Abstract
Three experiments were conducted to characterize lysine fermentation by Fusobacterium necrophorum, a ruminal bacterium that is known to degrade amino acids. In Experiment 1, 7 strains of Fusobacterium necrophorum were inoculated into media containing lysine (50 mM), lactate (50 mM), or lysine plus lactate (50 mM each) as the major energy substrate to evaluate growth and ammonia production. All strains grew with lysine, lactate, or lactate plus lysine as the primary substrate. When grown with lysine, all strains produced ammonia as an end product, even if lactate was also present. Smaller concentrations of ammonia for medium containing lactate plus lysine when compared with lysine alone indicate that the Fusobacterium strains used lactate as a growth substrate that stimulated utilization of ammonia. In Experiment 2, the 2 strains tested were able to degrade extensively both lysine and glutamic acid. Some evidence was detected for partial utilization for growth of histidine, methionine, and tryptophan by strain A21. In Experiment 3, the minimum inhibitory concentration (MIC) of the antibiotic tylosin was 25 μg/mL when Fusobacterium necrophorum strains A21 and B35 were grown in either lysine or lactate-enriched medium. The MIC of monensin was 6.25 and 3.9 μg/mL for strains A21 and B35, respectively, when grown in lysine-enriched medium, but > 50 and 10.9 μg/mL when the strains were grown in lactate-enriched medium. These findings may lead to ways that ruminal lysine degradation may be controlled.; Dairy Day, 2010, Kansas State University, Manhattan, KS, 2010; Dairy Research, 2010 is known as Dairy Day, 2010
Highlights
High milk-producing dairy cows require a well balanced supply of amino acids
In Experiment 1, 7 strains of Fusobacterium necrophorum were inoculated into media containing lysine (50 mM), lactate (50 mM), or lysine plus lactate (50 mM each) as the major energy substrate to evaluate growth and ammonia production
All strains grew with lysine, lactate, or lactate plus lysine as the primary substrate
Summary
High milk-producing dairy cows require a well balanced supply of amino acids. Lysine is often a limiting amino acid for dairy cows, especially when they are fed diets containing large amounts of corn proteins. Degradation of amino acids by ruminal microorganisms, makes it impossible to increase lysine supply to the cow by adding more lysine to the diet. Amino acids in the rumen are degraded by bacteria that are classified as hyper-ammonia producing bacteria, which exist in small numbers in the rumen but produce large amounts of ammonia by degradation of amino acids. Fusobacterium necrophorum has been identified as a hyper-ammonia producing bacterium. It has been isolated from rumen fluid enriched with lysine as a growth substrate, suggesting that Fusobacterium necrophorum may be one of the major bacteria that contributes to lysine degradation in the rumen
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