agricultural production guidelines
m
Veld in KwaZulu-Natal
Co-ordinated Extension KwaZulu-Natal Veld 9.5 1999
IN GRAZING MANAGEMENT SYSTEMSDETERMINATION OF THE NUMBER OF CAMPS PER HERD
D M Gammon
Agric Foods, (Pvt) Ltd, P.O. Box 559, Bulawayo, Zimbabwe
J M B Smith
KwaZulu-Natal Department of Agriculture
Subdivision into
Homogeneous Areas
Animal Management
Provision of Rest Periods
Control of Defoliation
Number of
Camps for Rotational Grazing and Resting
Economic Considerations
INTRODUCTION
The optimum number of camps per herd in grazing systems has remained an unresolved controversy for many years. Early recommendations advocated approximately three camps per herd, while, more recently, different authorities have estimated the economic optimum to be about eight camps (Booysen, et al., 1974), or numbers in excess of this (Savory, 1978). Fencing and the provision of water are expensive investments, and careful consideration needs to be given to this question. The major objectives of subdivision of the veld, and their effects on the number of camps per herd, are discussed in this leaflet.
SUBDIVISION INTO HOMOGENEOUS AREAS
The first requirement for subdivision is the separation of areas of veld which differ in palatability and management requirements due to such factors as species composition, climate, soil type, topography and veld condition. Often the areas so formed are larger than the total area required by a herd, and do not affect the number of camps per herd. If these areas are smaller than the area required by a herd, these subdivisions provide the first justification for more than one camp per herd.
In practice, even if subdivisions are satisfactorily homogeneous, their size is often such that they are still unevenly utilized. Further subdivision may be justified purely to create smaller camps which will be more evenly, and more fully, utilized. Some increase in carrying capacity can be achieved through this action, which will add to the effects of rotational resting.
Camps need to be small enough to facilitate collection of animals for various operations. This is an important consideration in veld with a relatively low grazing capacity, particularly bushveld. For example, in veld with a grazing capacity of 5 ha/AU, a herd of 150 AU would require an area of 750 ha. Quite apart from veld management considerations, it would probably be desirable to divide this area into camps of 250 ha or less (i.e. three or more camps).
Often overlooked is the fact that the number of camps per herd depends, not only on the number of camps on a farm, but also on the number of herds run. The number of herds run should therefore be reduced to the minimum that is consistent with good animal management and performance (refer to Production Guideline 2.7 in this series).
Camps are necessary for rotational resting of the veld. The number of camps into which an area must be divided to meet this requirement depends on the desired frequency of resting. For example, if a rest is required once in four years, four camps will be necessary. If no other requirements were to be met, these four camps could carry three herds. This is the basis of the 3 herd/4 camp systems that have been used as elementary systems in various parts of the world.
Camps are necessary for rotational grazing of the veld, where the frequency and severity of defoliation is controlled. These aspects of defoliation can be controlled by manipulating the cycle length (time taken to complete one rotation through all the camps in a system), the period of stay (POS - the uninterrupted period that a herd occupies a camp), and the period of absence (POA - the period that a camp remains ungrazed between successive periods of stay). Refer to Production Guideline 9.4 in this series for more information on these concepts.
The relative importance of these concepts in a grazing system may vary in different circumstances. The cycle length sets the lower limit to the number of defoliations that can occur in a season (e.g. if the grazing season lasts 180 days, and the cycle length is 60 days, at least 3 defoliations can occur), and it affects the interval between defoliations. It should be long enough to set an acceptable limit to the number of defoliations that can occur in a season, but not so long that the herbage will become excessively mature and thus of low quality. The period of stay is controlled in order to prevent or minimise repeated defoliations within the period, and to ensure good animal performance. It should be short enough to achieve these objectives, but not so short as to result in too short a cycle length and period of absence. The period of absence sets the minimum interval that can occur between defoliations, and affects the quality of herbage available to animals. It should be long enough to permit sufficient recovery of grazed grass, but not so long as to produce poor-quality herbage.
The cycle length, period of stay, period of absence, and number of camps required per herd are interrelated, so that if values are set for any two of them the others can be calculated, as follows:
(CAMPS) = (CYCLE LENGTH)/(POS)
or
(CAMPS) = (POS)+(POA)/(POS)
(CYCLE LENGTH) = (POS) x (CAMPS)
or
(CYCLE LENGTH) = [(POA)/(CAMPS - 1)] x (CAMPS)
(POS) = (CYCLE LENGTH)/(CAMPS)
or
(POS) = (POA)/(CAMPS - 1)
(POA) = (POS) x (CAMPS - 1)
or
(POA) = [(CYCLE LENGTH)/(CAMPS)] x (CAMPS - 1)
Relations between the number of camps, the cycle length, the period of stay, and the period of absence are presented in Table 1. With any given cycle length, as the number of camps is increased, the period of stay decreases, and the period of absence increases. However, the law of diminishing returns applies to this trend, and each successive additional camp results in less change in the periods of stay and absence.
