caa a22 4500 386322813 CHVBK 20180307111632.0 cr unu---uuuuu 161130e198803 xx s 000 0 eng 10.1079/BJN19880037 doi S0007114588000388 pii (NATIONALLICENCE)cambridge-10.1079/BJN19880037 Effect of nitrate and its reduction products on the growth and activity of the rumen microbial population [Elektronische Daten] 1. The nature of the digestion-inhibiting substance in Kikuyu grass (Pennisetum clandestinum, Hochst), containing high levels of nitrate, was investigated using in vitro digestibility techniques. 2. Nitrite, which accumulated during the reduction of nitrate to ammonia, seemed to be the primary factor reducing digestibility. Nitrate and ammonia did not affect digestion in vitro. 3. Nitrite caused a reduction in the cellulolytic, xylanolytic and total microbial population, with a concomitant reduction in cellulase and xylanase activity of the digesta. 4. The mode of action of nitrite on rumen microbial growth was investigated. 5. The possibility that the growth of cellulolytic rumen microbes was depressed by a reduction in concentration of essential branched-chain volatile fatty acids by nitrite was discounted. 6. Although nitrite caused a marked increase in the redox potential, due to its oxidizing properties, the more-positive redox potential did not reduce the digestibility of the grass. 7. The growth of three of the four major cellulolytic bacteria commonly found in the rumen was severely depressed by nitrite, while some rumen bacteria were relatively insensitive to nitrite. 8. Growth inhibition seemed to depend primarily on the extent to which these microbes derive their energy from electron-transport-mediated processes. 9. It was suggested that, due to the sensitivity of some rumen bacteria to nitrite, digestibility and therefore animal performance could be affected long before clinical symptoms of nitrite toxicity become apparent. Copyright © The Nutrition Society 1988 Marais J. P. Cedara Agricultural Research Institute, Pietermaritzburg, South Africa Therion Joha J. Animal and Dairy Science Research Institute, Irene, South Africa Mackie R. I. Animal and Dairy Science Research Institute, Irene, South Africa Kistner A. Laboratory of Molecular and Cell Biology, CSIR, Pretoria, South Africa Dennison C. Department of Biochemistry, University of Natal, Pietermaritzburg, South Africa British Journal of Nutrition Cambridge University Press 59/2(1988-03), 301-313 0007-1145 59:2<301 1988 59 BJN https://doi.org/10.1079/BJN19880037 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1079/BJN19880037 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Marais J. P. Cedara Agricultural Research Institute, Pietermaritzburg, South Africa NATIONALLICENCE 700 1- Therion Joha J. Animal and Dairy Science Research Institute, Irene, South Africa NATIONALLICENCE 700 1- Mackie R. I. Animal and Dairy Science Research Institute, Irene, South Africa NATIONALLICENCE 700 1- Kistner A. Laboratory of Molecular and Cell Biology, CSIR, Pretoria, South Africa NATIONALLICENCE 700 1- Dennison C. Department of Biochemistry, University of Natal, Pietermaritzburg, South Africa NATIONALLICENCE 773 0- British Journal of Nutrition Cambridge University Press 59/2(1988-03), 301-313 0007-1145 59:2<301 1988 59 BJN CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge