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Changes in Metabolism of Biuret during Adjustment to a Biuret-Supplemented Diet^{1, 2,}

University of Illinois, Urbana⁴

Abstract

Experiments were conducted to study the adaptation response of sheep to dietary biuret. Measurements of nitrogen retention and direct determination of biuret in urine over a period of 51 days indicated that a significant part of the increase in nitrogen retention could be accounted for by a corresponding decrease in the amount of biuret in urine.

An abrupt change in source of nitrogen, accomplished by substitution of biuret for urea in the diet of sheep which had been accustomed to urea for 1 mo. or more, resulted in sharp initial decreases in nitrogen retention. Approximately 50% of the dietary biuret was excreted in urine as biuret during the 11- to 17-day period and decreased to about 30% after 45 days. Measurements of metabolism of biuret^–14C in vitro were made by counting the evolved ¹⁴CO₂. Substitution of biuret in the diet for urea resulted in decreased recovery of ¹⁴C as ¹⁴CO₂ for the first 9 days following the change. After 17 days, recovery of ¹⁴C was higher for biuret-supplemented lambs than for urea-supplemented lambs. There did not appear to be a significant difference in ¹⁴C recovery for lambs fed biuret or urea after 51 days. Metabolism of biuret^–14C in vitro for urea-supplemented lambs did not change appreciably over 51 days.

Results obtained add support to the hypothesis that the adaptation in biuret utilization is due to changes in the ability of microorganisms to metabolize biuret. In these studies a significant part of the early adaptation in biuret utilization appeared to be attributable to recovery from a decreased metabolism of biuret observed in vitro during the first 9 days following addition of biuret to the diet.

¹ Data taken from thesis submitted by the senior author to the Graduate College, University of Illinois, in partial fulfillment of the requirements for the Ph.D. degree.

² Supported in part by federal funds (Hatch 20–336) and by grant-in-aid from Dow Chemical Company, Midland, Michigan.

³ Present address: Animal Science Department, University of Idaho, Moscow.

⁴ Animal Science Department.