Farmer's Weekly (South Africa)
Valuable but dangerous
This exotic shrub can be used as feed during drought. But beware – it’s a highly invasive pest plant. For the most part, mesquite is bad news for farmers. It can become an uncontrollable menace. Yet farmers in the Northern Cape, forced by drought to seek alternative stock feeds, are feeding the pods to small stock.
Milled mesquite pods have a feed value of about 85% that of maize. They have 11,7% digestible protein, 71,6% total digestible nutrients and 26,3% fibre. So, 850 of the milled pods daily will supply enough nutrients and protein for a 60kg sheep.
However, mesquite, (muskietboom or Suidwesdoring) tends to spread easily and become a nuisance, especially in the dry arid areas of the Cape. Therefore the seed should only be propagated under strict supervision, with careful consideration given to the fact that if it cannot be confined to its allocated site, eradication will be costly and difficult.
Also, if the plant becomes uncontrollable it can acquire local weed status, posing a threat to the undisturbed natural flora.
Mesquite is a spiny, thicket-forming shrub from north-eastern Mexico and the south-western US. Because of its tolerance to frost and drought, mesquite has become well established in the Kenhardt area and other dry regions of the Northern Cape.
Fifty-five years ago four of these trees were planted on Dr Kraai van Niekerk’s farm, Rugseer, near Kenhardt, by his father-inlaw, Dr Ryk Claasens. Today there are about 400ha of mesquite, propagated mainly by the seeds spread in animals’ droppings.
CONTROLLING MESQUITE
For mesquite to be controlled, the pods must be collected before domestic or wild animals can get to them. This means limiting the number of trees and employing an efficient labour force that can manage the fallen pods.
The seed pods must also be broken or milled otherwise they retain their nutritional value. Another reason is that they are quite resistant to the acidic stomach juices of animals, an advantage for propagation as they pass through to the droppings undigested.
If the pods are to be fed to animals without being milled it is a wise idea to keep the animals in a small camp. Propagation of the seeds will thus be limited, and seeds that do germinate can be removed by hand.
However, the animals will not get the full nutritional benefit from the pods. Wild animals also relish the pods and spread the
seeds to the uninfected veld. Porcupines are a particular problem, says Van Niekerk because they eat the pod material only, so the seed coat remains unbroken and the seed viable.
Frikkie Steyn, who manages Van Niekerk’s farm, says mesquite pods are collected by workers and packed into sacks. They are paid in relation to the amount of sacks filled and get a bonus for every sack above 100 that they fill. This gives them an incentive to work faster and also curbs the mesquite propagation.
A large tree produces up to 90kg (wet mass) of pods a year and in ideal conditions a top tree can produce 140kg annually.
At Rugseer, the pods are stockpiled in heaps that are contained by wire fencing. When necessary they are passed through a hammer mill with a 3mm sieve.
LIVESTOCK FEED
Sheep relish the pods due to their sweet taste and high sugar content. To prevent souring in the rumen, 2kg of agricultural lime is added ȱ¢ȱśŖȱȱȱǰȱȱ ȱȱŗȟȱȱ water (to counteract the dustiness of the lime) and 2kg of salt. At Rugseer the milled pods are fed 50:50 with lucerne and/or maize meal.
The pods and other constituents are mixed in a modified drum which is turned by hand. Vanes inside the drum give a mixing action similar to that of a cement mixer.
During storage the milled material may form small cakes because the warmth causes any remaining moisture to evaporate. It is therefore important to break up the chunks by hand when the mixture is fed, says Steyn.
Control of the mesquite trees is vital, difficult and expensive. A mixture of picloram (Tordon) and diesel is sometimes sprayed. This method costs R40/ha to R50/ha (about R580 to R700 today).
Steyn says a cheaper method is to remove the trees a few at a time by hand but this is time-consuming. The tree must be removed with as much of the root as possible, otherwise it will grow back. The wood is then used for domestic fires by the farmworkers.
The mesquite pods are nutritional and may be an alternate stock feed but the trees’ encroachment must be tightly controlled.
Research is being done at Rugseer by the Department of Agriculture to refine methods of control for this recognised invader.
This article first appeared in the
3 October 1986 issue of Farmer’s Weekly and has been edited to adhere to the current style of the magazine.