ARS | Publication request: In-situ Ruminal Protein, Fiber, and Dry Matter Degradability of Legume Silages and Hays as Influenced by Protein-binding Polyphenols and Conditioning Methods

Submitted to: International Silage Conference
Publication Type: Proceedings
Publication Acceptance Date: June 8, 2009
Publication Date: July 27, 2009
Citation: Grabber, J.H., Coblentz, W.K. 2009. In-situ Ruminal Protein, Fiber, and Dry Matter Degradability of Legume Silages and Hays as Influenced by Protein-binding Polyphenols and Conditioning Methods. In: Proceedings of the XVth International Silage Conference, July 27-29, 2009, Madison, Wisconsin. p. 131-132.

Technical Abstract: Conditioning and conservation methods may alter polyphenol binding in forage legumes and the degradability of crude protein (CP), neutral detergent fiber (NDF) and dry matter (DM) in the rumen. In this study, alfalfa, birdsfoot trefoil with 6 or 15 g/kg condensed tannins (CT), and red clover with ~15 g/kg o-diphenols were roll conditioned or macerated, and conserved as silage or hay. Forages were characterized according to the Cornell Net Carbohydrate and Protein System (CNCPS) and incubated in situ for 0 to 72 h to determine the kinetics and ruminal disappearance (RD) of CP, NDF, and DM at a passage rate of 0.06/h. CP concentrations averaged 236 g/kg and NDF in roll-conditioned hay and silage averaged 414 g/kg in alfalfa and trefoil compared to 360 g/kg in clover. Maceration increased NDF in all forages to 430 g/kg. Polyphenols, conditioning and conservation methods primarily altered CNCPS fractions, degradation kinetics, and the RD of CP. The RD of CP averaged 725 g/kg and was 107 g/kg lower in high CT trefoil and clover than in alfalfa, 65 g/kg less in macerated than in roll-conditioned forage, and 147 g/kg less in hay than in silage. The impact of polyphenols on the RD of CP was minimally influenced by conditioning and conservation methods. Inversely related to lignin content, the average RD of NDF was greatest for clover (365 g/kg) and lowest for high CT trefoil (226 g/kg). While other forages were minimally affected, the RD of NDF in clover was increased 65 g/kg by maceration and 78 g/kg by conservation as silage. Average RD of DM was also greatest for clover (619 g/kg) and lowest for high CT trefoil (567 g/kg) and greater for silage (621 g/kg) rather than for hay (573 g/kg), but not influenced by conditioning method. In conclusion, polyphenols, conditioning and conservation methods acted independently to mainly influence the RD of CP in forage legumes.