The changes in periods of stay and absence are substantial with increasing camp numbers up to about eight camps, but thereafter additional camps have a very small effect on the length of these periods. Whichever factor is kept constant, the effect of increasing camp numbers on the other factors follows a similar trend. This leads to the conclusion that any advantages in exceeding 8 camps are questionable (Booysen, et al., 1974).
In determining the optimum number of camps per herd, it is the actual values of the cycle length, period of stay, and period of absence, rather than the trends, that are important. Suitable cycle lengths range from approx-imately 40 days in sourveld to approximately 80 days in sweetveld. With only two camps per herd, the period of stay is long enough to permit regrazing within the period, and again at an interval close to the period of absence (Table 1). With three camps, the situation is greatly improved, although some regrazing may still occur within the period of stay, particularly with a long cycle length of 80 days. With additional camps the position is further improved, and at the level of six camps per herd the POS is short enough to ensure that regrazing within the period will not occur to any significant extent, unless the stocking rate is excessive (in sweetveld there is less tendency for regrazing to occur than in sourveld, and a longer period of stay is tolerable). From this point, therefore, little will be gained by adding further camps in order to reduce further the period of stay.
When no regrazing occurs within the period of stay, the interval between defoliations in successive periods will approximate the cycle length, which remains constant if the stocking intensity (AU grazing days per ha per period of stay) is constant. There is, therefore, also likely to be no benefit in terms of increased interval between defoliations with further addition of camps.
NUMBER OF CAMPS FOR ROTATIONAL GRAZING AND RESTING
It is apparent that rotational grazing with approximately six camps per herd should permit very good control of defoliation. In veld in good condition, reasonable control of defoliation, at least as an interim measure, may be possible with as few as three camps in sourveld, or four camps in sweetveld. In sourveld, one third more camps are needed to provide a rest and burn once in four years, giving a total requirement ranging from a minimum of four to a possible optimum of eight camps. In sweetveld in good condition, an 80-day cycle provides adequate rest within the rotation, so a total of four to six camps should be adequate. Sweetveld in poor condition may require additional full-season rests once in approximately four years, which would increase the required number of camps up to five to eight camps per herd. This number of camps would also be desirable where burning for bush control is necessary. The number of camps required in mixed veld is similar to that for sourveld, but a longer cycle length (approximately 55 days) and longer periods of stay and absence would be applied.
It is possible to make reasoned deductions as to the adequate or optimum numbers of camps per herd to
achieve various objectives. However, the benefits of increasing the numbers of camps in terms of animal production are not known at this stage. It is therefore not possible to calculate the economic optimum number of camps per herd. In the short term, individual animal performance can, at best, be expected to remain constant with increasing numbers of camps per herd, provided the stocking intensity is kept constant (Denny & Barnes, 1977) by reducing the period of stay in proportion to the increase in the number of camps (refer to Production Guideline 8.1 in this series). Any economic benefit must, therefore, come from an increase in carrying capacity, due to more favourable defoliation and any other possible beneficial effects.
Table 1. Relationship between number of camps and periods of stay (POS, in days) and absence (POA, in days), with various grazing cycle lengths.
Number of camps
Cycle length
40
55
80
POS
POA
POS
POA
POS
POA
2
3
4
5
6
7
8
12
16
20
30
20.0
13.3
10.0
8.0
6.7
5.7
5.0
3.3
2.5
2.0
1.3
20.0
26.6
30.0
32.0
33.3
34.3
35.0
36.6
37.5
38.0
38.6
27.5
18.3
13.8
11.0
9.2
7.9
6.9
4.6
3.4
2.8
1.8
27.5
36.7
41.2
44.0
45.8
47.1
48.2
50.4
51.6
52.2
53.1
40.0
26.7
20.0
16.0
13.3
11.4
10.0
6.7
5.0
4.0
2.7
40.0
53.3
60.0
64.0
66.6
68.6
70.0
73.4
75.0
76.0
77.4
The economics of increasing the number of camps per herd will vary in different situations according to:
- the cost of fencing and water provision;
- whether the farmer's or borrowed capital is used;
- the interest rate and redemption period of borrowed capital;
- the marginal tax rate of the farmer;
- the net farm income (NFI) achieved per AU;
- the size and initial carrying capacity of the area; and
- the increase in carrying capacity that can be achieved through an increase in the number of camps.
