Wednesday, November 15, 2006

Evaluation of Desmodium incanum Germplasm for Tannin Concentration.

Kenneth Quesenberry, Judith Dampier, and Maria Laura Vidoz. Univ of Florida, PO Box 110500, Gainesville, FL 32611-0500

Incorporation of forage legumes into grazing systems is one method of improving the nutritive value of the sward.  The genus Desmodium is native to both SE Asia and new world tropics and subtropics. Most of the species developed as forages are from the tropical areas (e.g., D. heterocarpon ssp. ovalifolium, D. intortum, D. heterophyllum, D. uncinatum) and lack frost tolerance.  Desmodium incanum is a perennial species that is native to subtropical and tropical South America but has become widely naturalized in subtropical Florida.  It tolerates close grazing but available material has limited use for cattle due to concerns related to tannin content.  Additionally the development of persistent material with moderate tannin levels may fill a current forage gap in small ruminant production, particularly the expanding meat goat industry, in the southeastern US and the US Virgin Islands.  Low to moderate amounts of tannin can be beneficial for both cattle and small ruminant.  Lower levels of condensed tannins have been shown to effectively bind protein thus reducing the amount of rumen bypass protein and thereby enhancing the nutritive value of the forage. Tannin concentrations were evaluated in 32 D. incanum germplasm accessions grown under field conditions in North Florida. Mature leaves from the upper portion of the plant canopy were hand harvested, extracted fresh in acetone for 24 h.  Radial diffusion assays as per the protocol of Hagerman for tannin concentration were conducted in the summer of 2005, using tannic acid as a reference standard.  Tannin concentrations among D. incanum accessions varied widely.  Percent tannin ranged from a low 0.4% to a high of 5.9% with no predominant value evident.  Variability in tannin concentration did not appear to be associated with geographic area of origin.   

Handout (.pdf format, 150.0 kb)