Last update: November 30, 2010 03:42:07 PM E-mail Print




J.H. Hoon

Grootfontein Agricultural Development Institute

Middelburg, Eastern Cape, South Africa



Drought is possibly the greatest single factor that influences the economics of livestock production enterprises in South Africa. The fear of drought is the single most important factor that prevent stocking rates from approaching those theoretically possible, particularly on improved veld. Droughts can refer to periods of low rainfall following a ”good season” when pastures mature and dry off and the quality appears too low to support cattle and sheep production. They can also refer to periods of prolonged dry weather when the livestock has consumed the available pasture. Fire can also induce a drought overnight on an individual property.

Drought feeding strategies depend on the specific conditions prevailing in any particular area. In general the farmer has to make decisions based on economics, knowledge of nutrition, the availability of feed resources and his calculated guest on the length of the drought. The options may include:

Prediction of drought appears now to be more of a reality with the improved knowledge of the El Nino phenomenon. However, in the back of the mind of farmers there is a continuous, nagging recognition that drought is unpredictable and imminent. Therefore, the consequences of drought monopolises much of the thought that goes into the forward planning of a property particularly where drought situations are predictable, such as occurs with annual dry seasons. In South Africa, droughts can be classified in three categories:

  1. Protein drought – It is the same as a normal winter (or summer in the Western Cape) with sufficient dry veld (or stubble-fields). Protein is the only nutrient that is deficient.
  2. Protein and energy drought – It is the same as a normal late winter (or late summer in the Western Cape) when the quality as well as the quantity of veld (or stubble) are a problem.  Under these circumstances it is important that protein and energy are supplemented to prevent large mass and reproduction losses.
  3. Total drought – Total drought situations will vary between the normal late winter (of late summer in the Western Cape) situation and a disaster drought where no roughage from the veld is available. Cattle need to be helped earlier than sheep and goats, because the small stock utilise veld lower and more complete and also utilise shrubs and other plants more efficient. For the first phase of a disaster drought, it will therefore be cheaper to maintain sheep and goats.



There seems to be three major rules when considering a strategy for drought feeding (Leng, 1987):

  1. When a drought is present, if you have to think about what you are doing, you will be in no position to obtain the necessary resources to apply modern concepts. You have to know what you are doing and having planned it by thinking about what you will do next if the situation gets worse.
  2. The aim of a drought feeding strategy should always be to optimise the efficiency of utilisation of the available least-cost resource. This is nearly always dry veld early in a drought, but becomes more and more some form of supplementary feeding as available veld is reduced.
  3. When a drought is prolonged and pasture is virtually absent, or the animals have grazed as much as possible without excessive soil erosion occurring, then it is important to use combinations of supplements to optimise utilisation of the least expensive (in money and labour) feed resource.

The most important nutritional consideration for both cattle and sheep is to recognise that two systems must be fed at once:

The important point is that when ruminants are fed drought-based diets, the products of fermentative digestion are seldom balanced (in the quantities of individual and essential nutrients) to meet productive functions or even maintain body weight.

Because of the rainfall patterns in large parts of South Africa, it seems highly probable that there are few occasions throughout the year where the grazing animal obtains a sufficiently well balanced array of nutrient to maximise the efficiency of feed utilisation for a particular productive function. It could be speculated that it is only the suckling lamb with its mother on pasture that is ever supplied with sufficient bypass nutrients.

In very few instances do we wish to feed for maximum production in drought. In most situations we wish to use, as efficiently as possible, a restricted amount of feed to maintain animals or to feed for survival. With pregnant and lactating animals it is always necessary to feed for the maintenance of the foetus and for maintenance of a minimal milk production. Research projects in which animals are fed for maintenance, it has been illustrated that these animals are highly inefficient in utilising feeds if the nutrients available are not in balanced quantities. The effect of feeding the animal extra urea/sulphur and bypass protein respectively on low digestibility roughage diets (45% digestible, 3% protein) is illustrated in Table 1.


Table 1. The effect of protein feeding on hay intake and production of growing or pregnant cattle (Leng, 1987)


Intake (kg/day)

Live weight change (kg/day)

Growing cattle (170 kg live weight)



Urea/sulphur bypass protein (500g/day)









Pregnant cattle (last 60 days)



Urea/sulphur bypass protein (1kg/day)









The results presented in Table 1 indicate the principles of ruminant feeding which involves providing nutrients for two systems (i.e. the rumen organisms and the animal. When the ruminant is deficient in nitrogen or sulphur (or any growth factor), microbial growth efficiency in the rumen is low.


