Estimated reading time: 8 minutes
- The first prickly pears arrived in South Africa shortly after Jan van Riebeeck’s tenure in the Cape, but it was not until the 1960s that this cactus was recognised for its use as an emergency drought fodder crop. These days a number of producers successfully include prickly pears in their fodder flow planning.
- The sixties saw quite a few extreme droughts and the then Department of Agriculture put a lot of effort into identifying effective drought fodder crops and encouraging producers to cultivate them. The most commonly cultivated thornless prickly pear cultivar was the so-called spineless cactus pear, Opuntia robusta.
- Different utilisation options were studied, such as feeding whole leaves, chopping the leaves, drying the chopped leaves for inclusion in rations, and even silage production.
- Two distinct lines have developed over the years: fruit cultivars that yield large numbers of fruit, and fodder cultivars that are highly productive in terms of leaf yield. In-between these are the so-called dual-purpose cultivars that yield a fair amount of fruit and leaves. Choosing the correct cultivar for the intended goal is therefore vital.
The first prickly pears arrived in South Africa shortly after Jan van Riebeeck’s tenure in the Cape, but it was not until the 1960s that this cactus was recognised for its use as an emergency drought fodder crop. These days a number of producers successfully include prickly pears in their fodder flow planning. This is according to Dr Herman Fouché, an agricultural researcher who, until his retirement three years ago, researched prickly pears while at the Agricultural Research Council (ARC) in Bloemfontein.
The sixties saw quite a few extreme droughts and the then Department of Agriculture put a lot of effort into identifying effective drought fodder crops and encouraging producers to cultivate them. The most commonly cultivated thornless prickly pear cultivar was the so-called spineless cactus pear, Opuntia robusta. Around 25 years ago, renewed interest in prickly pears sparked research into whether the plants could be used more economically, especially in terms of fruit production.
Dr Fouché says this quickly led to the realisation of the incredible yield potential well-tended prickly pears can have. This resulted in attention shifting away from prickly pears as simply drought feed, to alternative feed uses that can be incorporated into fodder flow planning.
Different utilisation options were studied, such as feeding whole leaves, chopping the leaves, drying the chopped leaves for inclusion in rations, and even silage production. The production of feed blocks from chopped prickly pears was another promising option. New projects are aimed at studying the possibility of protein enrichment through fermentation.
Fill the fodder flow gaps
“Prickly pears are incredibly adaptive. They grow in areas with an annual rainfall of 100 to 1 000mm,” says Dr Fouché. “They do, however, have two limitations: they don’t like ‘wet feet’, and they favour well-draining soil while disliking brackish soil. The only other downside is that severe cold – below 10°C – may affect it negatively.”
The potential benefits of prickly pears in dry areas are obvious. However, it is in the high rainfall regions in the eastern parts of the country, with its typical sourveld, that prickly pears can play a sizable role in filling fodder flow gaps.
“Prickly pears can serve as a fodder bank or as standing hay. The big advantage is that its quality doesn’t deteriorate in winter – a drop in fodder quality is a big headache for producers in the sourveld regions. Prickly pears are therefore an excellent source of nutritious green material amid a shortage of other greenery.”
Read more about prickly pears – a buffer against drought click here.
If you compare the chemical analysis of prickly pear leaves with the performance of the animals, it does not add up, he says. The performance is always better than expected.
“The sourveld region poses several challenges to fodder flow. However, prickly pears can play a big role in bridging feed gaps, especially in late winter and spring. The prickly pear is unaffected by seasonal drought and even in the midst of a severe drought, it not only survives but also produces, which no other crops can do. Once the drought has come and gone, the plant is almost immediately available for use.
“This makes the prickly pear an essential factor when it comes to coping with climate fluctuations. We have been observing seasonal shifts, with seasons sometimes arriving later and lasting longer. This makes spring and early summer a particularly trying time.”
Choice of cultivar
Two distinct lines have developed over the years: fruit cultivars that yield large numbers of fruit, and fodder cultivars that are highly productive in terms of leaf yield. In-between these are the so-called dual-purpose cultivars that yield a fair amount of fruit and leaves. Choosing the correct cultivar for the intended goal is therefore vital.
Regardless of the purpose of the cultivar, it is a mistake to think that prickly pears do not require tending, warns Dr Fouché. “Fertilisation, weed control, and even strategic water supply before flowering are essential for maximising the yield from a prickly pear stand. Prickly pears respond exceptionally well to nitrogen treatment. Trials to determine whether high levels of nitrogen are harmful to the plant have shown that it is not the case.”
The best usage of prickly pears
Although prickly pears may be used as standing hay, Dr Fouché does not recommend it. Livestock grazing can lead to excessive damage to the plants, not to mention the large quantity of material that goes to waste. The better option is to chop off the leaves and feed it to the animals in a designated place, he says.
“Some producers in Brazil allow their livestock to graze prickly pear stands but make use of electric wires to demarcate the grazing area. A specific stand of prickly pears is then fully utilised and afforded a two-year period in which to recover before being grazed again.
“The speed at which the plant recovers depends on its ability to photosynthesise. If you remove most of the cladodes you will impair the plant’s ability to recover. On the other hand, you will have quite a bit of plant material that you can feed to your livestock.
“If you follow our pruning instructions for fruit production, you’ll be able to use the plant every year. For producers who include prickly pears in their fodder flow planning, this approach is the most sensible. A plant such as this is ‘renewed’ every year and has an unlimited lifespan.”
The taller a plant grows, the less productive the leaves further down the trunk become. This must be taken into consideration when pruning the plant.
“We don’t allow our prickly pears to grow taller than 2m. These plants will yield a good 180 cladodes at a time. This amounts to approximately 144kg of wet material per plant, and for a stand of 1 000/ha this comes to a wet yield of 144t, or 14t dry matter (DM) per hectare.”
Nutritional value of prickly pears
Prickly pears, says Dr Fouché, are a source of energy with a low crude protein content. The protein content of optimally fertilised prickly pears can be as high as 8% on a DM basis. This means some source of protein must accompany the prickly pears when it is fed to livestock.
With regard to DM energy, the value ranges from 6 to 7MJ/kg – compared to the approximately 12MJ/kg of maize – with a crude fibre content of approximately 15% on a DM basis.
The issue of mucilage, warns Dr Fouché, is something to bear in mind when feeding prickly pears to especially sheep. The manure of sheep that are given a ration containing a high percentage of prickly pears will be very wet, so much so that it resembles diarrhoea. However, it is the mucilage in the prickly pear leaves that is responsible for this wet manure. The gut does not break down the mucilage; instead, it binds with water to the extent that it cannot be absorbed from the intestinal tract to form typically dry sheep manure.
Livestock must not be fed prickly pears alone. A good rule of thumb is 60% prickly pear and 40% dry forage, whether hay or veld.
Pest control
Two pests, cochineal and cactoblastis, were introduced to bring wild prickly pears under control and are still the biggest threat to a prickly pear stand. Good monitoring and control using a high-pressure sprayer are essential, says Dr Fouché, otherwise especially cochineal can destroy an orchard within two years.
The potential of prickly pears to play a more prominent role in livestock production, despite the threat of pests, is still being undervalued and Dr Fouché believes it should enjoy more attention. – Izak Hofmeyr, Stockfarm
For more information, phone Dr Fouché on 082 652 9532.
