The Cause and Prevention of Lamziekte. 241 



It may well be, and to a certain extent must be, tbat the percentage 

 of phosphorus in a grass has to be correlated with its general feeding 

 value, and with the season of the year, in getting at a full explana- 

 tion of pica; that a mere analysis of vegetation for phosphorus 

 content is but a poor indication of the extent to which it is likely to 

 produce osteophagia ; and that neither the percentage amount nor 

 the absolute daily intake of phosphorus can be considered alone, but 

 that the proportion required is partly conditioned by the total amount 

 of food metabolized. There are several experimental indications 

 pointing in this direction which have to be worked up in the future, 

 imt for the moment we may content ourselves with a generalized 

 phosphorus theory. 



In passing, it may be mentioned that youngr crass growing over 

 burned veld, and subsequently subjected to drought, appeared to 

 produce more marked craving in grazing cattle than did neighbour- 

 ing unburnt veld. 



In regard to the chemical composition of the soil it mav at once 

 be stated that, other things being equal, a soil very low in phosphoric 

 oxide Avill tend to produce a veg-etation low in phosphorus content, 

 but that a limit is set by the minimum physiological reouirements for 

 growth of the plants concerned. The available phosphorus content 

 of a soil is reflected even more in the density of the vegetation it can 

 carry than in the phosphorus content of that vegetation, and a small 

 increase in the available phosphate of a soil (as by manurins") is more 

 likely to reflect itself in an increased luxuriance of srrowth. Other 

 factors also enter, and climate — especially rainfall— is important. 



Although, then, low phosphate content is characteristic of the 

 soils of lamziekte areas (a fact emphasized by .Turitz twenty years 

 ngo). a mere analysis of a particular soil is not sufficient to enable 

 one to estimate the degree of pica which will characterize the area 

 from which the soil is sampled. Two soils in different districts mav 

 show a similar nnnlvsis but yet differ in resrard to the incidence of 

 pica in the cattle thev support, and. a«5 alreadv shown, the degree of 

 pica •''5 dependput ur»on the season of the vear. 



The question of soil composition in relation to pica does, however, 

 deserve more attention than it has hitherto received, especially since 

 the soil from different parts of the same lamziekte farm may vary 

 considernblv both in composition and in depth. This is the case at 

 Armoedsvlakte. 



Certain manurial experiments are also in progress at Armoeds- 

 vlakte, but these are directed bv theoretical rather than immediately 

 practical considerations, since it is felt that any attempt to alleviate 

 pica bv phosphatic dressings would be far too costly over the wide 

 lamziekte areas of cheap land. Tlieoreticallv it miffht be possible to 

 break the etioloo-ical chain at this link, but so long as the farming f 

 the areas remains extensive rather than intensive the job would cost 

 more than the market value of the land. It may be casually 

 remarked in passing that any bone meal fed to cattle is not wasted 

 wholly in guardinsr against mortality from lamziekte, but o>oes to 

 enrich the soil and increase the burden of vegetation it can carry: a 

 very minor consideration, however, in view of the size of the areas 

 in question and the low price of the land. The effect of bone meal 

 on the condition of the animals — already mentioned as enhancing 

 their market value — is a more remunerative consideration. 