Balancing nutrients in the animal

If the absorbed nutrients are imbalanced relative to the animal’s needs, then the animal must adjust these nutrient balances. As the largest proportion of feed is converted in the rumen and intestinal tract to non-glucogenic substrates, then the likely imbalance will always tend to be the availability of acetogenic VFA (acetate and butyrate) to glucogenic substrate (largely propionate) and essential amino acids. The animal has little option but to either wastefully oxidise (in futile circles) the acetogenic substrate (burn off), or it may decrease its feed intake. If the amount of extra heat generated is similar to that produced in fasting animals over and above basal metabolic heat, this would mean that 30% of energy in a diet is lost in wasteful cycles of metabolism due to an imbalanced nutrient supply (or in practical terms due to lack of sufficient bypass protein in a diet). A heat load due to the oxidation of 30% of the nutrients absorbed would impose a critical heat load in animals at high environmental temperatures or moderate temperature and high humidity. It would, however, impose little stress on animals at low ambient temperatures, and may even be beneficial, as the heat would be used for maintenance of body temperature (Leng, 1987).

This emphasises that ruminants in the hot or the hot-humid tropics require different approaches to feeding methods and standards. More importantly, however, is that there is a large potential reduction in total feed requirements for maintenance of animals when nutrients are balanced. Balancing diets for ruminants in supplementary feeding situations will result in animals in much better condition at the end of the drought, because they use the available feed more efficiently. 


Hints for feeding during droughts

Which animals to sell

Old animals, animals with poor reproduction records, heifers or young ewes which did not calved/lambed, oxen/wethers. Culled animals can be fattened profitable with own-produced maize or other grains

Roughage vs. concentrates

In times of drought, roughage is scarce and often very expensive. Research has indicated that animals can survive more successful and more economical on concentrate-rich ingredients. Disadvantages of roughages are much higher transport cost, higher cost per unit utilisable energy, more losses during feeding and also a higher fire hazard.

Frequency of feeding

Research has indicated that animals receiving daily survival diets, performed poorer and had a higher mortality rate than animals that had been fed twice or just once a week. With daily feeding, some animals ingest more than their share while others get nothing, starve and eventually die. When more feed is supplied at once, but less frequent, each animal has a better chance to receive its part of the diet.  

Early weaning

Early weaning of both lambs and calves is a strategy that can be used to save costs and to utilise scarce feed resources more efficiently. The best examples of such feed sources are creep feeding or cultivated pastures. Early should, however, not be considered if high quality green fodder or concentrate-rich mixtures are not available. Early weaning reduces stress on cows and ewes, which can then be fed cheaper ingredients. Creep feeding has the following advantages:


How much to feed

This will depend largely on the amount of veld available. If there is no grazing available, research results have shown that beef cows with an initial body weight of 440kg, can be kept on a 3.6kg concentrate-rich daily diet for eight months, with a weight loss of only 63kg. This converts to a total TDN-intake of 2.65kg. Sheep on the other hand need a TDN-intake of 265g when concentrate-rich diets are supplied, and 365g TDN in the case of roughages like lucerne.


Weight loss

The rule of thumb is normally that supplementary feeding should start before animals have lost more than 15% of its normal mature body weight. If animals are allowed to lose weight slowly and systematically, they will, however, be able to stay healthy on survival diets during droughts at 66% of their normal mature body weight (cattle - 500kg down to 330kg; sheep – 50kg down to 33kg). This rule does not apply to pregnant animals because large weight losses can lead to abortions.


Treatment of low quality roughages

The utilisation of cereal straws is very important for animal feeding in the Western Cape during the dry summer months. Chemical treatment of low quality roughages to improve digestibility has been practised for many years in South Africa. The process most commonly used is NaOH treatment, which hydrolyses ligno-cellulose bonds, resulting in increased digestibility. In vivo studies show an optimum treatment level of 4% NaOH on a dry matter basis and further improvement in animal performance can be obtained by the inclusion of bypass protein in the diet. A limitation of NaOH treatment is the additional energy required by the kidneys to excrete Na . This has led to the development of ammoniation (NH3 treatment) as a method of upgrading low quality roughages.  Results with the ammoniation of low grade roughages have indicated an increase in metabolizable energy of 1.3 MJ/kg DM, while one ton of treated maize stover was equal in feeding value than 1.2 ton untreated stover plus 17kg urea. (Meeske, 1992). The first recognisable change in cereal straw treated with NH3, is a change in colour  (browning or caramelisation) as a result of the Maillard reaction between carbohydrates and N-containing bonds.  Although very seldom, a problem does sometimes occurred during the process of ammoniation with the formation of a toxic compound, 4-methyl-imidazole, which can lead to animal losses (Vosloo, 1985).


