Abstract:
Animal Production in Australia ABSORPTION AND EXCRETION OF LACTIC ACID ISOMERS IN PIGS M.J. SISSONS*, P.D. CRANWELL* and A.W. BELL* Very high concentrations of D(-) and L(+) lactate (D and L) are regularly found in the stomach of sucking pigs reared under conventional conditions (Cranwell et al. 1976). In an experiment to determine the absorption and excretion of the two isomers, blood and urinary lactate concentrations were assayed following regular intragastric injection of milk plus lactate. Three Large White, sow-reared pigs aged 4 to 9 weeks were prepared with chronic jugular catheters and gastric fistulae. Each animal received at random each of the following treatments at 5 to 10 d intervals: hourly intragastric of either cow's milk (control), or 250 mM racemic injections of 15 ml/kg o*75/h lactic acid in cow's milk for 19 h. Blood was sampled at intervals and all urine collected for 28 h from the commencement of the experiment. Plasma and urine were assayed for L (Lundholm et al. 1963) and D (Brandt et ai?. 1980). Mean (+- SEM) plasma D and L concentrations during control injections were D, 0.173 _+ 0.007 mM and L, 1.416 ,+ 0.063 mM. Plasma D increased and reached a plateau (4.6 fold above baseline) 250 min after the first injection and decreased to baseline levels 225 min after the last injection (Fig. 1). Plasma L showed no definite pattern but was nearly always above control levels. Urinary excretion of total lactate, L and D as a percent of the total amount given were 4-7%, 2-3% and 7-14% respectively. I I I I IIIIIIIIIIIIIIII Fig. 1 Mean plasma D (0) and L (A) concentrations following intragastric injections of racemic lactic acid in cow's milk. I - denotes time of intragastric injections In conclusion, the observations that D reaches a stable and elevated concentration following repeated intragastric injection of lactate and only a small proportion is excreted in the urine suggest that D is rapidly metabolized and/or its absorption is limited. BRANDT, R.B., SIEGEL, S.A., WATERS, M.G. and BLOCH, M.H. (1980). Anal. Biochem. 1020 - - 39. CRANWELL, P-D., NOAKES, D.E. and HILL, K.J. (1976). Br. J. Nutr. 35: 27~. LUNDHOLM, L., MOHME-LUNDHOLM, E. and VAMOS, N. (1963). Acta PhysiolScand. 58: 243. Z * School of Agriculture, La Trobe University, Bundoora, Vic. 3083. 673