The cost of development varies according to the shape of the area, the topography, the type and layout of fencing, and the extent to which additional water points have to be provided. A rectangular camp layout requires least fencing, while wagonwheel and triangular layouts require more fencing but less additional water development (York & Gammon, 1975).
With so many variables involved, it is only possible here to provide a simple illustration of the economic considerations in increasing the number of camps per herd. Table 2 shows, for a square 400 ha area, with a central water point, the additional fencing and piping required to form two, four, eight or sixteen camps with a rectangular layout. The cost of additional development is based on 1989 costs, and will obviously increase with inflation. However, if the NFI/AU keeps pace with increased costs, the indications of this table could remain relevant.
The additional carrying capacity that would be required to justify or pay for the extra camps will vary according to the way in which the development is financed. If the farmer uses his own capital, he may be satisfied simply to realise the same return on this investment as he is already realising on his existing investment in livestock production. In this case, a 10% return on investment would be a generous expectation for most beef enterprises. Justification for the investment would be that turnover is increased, while the veld is conserved or improved. The last column in Table 2 provides the increased carrying capacity in AU’s that would be required at each level of development to realise 10% return on the extra investment, including the cost of the additional AU’s at R1 000 per AU, assuming a NFI of R200/AU.
If money has to be borrowed for the investment, the interest rate and redemption period are critical. For example, if money is borrowed at 15% over a 10-year period, requiring repayment of R200 per annum per
R1 000 borrowed, each extra AU run will only just pay off the investment in itself (assuming a NFI of R200/AU), leaving no surplus to pay off the development costs. However, such development qualifies for financial assistance, currently at 8% over 20 years, requiring repayments of approximately R100 per annum per R1 000 borrowed. In this case, the increases in carrying capacity required to repay the loan are the same as those required for 10% return on investment (Table 2).
The percentage increases in carrying capacity required to cover the cost of increasing camp numbers will vary with the initial carrying capacity. For example, if the area initially carries 100 AU (4 ha/AU), the additional AU’s in Table 2 represent the required percentage increases in carrying capacity. With higher initial carrying capacities, the required percentage increases would be proportionally lower, although this trend would tend to be countered by lower NFI/AU in higher carrying capacity sourer veld.
The converse would apply to veld with lower carrying capacity. Development costs are legitimate tax deductions, and, as such, the effective cost of development can be greatly reduced, depending on the farmer's marginal tax rate. Similarly, the cost of additional animals can be effectively reduced as they reflect a loss at book values.
In practice, instead of increasing stock numbers with purchased animals, it might be preferable to retain extra heifers from the breeding herd. In this case, taking account of the initial loss of income, borrowed capital for development could be paid off in approximately the same period as in the case where extra animals are purchased.
Table 2. Development costs for camping a 400 ha square area and increased carrying capacity required to yield a 10% return on additional investment, or repay a loan at 8% over 20 years.
Number of camps
Camp size (ha)
Additional fencing (km)
Additional piping (km)
Cost of additional development 1
Additional AUs to cover increased investment 2
1
2
4
6
8
16
400
200
100
67
50
25
-
2
4
6
8
12
-
-
-
0.7
1.0
2.8
-
R4 000
R8 000
R13 500
R17 900
R28 900
-
4
8
14
18
29
1
Fencing at R2 000/kmPiping at R1 300/km
Water troughs at R300 each
2
Including cost of R1 000/AUAssuming Net Farm Income of R200/AU
The economics of increasing numbers of camps will vary greatly in different circumstances. However, in most cases the increases in carrying capacity required to cover the cost of development to the level of 4 to 8 camps would be modest and should be attainable.
LITERATURE CONSULTED
BOOYSEN, P. DE V.; KLUG, J.R. & YORK, B.S. 1974. Number of camps for rotational grazing of veld. Proceedings of the Grassland Society of Southern Africa 9 : 145 - 148.
DENNY, R.P. & BARNES, D.L. 1977. Trials of multipaddock grazing systems on veld. 3. A comparison of six grazing procedures at two stocking rates. Rhodesia Journal of Agricultural Research 15 : 11 - 23.
GAMMON, D.M. 1969. Some economic aspects of veld management systems. Proceedings of the Veld Management Conference, Bulawayo. pp 113 - 120.
SAVORY, A. 1978. A holistic approach to ranch management using short duration grazing. Proceedings of the 1st International Rangeland Congress, Denver, Colorado. pp 555 - 557.
YORK, B.S. & GAMMON, D.M. 1975. An evaluation of methods of paddock development.