What do animals get from soil?

Press, Volume CXI, Issue 32666, 23 July 1971, Page 18

What do animals get from soil?

Sheep or cattle on close-grazed pastures eat a lot of soil along with their feed, and scientists of the Department of Scientific and Industrial Research and Massey University are trying to measure the effects this has on the animals’ nutrition.

Studies in recent years have shown that a sheep may eat 20 to 1001 b and a dairy cow 200 to 10001 b of soil a year. Such quantities suggested the possibility that the animals might be deriving part of their mineral requirements directly from soil rather than indirectly through pasture plants—specially in winter, when pasture is short and soil intake is highest. So the Soil Bureau and Applied Biochemistry Division of the D.S.I.R. and the dairy husbandry department of Massey University have undertaken collaborative experiments to find out just what animals get from ingested soils.

As a preliminary, Dr W. B. Healy, of the Soil Bureau, ran a laboratory experiment in which fluids from different parts of the ruminant digestive tract were shaken with soils. “Before-and-after” analyses showed that the fluids were capable of extracting quite large amounts of various elements from the soils. Different soils released different amounts of nutritionally important elements. A large number of New Zealand soils were screened in this way before feeding

trials were started. During the past year. Dr G. F. Wilson, of Massey, and Dr Healy conducted a trial in which newly weaned lambs were put on a semisynthetic diet consisting mainly of lucerne, meal and starch. Some of them were also given 50 grams of soil a dav, administered as a drench, and it was found that this increased the amount of selenium in their blood by as much as 50 per cent in six weeks. The soils used were Egmont brown loam from Taranaki, and Papakauri clay loam from Northland —and it was interesting that their relative ability to release selenium was much the same in the feeding trial as in the laboratory experiment. This trial, still in progress, is being followed up by Dr N. D. Grace, of the Applied Biochemistry Division, and Dr Healy in a further experiment with wethers on a more normal diet of cut and dried pasture plus 100 grams of soil daily. The soils in this case are Egmont brown loam and Waikiwi silt loam from Southland. The animals are boused indoors and are being fed at two levels—maintenance,

and 50 per cent above maintenance. Thus differences between the soils can be measured under two feeding regimes, the poorer of which is roughly equivalent to hard winter grazing. Changes in the mineral status of the sheep are being carefully studied to see what nutritive effects the soils have under these conditions. If the results look sufficiently promising, further studies will be undertaken using pregnant and lactating animals with a higher demand for nutrients.