TRACE ELEMENTS IN ANIMALS 135 



Ferguson, Lewis and Watson found that the scouring of 

 cattle and sheep resulting from the absorption of molybdenum 

 can be prevented and cured by dosing the animals with copper 

 sulphate. On very teart land a daily dose of 2 g. of this salt for 

 cows and 1 g. for young stock was found to be adequate for the 

 purpose, while on mildly teart land a smaller dose would probably 

 be sufficient. The mode of action of the copper is not evident. 



Experimenting with six dairy cows, Ferguson (1943) found 

 that giving a daily dose of 2 g. of copper sulphate to each cow 

 for from 10 to 18 weeks produced no ill effects, the cows re- 

 maining in perfect health and calving normally. Having regard 

 to the facts that ( 1 ) on most farms in teart areas there is a pro- 

 portion of non- teart land, so that cattle would graze on the 

 teart land for only a portion of their time, and (2) the scouring 

 tendency of the herbage varies with the season, being greatest 

 in early spring and September and less at other times, Ferguson 

 considers that continuous daily dosing with copper sulphate 

 would probably not be necessary for more than about 6 weeks, 

 so that the cows used in the experiment actually received con- 

 siderably more copper sulphate than would usually be necessary 

 to prevent scouring. 



Ways to reduce the teartness of pastures were also examined 

 by Lewis. He found that application of acidic nitrogenous 

 fertilizers containing ammonium sulphate reduced the propor- 

 tion of molybdenum in the herbage. This was largely due to a 

 reduction in the proportion of clover in the herbage, but the 

 actual proportion of molybdenum in the grasses was also reduced. 

 This might have been due to the ammonium sulphate bringing 

 about an increase in the yield of the grasses without increasing 

 the weight of molybdenum taken up. Also it has been noted that 

 teart soils are neutral or alkaline. Rendering the soil more 

 acidic will reduce the availability of the molybdenum and so 

 induce a lowering in molybdenum absorption by the plants. 



Another point observed by Lewis was that the molybdenum 

 content of newly sown grasses is low, but increases with age, 

 although clovers have a high molybdenum content from the 

 beginning. A system of ley farming with short leys and with only 

 a small percentage of clover would thus appear to be very 

 suitable for teart land. 



