The aim of this study was to evaluate the effects of two dietary supplements (monensin and a live yeast culture) on acid-base balance in steers maintained in a commercial feedlot system, considering effects over the finishing productive cycle. Steers (no. =42) were allotted randomly to one of the three study groups: (1) control group (no supplementation, C), (2) monensin supplementation (MON), and (3) live Saccharomyces cerevisiae strain 47 supplementation (SACC). Venous blood samples were collected for the measurement of acid-base parameters and l-lactate. Production parameters were also used as a complementary tool for understanding the internal changes associated with supplementation. During the finishing period, MON steers tended to gain more efficiently than C and SACC steers. In the C group, the finishing-period diet caused a progressive decline in blood bases, in line with the high-grain diet consumption. In contrast, supplemented animals did not show this trend, although lower HCO3− and base excess values were registered in SACC steers than in MON, indicating that ionophore supplementation is less effective for reducing blood base consumption than yeast supplementation. In our study, the lack of the expected response to yeast supplementation may be attributable to the high crude protein content of the ration, a common feature of commercial feedlot industries.

We have studied the acid-base equilibrium in 12 patients with end-stage renal failure (ESRF) during capnoretroperitoneoscopic nephrectomy. Bupivacaine (12 mL, 0.375%) and morphine (2 mg) were given in the lumbar epidural space, and fentanyl (0.5 μg kg−1) and midazolam (50 μg kg−1) were given intravenously. Anaesthesia was induced by thiopental, maintained with halothane carried by oxygen enriched air (inspired oxygen fraction = 0.35), and ventilation was achieved with a tidal volume of 10 mL kg−1 at a rate of 12 min−1. This procedure resulted in a mild degree of respiratory acidosis that was cleared within 60 min. We conclude that capnoretroperitoneoscopic nephrectomy can be performed in patients with end-stage renal failure with minimal transient respiratory acidosis that can be avoided by increased ventilation.

A well fermented grass silage was mixed with 9·3 g lactic acid per kg silage supplied either as the free acid (lactic acid) or partially neutralized to pH 5·2 with sodium hydroxide (sodium lactate) to give three dietary treatments. Treatment with lactic acid reduced silage pH (P < 0·05) from 4·03 to 3·80 and increased (P < 0·01) the amount of sodium hydroxide required to raise silage pH to 6·5 (neutralizing value) from 167 to 261 mmol/kg silage and osmolality (P < 0·01) from 712 to 854 mosmoljkg silage; sodium lactate treatment increased (P < 0·05) silage pH to 4·15 and osmolality (P < 0·01) to 964 mosmoljkg silage but did not change neutralizing value.

Wlien fed in a randomized-block design to either six intact lambs or to four rumen fistulated sheep lactic acid treatment reduced (P < 0·05) silage dry matter (DM) intake (g/kg weight0·75) from 34·7 to 27·8 for intact sheep and from 35·5 to 29·9 for fistulated sheep. Intakes of the sodium lactate-treated silage tended to be higher (39·2, intact and 40·1, fistulated sheep, g/kg weight0·75) than the control silage. Silage DM intake was correlated more closely with neutralizing value (r2 = 0·34) than pH (rz = 0·24).

Treatment of silage with lactic acid or sodium lactate did not change rumen pH, volatile fatty acid patterns or osmolality. Blood pH, pCO2 and bicarbonate concentrations were not changed by the diets offered and were within normal ranges. Urine acid-base balance was not affected by lactic acid treatment whereas urine pH, and bicarbonate and sodium excretion were (P < 0·01) increased by sodium lactate treatment of the silage.