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Fermentation, Absorption and Feeding Results with L(+) Lactic Acid Monomer and Polymer and DL-Lactate Salts¹

Michigan State University, East Lansing

Abstract

Three groups of six heifers ranging from 127 kg. to 218 kg. body weight were fed salt, dicalcium phosphate, corn silage, hay and 0.9 kg. of soybean meal daily. Silage and hay dry matter comprised equal portions of the ration. Additionally, Group 1 received 227 gm./day of DL-lactic acid as the sodium-calcium salt; Group 2, 227 gm./day of L(+) lactic acid as 50% aqueous solution; and Group 3, 227 gm./day of corn. Average daily gains for Groups 1, 2 and 3 were 0.72, 0.69 and 0.72 kg. for the 84-day trial. Differences among groups for feed intake were not significant.

Three groups of four lactating cows were assigned to similar rations during a reversal trial with three periods of 28 days. Daily milk production averaged 19.6, 18.9 and 19.2 kg. for the three groups, respectively. Milk produced by the control group did not differ significantly from that produced by the lactate groups, but the difference between the two lactate-supplemented groups approached significance (P<.09). The differences among groups were small and nonsignificant with respect to milk composition, hematocrit, blood glucose, blood lactate and blood fat. Lactate feeding tended to elevate rumen lactate, rumen propionate or butyrate and urine lactate concentrations.

Rumen contents from three cows were incubated for 2 hr. with buffer and either L(+) lactic acid or 43% polymerized L(+) lactic acid to yield a final concentration of 0, 50, 75 or 100 mg./100 ml. Monomer destruction increased with concentration equaling 593 µg./ ml. per hour at 100 mg./100 ml. Destruction of 43% polymer at this same concentration was only 167 µg./ml. per hour. Administration of polymerized lactic acid increased the polymer content of blood, but it had no significant effect on gain or feed efficiency.

¹ Journal Article No. 3410 from the Michigan Agricultural Experiment Station.