Enumeration of anaerobic oxalate-degrading bacteria in the ruminal contents of sheep

Abstract

Concentrations of oxalate‐degrading anaerobes in ruminal contents of sheep were determined from counts of colonies producing clear zones on a calcium oxalate medium (D agar with 7 mM CaCl2). Viable counts of oxalate degraders from a 55‐kg sheep fed a diet containing 32% halogeton (4.6% oxalate) averaged 2.6 × 106/ g (dry weight). When the halogeton concentration in the diet was reduced to 16%, counts of oxalate degraders decreased nearly 300‐fold. Oxalate‐degrading isolates from this sheep were similar to OxB, the type strain of Oxalobacter formigenes. When a 45‐kg sheep was fed diets containing 2.2, 1.5, and 0.8% oxalate, viable counts of oxalate degraders (enumerated on D agar with 14 mM CaCl2 and 20% filter‐sterilized ruminal fluid) represented 0.85, 0.52, and 0.06% of the total viable population, respectively; total viable counts were essentially unchanges by these concentrations of dietary oxalate. Similar percentages of oxalate degraders were also observed when a 23‐kg sheep was fed diets containing 1.5 or 0.8% oxalate. This report presents the first direct measurements of the concentrations of oxalate‐degrading bacteria in the rumen and supports the concept that the availability of oxalate in the diet influences the proportion of oxalate‐degrading bacteria in the rumen

The Rumen Microbial Ecosystem

“…Halogeton glomeratus is a plant that can contain oxalate amounting to more than 20% of the dry weight of the plant, and large death losses can be associated with sudden Halogeton exposure. This increased tolerance is due to increased concentrations of the oxalate-degrading anaerobe Oxalobacter formigenes Daniel et al, 1989). Fully adapted animals may tolerate a diet of 100% Halogeton (James and Butcher, 1972).…”

Biosynthetic pathways in Oxalobacter formigenes

“…When the dietary oxalate was below 3%, 0. formigenes could not be detected (Daniel et al 1987a). A similar effect was found between dietary oxalate levels and colonization in sheep (Daniel et al 1989). Other strains of O. formigenes isolated from monogastric animals also colonized laboratory rats fed the high oxalate diet.…”

“…Sheep can become adapted to dietary levels of halogeton that would intoxicate a naive animal (Allison and Reddy 1984;James 1972). Rumen microbial populations from adapted animals degrade oxalate faster than unadapted populations (Allison et al 1977;Daniel et al 1989), and this is probably what protects the animal from acute poisoning. However, increasing amounts of oxalate will eventually overwhelm the rumen microbes and the animal becomes intoxicated (Allison et al 1977).…”

Toxification and Detoxification of Plant Compounds by Ruminants: An Overview

“…It has been established that microbial adaptations provide detoxification of plant toxicants such as nitrate, nitrite, nitropropanoic acid, oxalate, prussic acid (and cyanogenic glycosides), sulfate and sulfide, some alkaloids (e.g., mimosine) and, perhaps, even some mycotoxins (James et al 1975(James et al , 1988Smith 1986;Seawright et al 1988;Daniel et al 1989;Allison et al 1989; see also other reports from this Symposium). It has been established that microbial adaptations provide detoxification of plant toxicants such as nitrate, nitrite, nitropropanoic acid, oxalate, prussic acid (and cyanogenic glycosides), sulfate and sulfide, some alkaloids (e.g., mimosine) and, perhaps, even some mycotoxins (James et al 1975(James et al , 1988Smith 1986;Seawright et al 1988;Daniel et al 1989;Allison et al 1989; see also other reports from this Symposium).…”