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United States Department of Agriculture

Agricultural Research Service

2012 Annual Report

1. Polyphenol oxidase improves protein utilization by ruminants. During ensiling, excessive protein degradation results in inefficient protein use and excessive nitrogen excretion when the silage is fed to ruminants. Polyphenol oxidase ([PPO] what causes browning in fruits like apples) can decrease protein degradation in plant extracts when combined with the right phenolic. ARS scientists in Madison, Wisconsin co-ensiled grasses, pairing a PPO grass with a high-phenolic grass (e.g., orchardgrass with tall fescue). Feeding trials with lambs indicated that total protein utilization by the lambs fed co-ensiled PPO grass with a phenolic grass improved 10-20% over control silages. Less nitrogen was excreted in the urine, indicating an increased utilization of protein. On average, at least $100 million is spent annually to supplement protein losses during ensiling. Incorporating a PPO/phenolic system during ensiling would create a $10-20 million economic advantage to dairy farmers each year due to a decreased need for protein supplements, and would also decrease nitrogen waste excretion into the environment.

2. New synthesis of natural compounds aids in the study of protein protection in forage plants. Red clover accumulates the phenolic, phaselic acid, in high levels. It is a key substrate for the enzyme, polyphenol oxidase (PPO), which is a natural system for post-harvest protein protection. ARS scientists in Madison, Wisconsin developed a streamlined laboratory synthesis for phaselic acid and related phenolics. These compounds are being used to investigate the biological pathway for phaselic acid production in alfalfa. Readily available phenolics related to PPO systems allow rapid advancement of knowledge that will lead to successful incorporation of a PPO/phenolic protein protection system in alfalfa. At present, this information is most useful to other scientists working on new avenues for silage treatment which would lead to a reduction in the cost of additional protein supplements and substantially less nitrogen waste from ruminant animal systems that would end up in the environment.

Review Publications
Wang, Z., Li, R., Xu, J., Marita, J.M., Hatfield, R.D., Qu, R., Cheng, J.J. 2012. Sodium hydroxide pretreatment of genetically modified switchgrass for improved enzymatic release of sugars. Bioresource Technology. 110:364-370.

Lee, M.R., Tweed, J.K., Sullivan, M.L. 2013. Oxidation of ortho-diphenols in red clover with and without polyphenol oxidase (PPO) activity and their role in PPO activation and inactivation. Grass and Forage Science. 68(1):83-92.

Sullivan, M.L., Zeller, W.E. 2012. Efficacy of various naturally occurring caffeic acid derivatives in preventing post-harvest protein losses in forages. Journal of the Science of Food and Agriculture. 93:219-226.

Last Modified: 4/19/2014
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