were selected across the Burren using criteria such as
SAC area, types of habitat, grazing levels and farming system. BurrenLIFE monitor farms
cover 3097 ha of which 2486 ha are designated as SAC. To profile the forage quality of
Burren winterage grasslands, they were divided into 5 broad types based on previous research,
which are: (a) Molinia caerulea dominant, (b) Dryas octapetala dominant (c) Sesleria
caerulea and Festuca sp. dominant, (d) Calluna vulgaris approximately 25% cover and (e)
Anthoxanthum odoratum, Cynosurus cristatus and Dactylis glomerata dominant. 50 sample
areas representing these vegetation types were selected across the monitor farms. Samples
were collected every two months during the late summer and winter grazing periods from
August to April, from December 2005 until April 2007. Sample locations were located using
a GPS and approximately 500 g of forage were cut using clippers. Samples were analysed for
ash, N (Kjeldahl nitrogen), crude protein (CP) (N x 6.25), oven dry matter, acid detergent
fibre (ADF) and neutral detergent fibre (NDF) (Van Soest analysis) at the Agri-Food and
Biosciences Institute, Northern Ireland. Trace mineral analysis was carried out on samples
collected in December 2006 using inductively coupled plasma-mass spectroscopy (ICP-MS)
to ascertain elemental concentrations (Cu, Mn, Mo, Se, Zn, Ca, K, Mg, P and I) at the
Macaulay Institute, Scotland.
The vascular plant species in 2 x 2 m quadrats at each sampling site were recorded and their
cover estimated using the Domin scale. These data were used to accurately assign each
sampling location to a vegetation type using cluster analysis (PC-ORD vers. 5: relative
Euclidean distance measure and wards linkage method) and indicator species analysis.
Results and discussion
Cluster analysis divided the 50 samples into 6 vegetation types (Table 1). These approximate
the M25b (Molinia caerulea-Potentilla erecta mire, Anthoxanthum odoratum subcommunity), CG9 (Sesleria caerulea -Galium sterneri grassland), CG13 (Dryas octapetalaCarex flacca heath), intermediate between CG9/CG1 (Sesleria caerulea-Festuca grassland),
MG5b (Cynosurus cristatus-Centaurea nigra, Galium verum sub-community) and an
enriched MG5 (Cynosurus cristatus-Centaurea nigra with weedy element) vegetation
communities of the national vegetation classification of Britain (Rodwell et al., 1992).
Table 1: Mean ± s.e.m. of forage quality variables for Burren winterage vegetation types.
Veg Type (sites)
Molinia caerulea mire (5)
Sesleria caerulea grassland (7)
Dryas octapetala heath (12)
Sesleria caerulea-Festuca
grassland (10)
Cynosurus cristatus-Centaurea
nigra grassland (12)
enriched Cynosurus cristatusCentaurea nigra grassland (4)
Total
N
37
56
93
74
DM g kg
412.1±31.8
384.1±15.9
383.3±12.9
346.2±13.7
Ash g kg-1
DM
29.6±1.8
35.1±1.5
38.5±1.0
42.7±1.3
96
303.3±12.5
58.1±2.2
95.6±2.4
390.0±5.4
698.9±7.1
32
272.6±23.0
68.1±5.4
122.8±6.7
357.0±9.9
675.4±14.8
388
349.7±6.9
45.3±1.0
82.7±1.3
408.0±2.8
711.3±3.8
-1
CP g kg-1
DM
63.1±3.8
66.5±1.7
72.1±1.3
84.3±1.8
ADF g kg -1
DM
432.2±8.5
423.9±6.2
427.4±4.9
405.2±6.4
NDF g kg-1
DM
782.8±10.4
725.0±7.8
711.8±6.9
696.6±9.9
Univariate analysis of variance of the forage quality shows that there are significant
differences (P<0.01) in the CP, ADF and NDF of the different vegetation types on Burren
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EGF 2008
winterages. The vegetation communities of highest conservation importance and listed as
priority habitats for conservation under the EU Habitats directive (i.e. CG 9 and CG13) are
dependent on winter grazing to maintain their conservation value (Dunford, 2002). Results in
this study indicate that these grasslands have low average CP and high ADF values on Burren
winterages (Table 1). Crude protein values below 70 g kg-1 DM have been shown to limit
fibre digestion in the rumen (Allison, 1985). As expected there is considerable seasonal
variation in forage quality (Figure 1). Forage quality decreases as growth slows from August
to December as indicated by increases in ADF and decreases in CP values. Forage quality is
at its lowest from December to February and improves from February to April. Trace mineral
analysis showed that Burren winterage vegetation is deficient in Cu (<5 mg kg-1 DM),
Se (<0.10 mg kg-1 DM), Mg (<2 g kg-1 DM) and P (<2 g kg-1 DM) (Source: Rogers et al.,
2000).
(B) Mean Crude Protein
(A) Mean Acid Detergent Fibre
Veg. Type
500.0
175.0
M25b
CG9
CG13
CG9/CG1
MG5b
MG5
150.0
CP g kg-1 DM
ADF g kg-1 DM
450.0
400.0
125.0
100.0
75.0
350.0
50.0
300.0
12DEC05
1220180817111917DEC- FEB- APR- AUG- OCT- DEC- FEB- APR05
06
06
06
06
06
07
07
20FEB06
18APR06
08AUG06
1711OCT- DEC06
06
19FEB07
17APR07
Date
Date
Figure 1: (A) Mean ADF and (B) Mean CP values for Burren winterage types from December
2006 to April 2007.
Conclusions
The results suggest that Burren winterages do not meet the nutritional requirements of suckler
cows, especially from December to March when cows are in late pregnancy. However, this
does not take into account selective grazing of more palatable vegetation, which may result in
consumption of forage of higher quality than suggested by this study. Supplementation with
concentrate feed (replacing existing silage feeding) from December to March could meet the
maintenance requirements of cows and increase the supply of crude protein. This can increase
the breakdown and rate of passage of poor quality forages through the gut allowing the animal
to consume more (Romey and Gill, 2000). As a consequence improving the grazing levels on
winterage areas, allowing farmers to graze cows on winterage areas for longer, while meeting
their nutritional requirements without resorting to silage feeding or housing. Concentrate
supplementation is currently being piloted by the BurrenLIFE project with initial positive
feedback from the farmers involved.
References
Allison C.D. (1985) Factors affecting forage intake by range ruminants: a review. Journal of Range
Management, 38, 305-311.
Dunford B. (2002) Farming and the Burren, Teagasc Publications, Oak Park, Carlow, Ireland, 108 pp.
Rodwell J.S., Piggott C.D., Ratcliffe D.A., Mallock A.J.C., Birks H.J.B., Proctor M.C.F., Shimwell D.W.,
Huntley J.P., Radford E., Wigginton M.J. and Wilkins P. (1992) British Plant Communities. Volume 3.
Grassland and montane communities. Cambridge University Press. Cambridge, UK, 540 pp.
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EGF 2008
Rogers P., Gately T. and Keating T. (2001) Teagasc farm nutrient profile: reference information for
professionals. Teagasc Publications, Oak Park, Carlow, Ireland, 20pp.
Romey D.L. and Gill M. (2000) Intake of Forages. In: Givens D.I., Owen E., Axford R.F.E. and Omed H.M.
Forage Evaluation in Ruminant Nutrition, CAB International, Wallingford, UK, pp. 43-62.
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