Endogenous excretion and true absorption of cobalt as affected by the oral supply of cobalt

Abstract

At the end of a 49-d experiment with 32 growing male rats, a period of 8 d was used to determine endogenous excretion and true absorption as well as apparent absorption and retention of cobalt with the aid of the isotope dilution technique. For this purpose, a single im dose of 58Co was applied at d 35 of the experiment. After that, urine and feces were collected separately from d 8 to 15 after injection of the isotope. The specific cobalt activity of the liver was used as an endogenous reference source. The basal diet provided 5.9 ppb cobalt, the different treatment groups were obtained by supplementing the diet with 0, 10, 50, 250, or 1250 ppb cobalt. The different diets were offered from the beginning of the experiment. In the balance period, apparent and true absorption as well as fecal excretion behaved similar to cobalt intake, whereas urinary excretion increased more rapidly with increasing cobalt supply. Endogenous fecal excretion accounted for 3.5 ng Co/d in the groups fed the diets without and with 10 ppb cobalt. An increase was not observed until supplementing the diet with 50 ppb cobalt. This increase between 250 and 1250 ppb cobalt was higher than the corresponding increase in the dietary cobalt supply. This indicates that endogenous fecal excretion might be more important for homeostatic regulation at a higher dietary cobalt concentration. Endogenous renal excretion as calculated from the results of the isotope dilution technique showed a similar kind of response to increasing cobalt supply as endogenous fecal loss. Nevertheless, the elimination of excessive cobalt mainly took place by adjusting urinary excretion, whereas the variations in true absorption and endogenous fecal excretion had no quantitative importance. Apparent and true absorption were on average 28.0 and 29.8%, respectively, of the cobalt intake. In the case of retention, a marked decline was observed from 19% in the depletion group to 3% with 1250 ppb cobalt, again demonstrating the importance of urinary excretion for controlling the cobalt content of the organism.

Effect of feeding mixed microbial culture fortified with trace minerals on ruminal fermentation, nutrient digestibility, nitrogen and trace mineral balance in Sheep

“…Absorbed cobalt is primarily excreted though the urine [ 39 ]. Cobalt concentrations were extremely low and not detectable in the present study.…”

Effects of different strategies of mineral supplementation (marine algae alone or combined with rumen boluses) in organic dairy systems

“…Iodine, Se and Co serum concentrations show a good response to dietary supplementation (Franke et al, 2009;Sch€ one et al, 2009;Cook and Green, 2010). The homoeostatic control of these elements is mainly mediated by urinary excretion: they are absorbed from the intestinal tract at high rates without a homoeostatic control (Kirchgessner et al, 1994(Kirchgessner et al, , 1997(Kirchgessner et al, , 1999. Mineral concentrations in milk are presented in Table 4.…”

Scientific Opinion on the use of cobalt compounds as additives in animal nutrition

“…Absorbed Co is primarily excreted by urine but small amounts appear to be excreted by endogenous Co recycling into digestive tract (Kirchgessner et al, 1994). Absorbed Co is primarily excreted by urine but small amounts appear to be excreted by endogenous Co recycling into digestive tract (Kirchgessner et al, 1994).…”

“…In laboratory animals such as rats and mice, the reported apparent absorption of Co from Co-chloride was in a range 13 to 34 % whereas Co from insoluble Co oxide showed 1 to 3 % absorption rate only (Kirchgessner et al, 1994;. In rats and guinea pigs it has been suggested that Co absorption may decline with age (Naylor and Harrison, 1995).…”

“…Faecal elimination is the major route of Co excretion following oral intake. Absorbed Co is primarily excreted by urine but small amounts appear to be excreted by endogenous Co recycling into digestive tract (Kirchgessner et al, 1994). Within 70 days after oral administration of 60 Co in a form of Cochloride to lactating dairy cows, the excretion of labeled metal by faeces, urine and milk was 97, 0.26 and 0.01 %, respectively (Van Bruwaene et al, 1984).…”