Grain Engorgement Toxemia

History. In mid-January a cattle feeder has asked you to examine a feedlot full of 400-kg steers. The steers have been on free-choice grain from a self-feeder for several weeks. Three days ago a blizzard prevented the caretaker from deliver­ing feed to the feeders, and they were empty for 36 hours.

Clinical and Laboratory Examination. Two steers are isolated for physical examination; they are lethargic and must be coaxed to move. Their heart rates are all above IOO beats/min (normal, VFA rapidly, causing the rumen pH to diminish. As the rumen pH becomes lower, conditions become unfavorable for the growth and survival of CelluloseTermenting organisms and favorable for the growth of lactic acid-producing bacteria. This leads to the accumu­lation of lactic acid, a stronger acid than the VFAs. Thus, rumen pH becomes even lower, killing many of the normal microflora. Some of the lactic acid is absorbed, leading to a reduced blood pH and a life-threatening situation. Moreover, the large ruminal concentration of lactic acid and VFA results in a high osmotic pressure, drawing water out of the vascular fluid compartment and into the rumen. This leads to systemic hypovolemia, which may proceed to hypovolemic shock.

Treatment. This is a life-threatening situation, and the farmer will likely lose additional steers. Treatment is aimed at expanding the intravascular fluid volume, correcting the sys­temic acidosis, and reestablishing a normal rumen environ­ment. Severely affected steers should be evaluated to determine whether their prognosis is good enough to warrant the expense of therapy; if not, euthanasia should be employed. Initial treat­ment should consist of rapid intravenous administration of large quantities of alkalizing fluid. After the correction of fluid and acid-base disturbances, ideally the rumen should be emptied, cither by intubation with a large-bore stomach tube or by rumenotomy. In some cases, oral administration of an antifermentation agent, such as oil of turpentine, mineral oil, or an antibiotic, along with an alkalizing agent, is an accept­able alternative to emptying the rumen. After the rumen environment is brought back to normal, it may be helpful to re-inoculate the rumen with material taken from the rumen of a normal animal.