RUMINAL LYSINE DEGRADATION
Plant, Soil and Nutrition Research
2008 Annual Report
1a.Objectives (from AD-416)
1). To isolate and identify ruminal bacteria responsible for ruminal lysine degradation. 2). To study the effect of the feed additive, monensin, and bacteriocins on lysine degradation.
1b.Approach (from AD-416)
Lysine is often an amino acid that limits milk production, but bacteria responsible for wasteful ruminal lysine degradation have not yet been identified. Mixed ruminal bacteria will be enriched with lysine in vitro, and bacteria capable of utilizing lysine will be isolated, characterized physiologically, tested for their susceptibility to monensin and bacteriocins, and identified via 16 S rDNA sequencing. Cattle will be supplemented with lysine to see if these same bacteria increase in vitro. The experiments with live cattle have been completed and cow is no longer needed. The manuscript entitled "Cattle will be supplemented with lysine to see if these same bacteria increase in vitro," was submitted one year ago and has been accepted.
Ruminal lysine degradation is a wasteful process that deprives the animal of an essential amino acid. Clostridium sticklandii is a Gram-positive, obligate amino acid fermenting ruminal bacteria that degrades lysine at a rapid rate. Previous work indicated that C. sticklandii could be inhibited by the feed additive monensin, but this antibiotic has been banned by the European Union as a growth promotant in feed. A similar ban is being considered in the United States. Some ruminal bacteria produce peptides (bacteriocins) that inhibit gram-positive bacteria, and bacteriocins have been proposed as an alternative to antibiotics. Our work showed that approximately 50% of Streptococcus bovis strains isolated from the rumen had antimicrobial activity, but some strains were distinctly more active. S. bovis HC5 was the best strain, and its bacteriocin (bovicin HC5) strongly inhibited the ammonia production of mixed ruminal bacteria and C. sticklandii. The potential use of bovicin HC5 in the rumen was complicated by the fact that it can be degraded by the extracellular peptidases and proteinases of ruminal fluid. However, our most recent work demonstrated that most of the bovicin HC5 activity remained cell-associated. Because the cell-associated bovicin HC5 was much more resistant to degradation by peptidases and proteinases, naturally occurring bacteriocins have the potential to inhibit lysine degrading bacteria such as C. sticklandii and protect this nutritionally important amino acid. The ADODR or Cooperator have met regularly to discuss the state and progress of the project/agreement.
Problem Statement 2C: Improving Efficiency of Nutrient Utilization and Conversion to Animal Products of the NP101 Action Plan Animal Production and Well-Being Action Plan (2007-2012)