Rothamsted Symposium on Trace Elements 138 



glycinate were shown to cause a rather irregular variation of the 

 copper content of the blood serum. The copper content of the 

 liver of normal, adult horses shows considerably less variation 

 than the copper in cattle liver, the limits observed being 13 and 

 32 mg per kg (dry matter basis). 



A relationship between the intake of manganese and the oc- 

 currence of grass tetany in cattle in the Netherlands could not be 

 established. 



A general survey of the manganese content of 645 samples of 

 pasture grass and hay originating from various soils results in sev- 

 eral conclusions. Significant differences were shown to exist be- 

 tween the manganese values of pasture grass originating from 

 sandy, peaty and clayish soils, the average values being 19.1, 15.2, 

 and 11.4 mg per 100 g, dry matter basis. Presumably the pH 

 value of the soil is of most importance as really alkaline soils show 

 the lowest manganese content in pastures. 



No significant difference was observed between the manga- 

 nese values in hay originating from sandy and peaty soil, respec- 

 tively. A significant difference was, on the other hand, shown 

 to exist between these two kinds of hay and hay originating from 



clay. 



The occurrence of sterility in catde, as a result of manganese 

 deficiency, should not be excluded. This kind of sterility may be 

 expected to occur in clay areas with an alkaline reaction of the 

 soil. 



Summary 



1) Real and conditioned deficiency of copper in cattle has been 

 observed in the diluvial and alluvial parts of the Nedierlands. 

 So far a shortage of cobalt in catde has been mainly observed in 

 diluvial areas. 



2) Pasture grass originating from sandy soils has more manga- 

 nese than pasture grass from peat soils. Pasture grass from clay 

 has the lowest manganese content. The manganese content of 

 hay from clay is clearly lower than of hay originating from sand 

 and peat. The pH value of soils plays an important part in the 

 absorption of manganese by plants, the lower the pH, the more 

 manganese is absorbed. Manuring of pastures on clay lands with 

 Thomas phosphate, containing much manganese, results in a con- 

 siderable rise of the manganese content of the pasture grass. Ster- 



