The use of esophageal-fistulated steers to determine flourine intake of cattle grazing flourine-contaminated forage

During the grazing seasons of three consecutive years, esophageal-fistulated steers were used to determine fluorine intake of cattle grazing fluorine-contaminated pastures. Forage samples obtained by the fistulated steers were adjusted for losses of fluorine due to saliva leaching. The adjusted fluorine content of this forage (selected forage) was compared with that of samples of available forage. The effects of season, soil fluorine level, plant height, steer and year on the fluorine content of selected forage were studied.

Significant differences between the available forage and the selected forage was observed. These differences indicated that esophageal-fistulated animals more accurately determined the total fluorine intake of grazing animals than did samples of the available forage.

Variations due to steer and year were not found to significantly (P > .05) affect fluorine level of selected forage. Season exerted a very highly significant effect (P 7lt; .001) on the fluorine content of selected forage. Forage grown in the winter and spring seasons had considerably higher fluorine content than forages grown in the summer and autumn. Soil fluorine level had a very highly significant effect (P < .001) on the fluorine content of selected forage. Fluorine content of forage increased approximately 3 ppm for each 100 ppm increase in soil fluorine. Plant height exerted a highly significant (P < .01) effect on the fluorine content of the forage. Within the range of plant heights studied (0.75 to 6.0 inches), fluorine content of the forage decreased about 19 ppm for each one-inch increase in plant height.