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Beef production on continuously stocked grass and grass/clover swards

L. Carlier and A. De Vliegher

Government Plant Breeding Institute, Burg. Van Gansberghelaan 109, 9820 Merelbeke Belgium

Material and methods
Results and discussion


In the seventies the grazing system in Belgium changed on more than 60 % of the farms from rotational grazing to continuous stocking management.

For cows the output of milk production per ha on both systems was not significantly different but the cows behaved more quietly and calmly while continuously stocked. For bulls the rotational grazing system gave better results in terms of kg liveweight gain/ha (Carlier and Andries 1981).

These grass swards received on average more than 300 kg/ha/yr, white clover mostly being absent.

Knowing that clover-rich grassland is better consumed than pure grass, the question was what would be the result in terms of beef production on a continuously stocked grass/clover sward with half the nitrogen supply of a continuously stocked pure grass sward.

Material and methods

During the period 1982-1986 bulls were set stocked on two types of grassland. The first area was established in September 1981 with perennial ryegrass (var. Vigor 25 kg/ha), the other with an additional 3 kg/ha white clover (vars. Wilkla and Blanca).

The grass sward was fertilised with 80 kg N/ha each year at the end of February and thereafter on with 55 kg N/ha every 3 weeks from the first grazing day on. The grass clover sward received each time half the dose of nitrogen. P and K were given in the same quantity on both blocs in agreement with the soil analyses. The bulls (white blue race of Middle and High Belgium) received the same diet of maize silage ad lib + 0, 5 kg of soyabean meal during the previous winter period and weighed about 400 kg at the beginning of the grazing season. All bulls were treated with a paratect bolus before they went outside. The stocking rate/ha was the same on both grass blocs. Adaptation of the stocking rate to the grass quantity on offer was based on the put and take method.

Thus, the grass height was measured 3 times a week and from the time grass height went under 7 cm some bulls were taken off until grass height again reached 12 cm. The bulls did not receive any fodder supplement.

Grass production on both systems was measured each month by taking the difference between the grass grown under cages next to strips mown 12 days before; the grass was mown to a stubble length of 4 cm each time. Samples were taken for analyzing the chemical composition of both swards every 2 weeks and the clover content was measured at the beginning, the middle and end of each grazing season.

Results and discussion

The animal production results from the continuously stocked grass and grass/clover sward are summarized in table 1.

Table 1: Daily growth and total animal production from bulls on continuously stocked grass and grass clover swards (average figures from 1982 to 1986)

Grass sward

Grass + clover sward

kg N/ha/yr



grazing period: days



weight of bulls at start (kg)



bulls/ha at start



bulls/ha over the season



liveweights gain/day/bull (kg)



beef production/ha/season (kg)



surplus of grass mown (1): kg dry matter/ha



(1) During the first three years of the trial grass surplus in May was mown

In table 2 some details about the two types of swards are given.

Table 2: Average grass production (kg dr matter/ha/day), grass height (cm), chemical composition (as % of the dry matter) and % of white clover (1982-1986).


Grass + clover

kg dm produced/ha/day



grass height: cm



Chemical composition:

% d.m



% ash



% crude protein



% N.D.F.



digestibility org. mat. in vitro



in '82



clover content (%)

in '84



in '86



From these average results (Table 1) can be concluded that bulls on a well managed grass/clover sward, with half the quantity of nitrogen per ha, can give the same daily growth and total output of beef per ha. This means that this grazing system gives better financial results than the continuously stocked pure grass sward. Laidlaw and Frame (1988) suggested that systems based on white clover are capable of producing 80 % or more animal product of that expected from intensive systems using high rates of N fertilizer.

The average daily grass production/ha, over the whole grazing period from the beginning of May till the end of September, was 12 kg higher on the grassland with high N-level and the sward height was measured 0, 9 cm higher. During the first 3 years this grass surplus, especially situated in May, was mown for fodder conservation. In the first and second year after sowing the clover content in the sward was higher than 30 % but later on the clover content decreased to 20 %. So the presence of this clover percentage couldn't fully compensate the impact of the lower nitrogen level/ha on the dry matter production of the sward.

The good animal performance from continuously stocked grass/white clover swards which ostensibly have insufficient clover content to make such an impact can be explained by the fact that the clover in the animal diet and the actual contribution of clover to sward productivity is underestimated by the clover content (Laidlaw and Frame, 1988). However in this experiment (Table 2) the grass/clover sward produced less herbage dry matter than the heavily fertilized pure grass sward and this in agreement with the statements of Robson et al. 1989.

In continuously grazed swards, clover tends to thin out over a period of 3 or 4 years (Davies, 1992), a phenomenon also stated in this trial. The use of grass/clover pastures appeared potentially profitable where fertilizer N usage is below 200 kg/ha annually (Doyle et al., 1984).

Animal performance (beef, lamb, milk) is greater with clover than with grass (Thomson, 1984). This has not always been the case in grazing trials (Frame, 1990). The differences in chemical composition in this experiment are mainly due to the difference in grass height. The grass/clover sward measured on average about 1 cm lower, so the leaf/stem ratio was lower and therefore also the protein content and the digestibility. The dry matter and neutral detergent fibre content, on the other hand, were higher.

Nevertheless daily gain per animal on the grass clover sward was as good as on the pure grass sward. Undoubtedly, a more disciplined standard of management is required than for nitrogen fertilised grass swards since it is less easy to "nurse" the clover back, should it be adversely affected by mismanagement than it is to boost the productivity of a grass sward by fertilizer N (Frame, 1990).


From a 5-year trial it could be concluded that the animal output in daily gain per animal and beef production per hectare, was the same on a continuously stocked grass clover sward, dressed with half the nitrogen quantity of a continuously stocked pure grass sward. Economically and ecologically this system gives good perspectives.


CARLIER, L.A. and ANDRIES, A.P. (1981) Exploitation des prairies. 3. Analyse comparative du pâturage continu et du pâturage tournant pour la vache laitière et le bétail a l'engrais. Revue de l'Agriculture 34, 493-509

DAVIES, A. (1992) White clover. Biologist 39, 129-133

DOYLE, C.J.; MORRISON, J.; BROCKMAN, J.S.; CAMM, B.M. and REEKS, J. (1984) Practical potential of legumes: an economic assessment. Occasional Symposium of the British Grassland Society. N° 16, 152-165

FRAME, J. (1990) Exploiting grass/white clover swards. II Utilization and animal performance. West of Scotland College Publication, Auchincruive, Ayr, 26 pp.

LAIDLAW, A.S. and FRAME, J. (1988) Maximising the use of the legume in grassland systems. Proceedings of the 12th General Meeting of the European Grassland Federation. Dublin. Ireland, pp. 34-36.

ROBSON, M.J.; PARSONS, A.J. and WILLIAMS, T.E. (1989) Herbage production: grasses and legumes. In: Grass. Its production and utilisation. 2nd edition (W. Holmes, ed.), pp. 7-88. Oxford: Blackwell Scientific Publications.

THOMSON, D.J. (1984) The nutritive value of white clover. Occasional Symposium of the British Grassland Society. N° 16, pp. 78-92

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