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Metabolism of Glycolic Acid in Lactating and Nonlactating Goats and in a Calf^1,2,

Department of Animal Science, Iowa State University, Ames 50010

ABSTRACT

Several characteristics of glycolic acid metabolism were measured in lactating and nonlactating goats by a primer dose plus 3-hour constant infusion technique. The average turnover rate of glycolic acid was 1.7 g per hour, and no lactation effect was observed. The turnover time averaged 9.5 minutes with a half-life of 6.6 minutes. Administered ¹⁴C-glycolic acid was rapidly oxidized to ¹⁴CO₂ with 44% appearing in CO₂ by 5 hours. About 1% of total expired CO₂ was derived from glycolic acid.

Some glycolic acid was incorporated into milk components. After 5 hours, .41% of the infused ¹⁴C-glycolic acid was incorporated into casein, .08% into fat, and about 2% into lactose. During an identical period, ¹⁴C-glucose was incorporated into casein, fat and lactose at .4%, .5% and 32% of the administered dose. Glycolic acid was detected also in rabbit, swine, and horse blood.

Turnover rates of glycolic acid in a calf were similar to those in the goats, and after phlorizin treatment about the same amount of radioactivity was in urine glucose as was in milk lactose from the lactating goats. The rate of oxidation to CO₂ was somewhat slower. Only a trace of radioactive glycolic acid was excreted in the urine.

¹ Journal Paper J-6862 of the Iowa Agriculture and Home Economics Experiment Station. Ames, Iowa. Project 1671. Supported in part by funds provided by Grant AM-10706, Department of Health, Education and Welfare.

² The data from the goat experiments were taken from a thesis presented by the senior author to the Graduate College of Iowa State University as partial fulfillment of the requirements for the Master of Science degree.

³ Present address: Department of Dairy Science, Michigan State University, East Lansing, Michigan 48823.