2007 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.
This report documents research conducted under a specific cooperative agreement between ARS and Cornell University. Additional details of research can be found in the report for the in-house associated project 1907-31000-005-00D, Alternative Mechanisms for Improving Ruminal Fermentation. Ruminal lysine degradation is a wasteful process that deprives the animal of an essential amino acid. Non-lactating dairy cattle (n =.
3)that were fed a diet of timothy hay had 2 h post-feeding volatile fatty acid concentrations of 62.3 plus or minus 3.2 mM acetate, 18.3 plus or minus 3.5 mM propionate and 8.7 plus or minus 0.6 mM butyrate. The ammonia concentration was 4.5 plus or minus 1.4 mM, and pH was 6.2 plus or minus 0.1. When mixed ruminal bacteria from cattle fed timothy hay were incubated with lysine in vitro, the extent of the degradation was concentration-dependent. A significant fraction of lysine was left un-degraded when the concentration was increased, and the ability of the bacteria to deaminate lysine could be saturated. Serial dilutions (10-fold increments, n =3) of the mixed ruminal bacteria into basal medium with lysine as an energy source had dense growth (> 0.7 optical density) and high concentrations of ammonia (>50 mM) but only at dilutions less than or equal to one million. Some growth and ammonia were detected in higher dilutions, but a sharp transition from growth to no growth was not observed. Cattle that were fed lysine (70 g per day), commercial protein supplement and timothy hay had post-feeding volatile fatty acid concentrations of 76.3 plus or minus 4.6 mM acetate, 18.8 plus or minus 1.2 mM propionate and 8.5 plus or minus 0.6 mM butyrate. In this case, ammonia concentration was 8.5 plus or minus 0.7 mM and pH was 6.5 plus or minus 0.2. Mixed ruminal bacteria from the supplemented cattle did not have a greater capacity to degrade lysine than those obtained from cattle fed only hay, and dietary lysine supplementation did not enhance the numbers of bacteria that could utilize lysine as a sole energy source. These results indicate that mixed ruminal bacteria can be saturated with lysine. Un-degraded lysine would escape ruminal degradation and enter the small intestine, but it is unlikely that this amount of lysine necessary to achieve this by-pass would be cost effective. The ADODR and Cooperator have met regularly to discuss the state and progress of the project/agreement.