Last update: April 3, 2012 09:41:43 AM E-mail Print

 

THE FEEDING VALUE OF OUR NATURAL PASTURES

 

Willem Loock

 

The extent to which the veld on a farm can provide in the demand of animals with respect to protein, energy, minerals and vitamins determines the feeding value of that veld. Since veld always have been the cheapest source of feed, it is important that we should be acquainted with any possible deficiencies, excesses or imbalances which might occur in the veld during certain times of the year.

Deficiencies and/or imbalances are to be determined and the necessary corrections brought about by supplementary feeding in some form or other. Several other factors must be considered before supplementary feeding can be recommended.

The nutritive value of the veld is influenced by the digestibility, the voluntary intake and the chemical composition of the plants occurring in the veld. At present we only have the chemical composition, but in the evaluation of the nutritive value of the veld the shortcomings should be borne in mind. Recommendations depend to a large extent on intelligent interpretation of available information.

The chemical composition of plants which generally occur in the different veld types of the Pearston, Graaff-Reinet and Aberdeen districts, is indicated on the opposite page. In Table 1 the average values of plant species are used and include palatable as well as unpalatable species. The values are given in green (G) as well as dry (D) stages of the plants. The grasses and "opslag" are combined while the values for bushes and shrubs are given individually.

Notwithstanding the fact that the protein content of grasses is much lower during the dry stage than the green stage, it also is remarkable that the protein content of these plants increases from mountain to slope to leegteveld. The high protein value (23 percent) of leegteveld during the green stage can mainly be ascribed to "opslag" which have a relatively short growth cycle and are thus only present in the veld for a short period.

In the case of bushes and shrubs the protein content is also higher on leegteveld than on mountain veld, although a smaller variation between green and dry stages exist as is the case with grasses.

If a protein content of nine percent is stated, it is found that mainly the grasses do not comply to this requirement, especially during the dry period. Where the veld mainly consists of dry winter grass, better utilization of the dry material ought to take place when protein is supplemented. The protein content of winter-grass veld could decrease to such a low value as to be insufficient for maintaining the physical requirements of the animal (Suurpol). This concentration is often unable to supply in the nitrogen requirements of the rumen organisms, with the result that digestion of the pasture material is lowered, the rate of passage retarded and intake decreased, - the effect on the animal being a serious shortage of energy.

The fibre content of a ration or a plant is an indication of its digestibility. An increase in the fibre content results in a lesser degree of digestibility. If it is kept in mind that the ideal roughage has a fibre content of at least 23 percent, the fibre content of the grasses in Table 1 is particularly high. This indicates that the grasses are generally less digestible on this particular type of veld.

It would appear that mainly protein energy, and in some cases phosphate, is giving problems, especially during the dry period of the veld. Therefore, farmers should mainly concentrate on the supplementation of energy, protein and possibly phosphate.

 

 

 

Published

Karoo Regional Newsletter December