At previous NAEG meetings there frequently have been questions and discussions about the amount of soil a cow ingests during the grazing processes. of soil ingestion have been as high as 2 kg per day. Estimates A simple study was devised to provide an indication of the amount of soil ingested. After the rumens of two fistulated steers were completely emptied of all ingesta, the rumen and reticulum were rinsed with water and the wash water This cleansing process was bailed out to remove any residual sediments. The animals were allowed to graze for 24 hrs on the repeated three times. selected range. Areas grazed included the well-grazed inner compound of Area 13 and an ungrazed range near White Rock Spring. Following the grazing period, the ingesta was removed and agitated with water. The ingesta was washed through a screen (1.2- X 1.6-mm mesh) and the wash water saved. The rumen and reticulum were flushed with water three times and this wash water added to the ingesta wash water. The supernatant liquid was poured off and the sediments collected and heated at 450 procedure oxidized any residual bits of vegetation. weighed. C for 3 hr. This The residues were then The same procedures were followed in the examination of tinal tract from a cow sacrificed on January 28, 1976. the outer compound of Area 13 for her entire life. The fistulated steers and the sacrificed cow are summarized the entire gastrointesThis cow had grazed findings from both the in Table 3. It must be recognized that the sediment weights are approximate in that only those soil particles heavier than water were collected and undoubtedly some particles were entrapped in the villi or vegetation and were not released during the washing processes. Moreover, the data apply only to the individual animals on the day collected. However, the data from the permanent resident of the area (cow number 10) are considered to be significant as there would be no reason to believe that her grazing patterns would change significantly from day to day. These data suggest that the total amount of soil ingested is much less than 2 kg per day, and that a reasonable estimate would be between 0.25 to 0.5 kg. This is still a significant amount, as some of the sand particles ingested could remain in the gastrointestinal tract for long periods of time. If such particles should contain relatively insoluble transuranic elements, this period would provide more time for reactions involved in gastrointestinal absorption, so uptake could be greater than would be derived from conventional studies carried out in ruminant digestion investigations. When the fistulated steer data are examined, it is obvious that more soil is ingested from a heavily grazed area than from an ungrazed area. Also, the amount of soil increased with the amount of vegetation ingested. Neither of these observations is surprising. That more sediment is found in the rumens and reticula of the fistulated steers probably results from overeager grazing to fill the empty rumens. That is, they start out empty while the resident cow's rumen always contains some ingesta from the day before. 147