Quantitative analysis of acid-base balance in Bos indicus steers subjected to transportation of long duration.

There is a lack of information pertaining to the effects of transport stress on the acid-base physiology of ruminants. The effect of transportation and/or feed and water deprivation on acid-base balance was studied using 19 2-yr-old Bos indicus steers. The steers were allocated to one of three groups: 1) control, offered ad libitum access to feed and water (n = 8); 2) water and feed deprived, offered no feed or water for 60 h (n = 6); and 3) transported, offered no feed or water for 12 h, and then transported for 48 h (n = 5). Blood gases, electrolytes, lactate, total protein, albumin, anion gap, strong ion difference, and total weak acids were determined at the conclusion of transportation. Arterial blood pH did not differ among the experimental groups. Partial pressure of carbon dioxide (pCO2) was lower for the water and feed deprived (P = 0.023) group than for the control group. Plasma total protein, albumin and total weak acid concentrations were higher for the transported (P = 0.001, P = 0.03, P = 0.01) and water- and feed-deprived (P = 0.000, P = 0.003, P = 0.001) groups, respectively, compared with the control group. Transported animals had a lower plasma concentration of potassium (P = 0.026) compared with the control animals. This study demonstrates that although blood pH remains within normal values in transported and fasted steers, the primary challenge to a transported or feed- and water-deprived animal is a mild metabolic acidosis induced by elevated plasma proteins, which may be the result of a loss of body water. The loss of electrolytes had little effect on the acid-base balance of the animals.