Author:

Keywords:

okapi, glucosuria, fermentation

Abstract:

Preliminary data on metabolic profile of okapis with glucosuria Sarah Depauw1, An Cools2, Francis Vercammen3, Eline Praet2, Geert Janssens2 1Odisee College University, Sint-Niklaas, Belgium; 2Laboratory of Animal Nutrition, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; 3Centre for Research and Conservation, Royal Zoological Society of Antwerp, Antwerp, Belgium. Correspondence email: sarah.depauw@odisee.be Currently, it is recognized that glucosuria in captive okapis is a worldwide phenomenon. Urine sampling of okapis from the Epulu Okapi Reserve in the Democratic Republic of Congo excluded the presence of glucosuria in the wild, thereby indicating captive management factors to be the cause. Although there is a general belief that feeding mismanagement of this strict browser causes glucosuria, the phenomenon still remains unexplained. Moreover, a drastic decrease in sugar and starch content in the diet did not reduce glucosuria in 4 adult captive okapis. However, this diet still contained considerable amounts of highly fermentable fiber, in contrast to browse. Rumen acidosis and laminitis occur within the captive browsing ruminant population, which are both induced by gut fermentation imbalances caused by highly fermentable carbohydrates. We hypothesize that glucosuria in the captive okapi is also linked to imbalances in foregut fermentation processes. Frozen urine samples (10) from 4 glucosuric okapis of Antwerp Zoo were available, with samples from different life stages per animal. From 1 okapi, urine samples before the onset of glucosuria were also present. Samples were analyzed for glucose, free amino acid and acylcarnitine content. Acylcarnitines are a reflection of the corresponding acyl coenzyme A compounds, that indicate the way and extent nutrients are used for energy. Despite difference in life stage or severity of glucosuria, urinary glucose concentrations were positively correlated with metabolites derived from gut fermentation processes (acetylcarnitine (r=0.976; P<0.001), propionylcarnitine (r=0.848; P<0.001)). Although this might be a first indication for the link between glucosuria and fermentation, this requires further assessment, since these metabolites can, at least partly, also originate from other metabolic processes. Furthermore, the results suggest that the glucose metabolism is not the only problem in these animals, since multiple positive correlations were found between urinary glucose concentrations and free amino acids (e.g. valine, r=0.979= 0.96; P<0.001; leucine, r=0.978; P<0.001). The lack of creatinine measurements implies that certain correlations may only exist because of dilution effects. Therefore, also metabolite ratios were tested, since ratios are independent of dilution. Several metabolite ratios were also tightly correlated with glucose concentration: for instance propionylcarnitine:acetylcarnitine positively correlated with glucose (r=0.666; P=0.009) suggesting a shift to a higher ruminal propionate:acetate ratio. Captive okapis suffering from glucosuria thus show an altered metabolic profile in the urine that can help explain the phenomenon. The profile indicates that it is therefore still worthwhile exploring more browse-based diets for okapis in the prevention of glucosuria.