The rest of the scheme dealt with a mineral survey of the Union pastures. The division of the country into eighteen zones 1ras macle mainly on the basis ·of the .Jiap Botany of '(Tnion of South Africa (Pole-Entns, 193G). Vegetation map of South Africa showing the division into zones for the purpose of discussion of mineral content and nutritional value of natural pastures.
The differences in the phosphorus and protein content of the pastures in the 18 different areas are most pronounced between the areas examined as "grassland" and the areas where shrubs predominate in the pastures. In the latter areas, the phosphorus content of the meadows fluctuates between approximately 0.12 and 0.20 per lease. Moreover, the low values in the grass meadows persist for a significant part of the year.
A study of the average phosphorus and protein values for each of the 18 areas separately reveals differences in pasture quality not only between the two main groups "women" and. The position I'a with regard to the content of phosphorus and proteins of samples hom Zones 9, l l and12 is not better than thnt in, for insh111re, They are:1 7. The superiority of the Sllll'ub desert to the countr.v pasture land with refer11ee t·o the.
For example, the phosphorus requirement for growth as a percentage of the fed ration is between 0·1 and 0·26 per cent. An examination of the relevant data in Tables 4 and 6 reveals that both cattle and sheep consume sufficient phosphorus throughout the year for maximum growth on the pastures in Area 1. 13, 14, 15 and 16 show that an intake below the optimum requirement for growing cattle and sheep occurs but rarely during the year.
Average monthly values fluctuate at a higher level and the annual averages for calcium in the case of the three areas are respectively and 0·40 percent. On the other hand, the pastures in Areas 6, 9, 10 and 11 are generally somewhat richer in potassium than any of the other areas from Ko. Sodmm and chlorine figures on the whole fluctuate in a most uneven manner but never fall to the low levels indicated for some of the grass lanrl 1neas.
15, 16, 17 and 18 of the desert: Bush and desert areas. Both sodium and chlorine levels are exceptionally high. 11.0 grams of sodium was apparently sufficient for the normal production of the same amount of milk per day. However, in the case of the Desert Succulent region, values are generally lower in winter than during the summer months.
In conjunction with the relatively small fluctuation of cn1dr fiber numbers during the year, for example 34· 6 per cer1t.
GENERAL SUMMARY AND CONCLUSIONS
This is fortunate, since most IJhosphatir supplements in practice. prt>cipitated calcium phosphate. Degel.meal with atinized bones, etc., would facilitate the intake of stock potassium, which is usually already much more than the phosphorus contained in the pasture eaten. It is considered, therefore, that the taking of pastures throughout the year and the variation of their calcium-phosphorus ratios from approximately normal,·:due to the change of periods of active growth to an unfavorable ratio,; during periods of food scarcity, such as drought and winter, in sunny areas, when phosphate supplements are usually given or occasional improvement in the ratio caused, what appears to be a periodically unfavorable ratio, is of no practical effect in animals. entirely dependent on pastures for their food supply. For the purposes of discussing the results obtained, the country as a whole has been divided into eighteen different areas and tables giving the average composition from month to month of pastures in each area built separately. the following is a brief summary of the results obtained.
Another distinguishing feature of the two field types is the difference in chemical composition between winter and summer pasture: while the former type shows only small fluctuations over the course of the year, the difference in the percentage content of certain constituents during winter and summer significantly. in the case of grass pastures. In meadows that mainly consist of silence, this COJ content varies between 0.11 and 0.20 percent. The value of crude protein in the grass meadows decreases from 7.0 to 9.0 percent. in winter, while in pastures composed mainly or entirely of shrubs, the percentage of this component varies during the year between 7 · 0 and 10 · 0.
However, differences in the percentage of these components are noticeable in the pastures of one region compared to those of another. During winter the former component varies between 0 · 29 and 0 · 63 percent. in the grassy meadows of the Cliffereut regions. The sodium average figures drop from a maximum of 0 08 percent. in some grass meadows, while in others these values vary between 0.10 and 0.25 percent. in the course of the year.
The average sodium and chlorine content is extremely high in some pastures, which consist mainly of shrubs. Based on the estimated growth requirements of cattle and sheep, all South African natural pastures consisting mainly or entirely of grasses are deficient in phosphorus, crude protein and in some areas sodium for five to nine months of the year, depending on the area. Furthermore, based on the average phosphorus value, these grass pastures do not contain enough of this nutrient at any time of the year to provide the need for the additional function (eg pregnancy or lactation) of the animals imposed on growth.
A cow that produces two liters of milk, however, may not consume enough of this component in the winter pastures of some grassland areas. This and other concomitant deficiencies in the diet will result in a generally lowered rate of metabolism, and this condition may again be responsible for the fact that the symptoms characteristic of a single mineral deficiency, such as phosphorus, do not manifest themselves to such an extent under practical farming conditions. measures that taking into account the average phosphorus content of our pastures, as shown in this report, in connection with the estimated requirement of animals for this ingredient, would be expected. In conclusion, it can be said that from a study of the data presented on these pages, it seems reasonable to conclude that the practice of feeding phosphorus supplements in certain areas is advocated by this.
ACKNOWLEDGMENT
