Effect of milk and oral electrolyte solutions with and without bicarbonate on abomasal luminal pH and systemic acid-base status in calves.

摘要

Reports concerning the effect of feeding calves electrolyte solutions with or without bicarbonate on abomasal luminal pH differ. However, it is known that feeding HCO3- ions results in an increase in abomasal pH. This should have negative effects on abomasal digestion and non-specific resistance to infection, which both require acidic pH values. A plastic cannula was surgically inserted into the abomasum of eight healthy calves. Subsequently, the calves were fed with either: (1) cow milk; (2) electrolyte solution without bicarbonate mixed in milk or (3) electrolyte solutions with bicarbonate mixed in water for seven to nine days, respectively. In addition, a mixture of equal parts of milk and electrolyte solution with bicarbonate was administered. Samples of abomasal content were obtained before feeding and monitored every 15 minutes for four hours. pH, the area under the pH curve (AUC) and the strong ion difference (SID) were determined. In addition, the systemic acid-base status of arterial and venous blood was determined using Henderson-Hasselbalch equation and Stewart variables. Results showed that milk feeding increased the abomasal luminal preprandial pH from a basal value of 2.00+or-0.44 to a peak value of 4.70+or-0.41, 30 min after feeding and a subsequent decrease to 2.43+or-0.37 (4 h postprandial), resulting in an AUC of 898+or-87 (100%). Abomasal pH was increased significantly to 5.35+or-0.31 and decreased to 2.95+or-0.78 (AUC=1086+or-89) after suckling the milk with the electrolyte solution without bicarbonate. When electrolyte solution containing bicarbonate was mixed with water, pH values reached the peak value of 6.59+or-0.28 (AUC=1119+or-45 or 125%). The mixture with milk induced an increase in abomasal luminal pH to 6.22+or-0.12 and AUC of 1126+or-44 (125%). AUC values in the bicarbonate groups were significantly higher than in the milk-fed group. After all the feedings, an alkaline reaction was observed in the arterial and venous blood samples, which was significantly higher in the group fed electrolyte solution containing bicarbonate (mixed with water). While pCO2 remained constant, pH, [HCO3-], [BE], [SID3] increased and [Atot] decreased. The study showed that feeding electrolyte solutions without bicarbonate significantly increases abomasal luminal pH. While addition of bicarbonate results in transient postprandial elevation of abomasal luminal pH..