Recovery of intravenously infused chromium EDTA and lithium sulphate in the urine of cattle and their use as markers to measure urine volume

Abstract

A series of metabolism experiments investigated the recovery of continuous-, intravenously infused chromium complexed with ethylenediamine tetra-acetic acid (CrEDTA) and lithium sulphate in the urine of cattle with a view to using the markers to estimate urine and metabolite output in grazing cattle. The recovery of Cr in urine from these infusions was similar (90%) in metabolism trials when cattle consumed three very contrasting diets: high-grain formulated pellet, lucerne hay (Medicago sativa) or low-quality native grass hay (predominantly Heteropogon contortus). By contrast, Li recovery in urine averaged 46.3 6 0.40% and 72.6 6 0.43% for native pasture and lucerne hays, respectively, but was not constant across days. There was negligible transfer of Cr from CrEDTA in blood serum to the rumen or faeces, whereas appreciable quantities of infused Li were found in both. The ratio of urine volume estimated by spot samples and marker dilution of Cr, to urine volume measured gravimetrically, was 1.05. In grazing studies using rumen-fistulated (RF) steers grazing seven different tropical and temperate grass and legume pastures, the ratio of concentrations of purine derivatives (PD) to Cr in spot samples of urine was shown to vary diurnally in the range of 49% to 157% of the average 24 h value. This finding indicated the need for regular sampling of urine to achieve an accurate average value for the PD : Cr ratio in urine for use in estimating urinary PD excretion and hence microbial protein production in the rumen. It was concluded that continuous, intravenous infusion of CrEDTA resulted in a constant recovery of Cr in the urine of cattle across diets and, provided an intensive sampling regime was followed to account for diurnal variation, it would be suitable as a marker to estimate urine volume and urinary output of PD in grazing cattle.

Efficiency of rumen microbial protein synthesis in cattle grazing tropical pastures as estimated by a novel technique

“…The work reported here represents the first known attempt to estimate EMPS in cattle grazing tropical pastures typical of those used in the northern Australian beef industry, and utilised novel methodology including intra-jugular infusion of CrEDTA in cattle to determine urine output. This method (Bowen et al 2009) proved sufficiently robust to estimate MCP production under field conditions, when used in association with measurement of PD concentration in spot samples of the urine. These approaches avoid the errors associated with using creatinine as an internal marker, given the variability in its excretion among individuals and with diet type (Faichney et al 1995), and do not require post-ruminal fistulation of the animal and associated complicated procedures for determining digesta flow and for separation of microbes.…”

“…Thus, calculations of faecal output and intake using the n-alkane marker technique were performed using the dosed C 36 n-alkane only. Total PD excretion (sum of allantoin, uric acid, hypoxanthine and xanthine) in urine was calculated from PD concentrations in spot urine samples using the measured Cr infusion rates for each animal on each day and adjusting for 0.90 urinary recovery, as determined by Bowen et al (2009). The flow of MCP to the intestines of steers was calculated using the equations proposed by Chen and Gomes (1995).…”

“…Traditional methods required the use of postruminally cannulated animals, the employment of prolonged, steady, intraruminal infusion of markers and procedures for measuring digesta flow and for separation of microbes from digesta (Beever et al 1986;Cruickshank et al 1992). Bowen et al (2009) proposed a new method of estimating MCP production in grazing cattle. It involved continuous intravenous jugular infusion of chromium (Cr)-EDTA and measurement of both Cr and purine derivative (PD) concentrations in spot urine samples to estimate urine output and, thereby, total PD excretion.…”

“…The tropical pasture types studied were representative of those grazed by cattle in northern Australia. Some aspects of the research have appeared elsewhere (Bowen et al 2001(Bowen et al , 2003(Bowen et al , 2008a(Bowen et al , 2008b(Bowen et al , 2009(Bowen et al , 2010a(Bowen et al , 2010b.…”