What is the recommended fluid and antimicrobial protocol for calf scours based on dehydration grade?

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Fluid therapy for calf scours is stratified by dehydration severity, with oral electrolyte solution (OES) for mild-to-moderate cases and intravenous (IV) fluids reserved for severe dehydration. Mild-to-moderate dehydration is managed with OES. Oral rehydration is of particular value because it permits treatment at the initial signs of scours, which reduces the severity of the condition in many cases.2 Re-Sorb (glucose, glycine, and electrolytes for oral solution) is one commercially available OES with an osmolarity of approximately 315 mOsm/kg and a pH of approximately 4.3.2 Key components of an effective OES are osmolality, sodium concentration, alkalinizing agent content (effective strong ion difference), and energy content — all of which influence abomasal emptying rate and the rate of sodium delivery to the small intestine.3 Severe dehydration — defined as a calf that is recumbent, comatose, or in shock — requires IV fluid therapy; OES is contraindicated in this state because oral therapy is too slow.2 Four crystalloid solutions are recommended for IV use in dehydrated calves: lactated Ringer's solution and acetated Ringer's solution for dehydrated calves without severe acidosis; isotonic (1.3%) or hypertonic (5.0% or 8.4%) sodium bicarbonate for calves with diarrhea and severe metabolic acidosis with hyponatremia; and hypertonic NaCl (7.2%) followed by an OES or water load for rapid resuscitation.3 Of note, 0.9% NaCl, Ringer's solution, and 5% dextrose are equally acidifying, while lactated Ringer's and acetated Ringer's are neutral to mildly acidifying — neither is optimized for neonatal calves.3 Hydration status is best estimated by measuring the magnitude of eye recession, duration of skin tenting in the lateral neck region, and urine specific gravity by refractometry.3 Antimicrobial therapy is indicated for bacterial scours (E. coli, Salmonella) and systemic illness, but OES products such as Re-Sorb contain no antibacterial agents.2 Antimicrobial and other