RESUMO
Oral electrolyte solutions (OES) are a common, on-farm therapy to reestablish hydration and electrolyte balances in scouring and stressed calves. The objectives were to determine the effects of OES alkalinizing agent and the presence of a milk replacer feeding before OES administration on the abomasal environment in healthy Holstein calves. Abomasum cannulation was performed on 16 Holstein bull calves at 5 d of age. One calf was removed from the study before the calves were randomly assigned to treatments at 9 d of age. Treatments were arranged as a 2-by-2 factorial, with the following factors: oral electrolyte alkalinizing agent [acetate (A) or bicarbonate (B)] and liquid meal type milk replacer (MR) + OES (MR-A, MR-B), or OES only (OES-A, OES-B)]. The OES differed only by alkalinizing agent. On d 9, calves assigned to MR-A (n = 4) or MR-B (n = 4) received their morning MR aliquot 0.5 h before feeding 2 L of OES; the OES-A (n = 3) and OES-B (n = 4) treatment groups were fed 2 L of OES only. Peripheral blood samples and postprandial abomasal fluid samples were collected to assess abomasal pH, abomasal emptying rate (AER), and ex vivo abomasal Escherichia coli growth potential. Postprandial pH was greater in calves fed MR or B-based OES. Abomasal emptying rate was slower in calves receiving MR + OES, regardless of the alkalinizing agent. Ex vivo E. coli colony-forming unit counts were greater in calves fed either MR + OES or bicarbonate-based OES. Supplementing bicarbonate OES in addition to MR alters abomasal dynamics and may promote E. coli growth in postprandial abomasal fluid, partially due to sustained elevations in gastric pH and delayed gastric emptying rates. The OES containing sodium acetate limited ex vivo E. coli growth potential in abomasal fluid, thereby potentially reducing the risk of additional enteric bacterial complications associated with OES therapy.