Activity of Dehydrogenases and Enzymes of Nitrogen Metabolism in Rumen Mucosa and Liver of Steers Fed . Monensin

Kalal!njuk G. I., M. Marounek, M. G. Gerasymiv, O. G. Savka, L. G. Kalal!njuk: Activity of Dehydrogenases and Enzymes of Nitrogen Metabolism in Rumen Mucosa and Liver of Steers Fed Monensin. Acta vet. Bmo, 62, 1993: 127-131. The effect of monensin on activity of intracellular enzymes of tissues was determined in ten steers fed hay, silage and concentrate. Five steers received monensin in amount of 0.5 mg per 1 kg of live weight per day. Mter 10 months steers were slaughtered and activity of dehydrogenases and enzymes of nitrogen metabolism assayed in mitochondrial and cytoplasmic fraction of cells of rumen mucosa and liver. Monensin had no consistent effect on activity of nine enzymes examined (lactate dehydrogenase, malate dehydrogenase, ex-ketoglutarate dehydrogenase, glutamate dehydrogenase, glutamin synthetase, arginase, ornithine carbamoyltransferase, aspartate aminotransferase and alanine aminotransferase). The results indicate that long-term inclusion of monensin into diet of steers has no damaging effect on cells of rumen mucosa and liver. Monensin, enzyme, rumen mucosa, liver ~onophores are fed to ruminants because they improve feed efficiency and increase weight gains. Numerous studies have demonstrated that ionophores alter rumen metabolism (review Bergen and Bates 1984). Typical ionophore-induced effects include the increase of propionate production in the rumen and the decrease of production of acetate, butyrate and methane. Similar changes in fermentation stoichiometry were observed in ruminant hindgut (Marounek et al. 1990). Recent research provided evidence for an effect of ionophores on metabolism in ruminants independent of alterations in rumen and hindgut microbial metabolism. Experiments of Davison (1984) showed that 36-40% of radiolabelled monensin was absorbed from the gastrointestinal tract of calves and Armstrong and Spears (1988) supplied data on changes of intermediary metabolism of heifers following intravenous ionophore administration. In this paper we examined the effect of long-term monensin feeding on activity of nine intracellular enzymes in rumen mucosa and liver of steers. . Materials and Methods Ten crossbred steers, one year old at the beginning of experiment were divided into two groups according to feed additive treatment. Steers were individually housed and kept on a diet consisting of concentrate (3.5 kg) and hay and silage ad libitum. Five steers received monensin in amount * Correst'Onding author