CONDENSED TANNIN AND POLYPHENOL INTERACTIONS WITH FORAGE PROTEIN AS INFLUENCED BY THE SEVERITY OF MECHANICAL CONDITIONING

Authors: Grabber, John; DAVIDSON, CHRISTY - UW MADISON; Massingill, Lee

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2004
Publication Date: 11/2/2004
Citation: Grabber, J.H., Davidson, C., Massingill, L.J. 2004. Condensed tannin and polyphenol interactions with forage protein as influenced by the severity of mechanical conditioning [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. CDROM.

Interpretive Summary:

Technical Abstract: The severity of conditioning may alter N fractions in forages, particularly if protein-binding tannins and polyphenols are present. In 2002 and 2003, cuttings of alfalfa, birdsfoot trefoil, and red clover were conventionally conditioned or severely macerated and then conserved as silage and hay. Forages were analyzed for buffer-soluble N (BSN), protease degradable N (PDN), and protease undegradable N (PUN). Averaged over conservation methods, N fractions of conditioned alfalfa were comprised of 734 g/kg of BSN, 67 g/kg of PDN, and 199 g/kg of PUN. Low to high tannin populations of trefoil had 9 to 69 kg/g less BSN, 20 to 29 g/kg less PDN, and 29 to 97 kg/g more PUN than alfalfa. In contrast, red clover with polyphenols had 163 g/kg less BSN, 37 g/kg more PDN, and 126 g/kg more PUN than alfalfa. Macerated forages had 145 g/kg less BSN than conditioned forages. Maceration increased PDN by 103 g/kg in alfalfa, 49 g/kg in trefoil, and 179 g/kg in red clover. Maceration increased PUN by 38 g/kg in alfalfa and by 88 to 110 g/kg in trefoil but PUN in red clover was decreased by 43g/kg. The results indicate that maceration and tannins acted synergistically to reduce protein solubility and degradability. Polyphenols in conditioned and macerated red clover dramatically reduced protein solubility but reductions in proteolysis were less pronounced after maceration than after conditioning.