Some effects of potassium chlorate administration onin vitroandin vivorumen fermentation

Abstract

Hay was fed to an in vitro continuous culture of the rumen microbial population and to sheep kept in metabolism cages, and the effects of potassium chlorate addition on the rumen fermentation were studied. The compound was given for 8 days in vitro and for either 3 or 8 days in vivo.Potassium chlorate addition in vitro (13-7 mg/g hay D.M.) depressed the production of CH 4 and acetate, had little effect on propionate production and caused a small increase in the production of w-butyrate and w-valerate. The treatment also depressed cellulose digestion and the concentration of DNA in fermentor liquor, but increased the CO a :CH 4 ratio in fermentor gas.When given in vivo for 8 days at 6-7 mg/g hay D.M., potassium chlorate progressively depressed total VFA concentration in rumen fluid, had no effect on VFA molar proportions but caused a small increase in the CO 2 :CH 4 ratio in rumen gas. When administered in vivo for 3 days at 14-4-15-3 mg/g hay D.M. the treatment increased the molar proportions of propionate and depressed those of acetate in rumen fluid without affecting total VFA concentration. There were considerable differences between animals in propionate response, and the maximum responses were generally obtained 2-5 days after dosing had ceased. Potassium chlorate addition also caused a temporary reduction in appetite with some sheep.It was concluded that potassium chlorate was toxic to the rumen microbial population when given for 8 days, but that large doses given over 3 days could be used to increase the ratio of propionic acid relative to acetic and butyric acids produced from • the rumen fermentation.

The in vitro reduction of sodium [36Cl]chlorate in bovine ruminal fluid1,2

“…They also found that the oxidation reduction potential of in vivo ruminal fluid in response to daily (for 8 d) potassium chlorate dosing increased for the first 4 d and then returned to a predosing baseline (Barry et al, 1978). Short-term (3 d) larger doses increased oxidation state at first (d 1) but then caused a reducing state lower than baseline that persisted several days beyond discontinuation of chlorate dosing (Barry et al, 1978). Barry et al (1978) concluded that long-term (8 d) administration of potassium chlorate is toxic to rumen microorganisms but that relatively large doses can be given for short periods (3 d).…”

“…The fact that in vitro DM digestibilities were not affected by either dose of chlorate suggests that the majority of commensal ruminal microorganisms were not adversely affected by chlorate. Barry et al (1978) found that in vitro ruminal cellulose digestion was decreased by 500 mg/L of potassium chlorate (1.4 to 5.0% compared with 9.2 to 11.1% disappearance of cotton thread with and without chlorate, respectively). Several other studies have shown that chlorate administration does not affect total culturable anaerobes present in the gastrointestinal tract, including the rumen (Anderson et al, 2001a,b;Callaway et al, 2002), but we cannot, with the available data from our study, speculate on how chlorate may have shifted the proportions of these ruminal commensal populations.…”

“…The additional chlorate reduction observed in live ruminal fluid may be due to bacterial reduction or to a continual production of reductants by live bacteria, whereas the reducing equivalents in autoclaved ruminal fluid could have been limiting. Barry et al (1978) reported that in vitro, daily addition of 500 mg/L of potassium chlorate increased the oxidation reduction potential of ruminal fluid day by day and that on a daily basis the oxidation reduction potential was greatest immediately after addition of chlorate. They also found that the oxidation reduction potential of in vivo ruminal fluid in response to daily (for 8 d) potassium chlorate dosing increased for the first 4 d and then returned to a predosing baseline (Barry et al, 1978).…”

“…Barry et al (1978) reported that in vitro, daily addition of 500 mg/L of potassium chlorate increased the oxidation reduction potential of ruminal fluid day by day and that on a daily basis the oxidation reduction potential was greatest immediately after addition of chlorate. They also found that the oxidation reduction potential of in vivo ruminal fluid in response to daily (for 8 d) potassium chlorate dosing increased for the first 4 d and then returned to a predosing baseline (Barry et al, 1978). Short-term (3 d) larger doses increased oxidation state at first (d 1) but then caused a reducing state lower than baseline that persisted several days beyond discontinuation of chlorate dosing (Barry et al, 1978).…”

“…Short-term (3 d) larger doses increased oxidation state at first (d 1) but then caused a reducing state lower than baseline that persisted several days beyond discontinuation of chlorate dosing (Barry et al, 1978). Barry et al (1978) concluded that long-term (8 d) administration of potassium chlorate is toxic to rumen microorganisms but that relatively large doses can be given for short periods (3 d). They speculated that a decreased fermentation rate in vitro may have caused the more positive reduction potential after several days of incubation (Barry et al, 1978).…”