Drought fodder crops

The most important single factor limiting plant production in South Africa, is the lack of sufficient moisture. Increased plant production in these areas is thus coupled to factors which will either increase the amount of moisture or make better use of it. The most important possibility thus remains the establishment of drought fodder crops which make better use of the available moisture. The most important drought fodder crops in South Africa are oldman saltbush (Atriplex nummularia), spineless cactus (Opuntia spp.) and American aloe (Agave americana). The relative water consumption of drought fodder crops in relation to other crops is indicated in Table 2.


Table 2. The relative water consumption of different crops (De Kock, 1980)


Kg water required to produce 1 kg of dry material

American aloe


Spineless cactus


Oldman saltbush


Fodder sorghum









Requirements of a drought fodder crop


Oldman saltbush (Atriplex nummularia)

 Oldman saltbush is a perennial shrub, indigenous to Australia, and has been found in South Africa for the past hundred years. Oldman saltbush can be grazed from the second season after establishment. When saltbush is grazed, sufficient drinking water must be supplied, as the sheep becomes thirsty from the salt in the plants. If the drinking water is also very brackish (high total salts content), an adaptation period of two to three weeks should be allowed for animals to adapt to the very high total salt intake. After this adaptation period, feed intake and animal performance are the same as animals receiving fresh water (King et al., 1991). Apart from the drought resistance, a noteworthy characteristic of these plants is their high production of green succulent feed under relatively poor moisture conditions. An indication of the amount of edible material per hectare produced by oldman saltbush is given in Table 3.


Table 3. The yield of leaves of oldman saltbush (De Kock, 1980)


Dry mass (ton/ha)

Green mass (ton/ha)






















The results in Table 3 also illustrate the ability of oldman saltbush to recover after defoliation each year. This is one of the reasons which make this crop exceptionally suitable as a grazing crop. A carrying capacity of 21.74 sheep per hectare for four months of the year was calculated for oldman saltbush (2500 plants/ha), which converts to a carrying capacity of 6-8/sheep/ha/year). An average number of 2800 sheep grazing days per ha of oldman saltbush per year was obtained at Grootfontein A.D.I. (De Kock, 1980). Similar values were calculated from the results obtained by Hoon & King (1992).  Oldman saltbush is high in protein (16-22%) and can supply the maintenance requirements of sheep. It can also maintain ewes during late pregnancy and lactation, but for optimum production and reproduction, additional energy should be supplemented.


Spineless cactus (Opuntia spp.)

Spineless cacti possess the exceptional characteristics of being able to store large quantities of water in their succulent leaves in a relatively short period. Just a few millimetres of rain which would normally be of no value to ordinary fodder crops, can be utilised efficiently by this plant. Spineless cactus is not only of value as a source of succulent fodder during droughts but can also be used in the reclamation of bare patches and in the conservation of veld. Spineless cactus is deficient in protein (3-4% on DM basis), while the high moisture content (about 90%) is a factor that limits intake. Even for maintenance of animals, it is necessary to supplement spineless cactus with one or other form of protein. The method of utilisation of spineless cactus will differ from farm to farm according to circumstances such as available labour, facilities, quantity available, etc. The different utilisation methods are the following:


American aloe (Agave americana)

American aloe is one of the hardiest plants which can be established for the production of fodder in the arid and semi-arid regions. American aloe has the same deficiencies as spineless cactus with regard to nutritional value, namely a high moisture (85-90%) and low protein (3-4%) content. Like oldman saltbush and spineless cactus, the growing season of American aloe plants is in the summer months. In the autumn and dry winter months the leaves can be processed (chopped and chaffed in pieces) and fed to animals. A yield of 120 tons of leaves per hectare can be expected annually from American aloe, even on relatively poor soils (De Kock , 1980). An extensive study on the utilisation of American aloe as a feed source for sheep at Grootfontein A.D.I. has indicated that American aloe leaves were able to satisfy 64% of the maintenance requirements of mature sheep, but that the best results were obtained at an inclusion level of 45% in maintenance diets. It was concluded that the most important applications of American aloe would be as a survival diet (e.g. during serious drought conditions) or as a major component of a maintenance diet. (Hoon, 1994).


