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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #57734
Title: EVALUATION OF IN SITU AND IN VIVO METHODS TO ESTIMATE RUMINAL PROTEIN AVAILABILITY OF BIRDSFOOT TREFOIL (LOTUS CORNICULATUS L.) VARYING IN CONDENSED TANNIN CONCENTRATION

Author
item ENDRES, MARCIA - UNIVERSITY OF MINNESOTA
item Jung, Hans Joachim
item STERN, MARSHALL - UNIVERSITY OF MINNESOTA
item EHLKE, NANCY - UNIVERSITY OF MINNESOTA

Submitted to: American Dairy Science Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Forage samples were used to study the effects of condensed tannin (CT) concentration on ruminal protein availability measured by various methods. Three genotypes of birdsfoot trefoil (Lotus corniculatus L.) low, medium and high tannin (4.3, 20.5, and 48.3 g CT/kg DM, respectively) and an alfalfa control were transplanted in a Waukegan silt loam soil type during Spring 1993. Two field plots of each genotype were harvested three times during the year at a similar stage of maturity (early bloom), resulting in six individual samples for each genotype. Total herbage was frozen immediately after being cut and freeze dried. After grinding, samples were taken for determination of ruminal CP availability by the in situ Dacron bag method and two in vitro methods - ficin protease and solubility in borate-phosphate buffer. No effect of CT concentration on ruminal CP degradation was observed when using the in situ procedure. In contrast, high tannin-birdsfoot trefoil (BFT) had lower (P<.05) CP degradation estimated by ficin protease and lower (P< .05) CP solubility in borate-phosphate buffer than low tannin-BFT. Treatment with polyethylene glycol, a compound that binds tannins, eliminated differences among genotypes, suggesting that the presence of CT on BFT samples was a major contributing factor to differences in CP availability. Regression of in situ results on ficin protease results was not significant (P= .21 ) with r=.26. Regression of ficin protease results on CT concentration was significant (P<.001) with r=.78. Based on these data, use of an in vitro technique, such as ficin protease, would be more appropriate than the in situ method for evaluation of differences in real CP availability among CT- containing forages.