Effect of monensin on the fermentation of basal rations in the Rumen Simulation Technique (Rusitec)

Abstract

1. A long-term experiment was made with the Rumen Simulation Technique (Rusitec), in which the fermentation of a mixed ration of hay (10 g/d) and bruised barley (5 g/d) was compared with the fermentation of the same diet in the presence of 2, 10 and 50 mg monensin/d. 2. Monensin depressed the production of acetic and butyric acids, markedly increased the production of propionic acid and virtually, eliminated the production of isovaleric acid. The production of methane was decreased in the presence of monensin, but this decrease could be accounted for entirely by the changes in the production of volatile fatty acids and redistribution of metabolic hydrogen. 3. The digestibility of dry matter (DM) in the rations declined in the presence of monensin. Determinations of the rates of digestion showed that the digestion of the readily-fermented food in the initial stages was not affected by monensin, but that at 24 h digestion had been inhibited by monensin. The inhibition was due entirely to its effect on the digestion of the fibrous components. Digestion of non-fibrous material was not affected. 4. The efficiency of microbial growth, expressed as g dry weight/mol ATP formed (YATP) and in terms of DM digested, tended to be increased by monensin. This however occurred only at high, non-practical doses. 5. Urease (EC 3. 5. 1. 5) was induced by the addition of urea of the fermentation, but monensin had no effect on urease activity. Although monensin increased the activity of protease in washed suspensions, more food protein apparently escaped degradation. This may have been due to decreased deaminative activity. 6. Monensin altered the microscopic appearance of the fermentation fluid, and changed the activity of some enzymes in sonicated extracts, including alkaline phosphatase (EC 3. 1. 3. 1), acetate kinase (EC 2. 7. 2. 1) and succinate dehydrogenase (EC 1. 3. 99. 1). These results are discussed in terms of known sensitivities of rumen microbes to monensin and their contribution to the fermentation as a whole.

Effects of salinomycin and vitamin B6 on in vitro metabolism of phenylalanine and its related compounds by ruminal bacteria, protozoa and their mixture.

“…SL caused a dramatic decline in deaminase activity (McAllister et al, 1994). Similar changes have been observed with other ionophores (Hino and Russell, 1985;Newbold et al, 1990;Russell and Martin, 1984;Van Nevel and Demeyer, 1977;Wallace et al, 1981;Yang and Russell, 1993a, b). Amino acid deamination has been discussed to be particularly sensitive to ionophores due partly to the elimination of a specific bacterial population of amino acid utilizers (Yang and Russell, 1993a) and to the decreased deaminative activity of ionophore-resistant bacteria (Newbold et al, 1990).…”

“…Deamination determines the rate of ruminal amino acid degradation (Annison et al, 1959;Lewis, 1962). SL has been shown to decrease amino acid breakdown (Hoshino et al, 1992;Okuuchi et al, 1993), and this may be due to the inhibitory effect of deamination as has been observed with other ionophores (Hino and Russell, 1985;Newbold et al, 1990;Russell and Martin, 1984;Van Nevel and Demeyer, 1977;Wallace et al, 1981). In the case of tryptophan metabolism, Okuuchi et al (1993) reported that tryptophan production from indolepyruvic acid in all the rumen bacterial and protozoal suspensions was greatly enhanced by SL, but skatole and indole production from tryptophan by SL were completely inhibited in the rumen bacterial suspensions.…”

Effects of hydrolysed yeasts on ruminal fermentation in the rumen simulation technique (Rusitec)

“…Three incubation trials were carried out independently using six Rusitec fermentation vessels. Experimental procedures similar to those reported by Wallace et al (1981), Durix et al (1991) and Breves et al (2000) were used in these trials. In Experiment 1, six vessels of the Rusitec system were run for a total period of 22 days.…”

Effect of Monensin on Production of Volatile Fatty Acids from Cellulose, Hemicelluloses, Pectin and Starch in Mixed Cultures of Rumen Microorganisms

“…While considerable research has been reported on how rumen fermentation is affected by monensin, information is limited on how this polyether ionophore affects the fermentation of particular components of plant cell material. Some experiments in vivo and in vitro have shown that monensin decreases the digestibility of fibre and fibrous components (Poos et al 1979;Henderson et al 1981;Wallace et al 1981;Whetstone et al 1981). Also salinomycin, an ionophore similar to monensin, has been shown to depress the digestibility of fibre (Zinn 1986).…”