Livestock feeding in the developing agriculture

Leng (1991) states that livestock in developing areas are mostly restricted in their nutrition to:

Apart from a general shortage of feed stuffs, the feeds that are available are fibrous and relatively high in ligno-cellulose. They are usually of low digestibility and are often deficient in critical nutrients, including protein, non-protein nitrogen and minerals. Generally, the forages consumed by ruminants in developing areas are almost always below 55% (usually 40-45%) digestibility and often have less than 8% crude protein, the protein level more often being around 3-5% (Leng, 1991). The net result of livestock farming under these conditions is an extremely low rate of productivity, being 0.1-0.25 of that of ruminants in the temperate countries grazing fertilised pastures of fed high-quality feeds based on grain and immature pasture plants.  

Research has a key role to play in ensuring that animal production supports economic growth in Sub-Saharan Africa. As a result of the high population growth rate, land will become more limited particularly due to pressure for better crop/grain production. Consequently, opportunities for livestock development will increasingly necessitate technological change that includes more productive animals which are managed and fed better. Research will have to play an increasing role if higher and sustainable animal productivity is to be achieved (Henning, 1995).

Leng (1991) proposes a list of research priorities for animal nutrition in the developing areas:


Feed technologies

-          development of appropriate supplements of mineral, non-protein nitrogen and other microbial factors

-          identification of  protein resources naturally protected from rumen degradation

-          processing of protein resources to protect them from rumen degradation.

-          protein from crops, trees, by-products

-          aquatic plants, algae and animals.


Manipulation of digestibility

-      modification of the ecosystem

-      addition of modified organisms


Manipulation of metabolism within the animal

A comparison of the above list or research priorities with the review of ruminant research done in South Africa over the decade actually suggest that a large part of the research done locally during the decade 1985/1995 (although mostly on behalf of the commercial sector) is actually applicable to livestock farming in the developing areas. It can be argued that it is actually incorrect to discern between research for established or commercial agriculture and for emerging agriculture, since there is practically no technology, especially in the livestock sphere, which is not equally applicable to both. There is, however, a lack of compatibility between technology and the actual farming systems in the developing areas. There is also a lack of technology transfer linkages which inhibits the development of appropriate farming systems in a participatory manner  (Henning, 1995). 



The main lesson to be learned from a drought situation is to remember that the next drought is inevitable and drawing closer. The major questions to be asked by farmers before it arrives, are:

What lessons have I learned from the last drought?

What is my strategy for the next drought?

Should I be looking for alternatives to traditional feeding strategies?

Is it possible to drought-proof my farming enterprise and what infrastructure should I develop?

How do I optimise the use of the available resources in the next drought and how can I be sure that I will be in a position to use this strategy?

The key is maximising the efficiency of drought feeding strategies by balancing the nutrients available to the animal for productive purposes



De Kock, G.C., 1980. Drought resistant fodder shrub crops in South Africa. In: Browse in Africa. Ed. H.N. le Houerou, p. 399-408.

Henning, P.H., 1995. Research to meet the needs of the small-scale farmer. Proceedings of Symposium “Recent developments in ruminant nutrition”, 18 October 1995, p. 111-123.

Hoon, J.H., & King, B. R., 1992. Determination of the voluntary intake of oldman saltbush (Atriplex nummularia) in three different forms. Karoo Agric, Vol.4, No.4, p.4-6.

Hoon, J.H., 1994. The ulilisation of Agave americana L. (American aloe) as a feed source for sheep. M.Sc. Agric.-dissertation, University of the Orange Free State.

King, P.R., Hoon, J.H. & King, B. R., 1991. The effect of brackish water on the intake of Atriplex nummularia (Oldman saltbush). Proceedings 30th congress of SASAP, Port Elizabeth (26-28 March 1991).

Leng, R.A., 1986. Drought feeding strategies: Theory and practice. Penambul Books, N.S.W., Australia.

Leng, R.A., 1987. Some theoretical consideration on drought feeding recommendations. In: Recent advances in Animal Nutrition in Australia – 1987, p. 104-111.

Leng, R.A., 1991. Application of biotechnology to Nutrition of Animals in Developing Countries. Paper No. 90. Food and Agricultural Organisation of the United Nations, Rome.

Meeske, 1992. Improving the feeding value of low quality roughage. Proceedings of the Highveld Branch of SASAP, Vol. 13, p. 23-30.

Vosloo, L.P., 1985. Roughage feeding of ruminants – new developments. S. Afr. J. Anim. Sci., 15 (3) p. 86-90.