- Food value of Karoo shrubs. Part 7
|Last update: April 5, 2012 08:00:28 AM|
FOOD VALUE OF KAROO SHRUBS
E. E. BUTTNER
GROOT KANKERBOS (SutherIandia Microphylla)
THIS is one of the finest of our Karoo shrubs so far as sheep are concerned. In fact it is very much favoured by them and they will do anything to get into a patch where this shrub grows. Probably it is the high protein content that attracts the animals most but the plant is very well balanced on the whole as far as minerals are concerned, except that the calcium (lime) content is rather high for veld where the sheep already get plenty of lime in their water or other food growing on the veld. Even in droughty conditions Groot Kankerbos will, if well represented, enable the sheep to do remarkably well. However, when the bushes are very small and young, the carrying capacity is only about one and a quarter sheep per morgen. Nor is the shrub a producer of body weight to any great extent. This is probably because it only produces muscle instead of body fat.
Looking at the plant from the point of view of the analytical chemist it seems better balanced than all the other Karoo shrubs studied so far. The ratios between the mineral elements are excellent, except for its high calcium content. The total mineral content is quite high compared with many another Karoo shrub. The magnesia content is just about right, especially where the presence in drinking water is high. The potassium is also in the right proportion as compared with the sodium content, for the latter is just about as high as the former, so that sheep grazing on this shrub to a great extent require no salt in their licks. In fact, a salt lick would upset the potassium:sodium balance. The phosphorus content is quite fair, and so is that of sulphate.
Seeing that the chloride content is fairly low one wonders in what combination the calcium occurs. If the plant is rich in oxalic acid, like the various vygies, then the high calcium content will be taken care of so that it cannot exert the effect of an excess either way, of calcium or oxalic acid, inside the animal body, but will then be excreted as insoluble calcium oxalate with the droppings, at least to a great extent.
KLEIN KANKERBOS (SutherIandia Humilis)
Looking at the chemical analysis of this shrub there is practically no difference between this plant and the previously mentioned one, except that the protein content of the Klein Kankerbos is a little lower, which also seems to apply to the fat and fibre content. However, the silicon content of the latter is higher, although not as high as in some of the other Karoo shrubs. The silicon content is of greater importance to sheep than to any other farm animal because it is a vital element in the composition of high quality wool, making it springy, full of life and durable as well as healthy looking. The sodium content is higher than in the previous plant, so that a salt lick is even more superfluous here than in the case of Groot Kankerbos.
Looking at the moisture content of the two shrubs mentioned here it would seem that they are more resistant to drought during the dry months than several of our other. Karoo shrubs. Of the two shrubs Klein .Kankerbos contains the smaller percentage of fat, but this is made up for again by its higher carbohydrate content, which produces and conserves body fat under favourable conditions of nutrition.
BERG GANSIE OR GROOT BERG GANSIE (Pentzia Sphaerocephala)
his valuable fodder plant occurs only on hills, mountains and stony outcrops. It is a large flowered Pentzia not easily confused with the other Pentzias. Cattle and sheep alike graze the plant very well, which speaks a lot on its behalf, not only from the point of view of palatability but also because of its dietetic value, or even food value. For even very bitter plants are sometimes preferred to sweeter ones if the latter's food value should be low.
The protein content of this shrub is generally quite low. This is because it is sensitive to lack of rain, for in wet months the protein content will jump up to double the normal content. It is thus only just after good rains that the protein content will reach the value of 20 per cent. But most of the year the value remains more or less constant at about half that figure. Plants not grazed for several years will of course contain rather low protein values owing to high fibre content. But the ordinary winter, even with heavy frosts, will not tend to reduce the protein content appreciably.
The total mineral content is not very high, but yet not to be despised by any means. The silica content is about similar to that of the Kankerbossies. This is fair. The fat content is however higher and at most of the year appreciable. This explains the fattening properties of the shrub when in good condition. The weight gains are due to fat rather than muscle production in the tissues. The fibre content is rather high, however, except in wet seasons. Even then it is not low by any means. The carbohydrate content is fair, which helps the animal to utilize its fat content economically. The calcium content is slightly lower than in the Kankerbossies, while the magnesium value is just as low. While the potassium content is quite low,. The value for sodium is very low indeed,. though higher than in the case of a grass. So it would be advisable to give animals grazing predominantly on this shrub a lick with salt, to balance the potassium of the shrub and that of the water if brak, through potash salts. But if the water contains sodium salts then the lick requires no salt additions. For most of the year the phosphorus content is rather low. Only after good rains will it be high and then only for a short period.
Sheep farmers are often puzzled as to which lick to give in the dry season. Generally they end up by giving one mostly composed of salt, molasses and perhaps a little trace mineral mixture. The point to bear in mind, however, is that what sheep need most for wool, flesh and fat consists of the same things they need for perfect health. In other words they need protein, carbohydrates and vitamins mostly under Karoo conditions. Minerals are often in excess especially potassium, calcium (lime), magnesium, sodium and also harmful minerals like nitrates and fluorides generally in the borehole water, but also in surface water. About the best of the cheaper supplements would be mealie bran, or wheat bran, mixed with molasses. This supplies protein, carbohydrates, vitamins and minerals as well as trace minerals. The molasses is the Source for the latter. In fact molasses is really only a carbohydrate, mineral and trace mineral source, with some valuable vitamins. But a lick of salt and molasses is deficient in protein, certain essential vitamins and in the vital fats found in bran oil. These oils contain vitamin E and the essential fatty acids that do so much for the health of the animal.
Merino Breeders Journal 26 (1)