|Rotz, Clarence - Al|
|Hymes Fecht, Ursula|
Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/13/2004
Publication Date: 6/15/2004
Citation: Grabber, J.H., Broderick, G.A., Powell, J.M., Rotz, C.A., Ehlke, N.J., Davidson, C., Hymes Fecht, U.C., Massingill, L.J., Niemann, K.M., Vellekson, D. 2004. Impact of forage condensed tannins on protein utilization and nitrogen cycling on dairy farms: a progress report. In: American Forage and Grassland Council Conference Proceedings. Volume 13, June 12-16, 2004, Roanoke, Virginia. 2004 CDROM. Interpretive Summary:
Technical Abstract: Binding of condensed tannins to protein can moderate proteolysis in forages during ensiling, ruminal digestion, and decay of residues in soil. We are conducting forage quality, feeding, cropping, and manure management studies with tannin-free alfalfa and three birdsfoot trefoil populations containing about 1, 2 and 4% tannin to identify optimal forage tannin concentrations and management practices for improving protein and nitrogen use on dairy farms. Tannins and degree of conditioning each influenced the proportions of readily degraded, buffer-soluble protein (BSP) and protease degradable protein (PDP) in forages conserved as silage and hay. In conventionally conditioned silages and hays, low to high tannin trefoils had 4 to 14% less BSP and PDP than alfalfa. Compared to conventional conditioning, maceration of forages decreased the proportion of BSP by an average of 30% and PDP by 0 to 23%. Maceration lowered PDP to a greater degree in silage than in hay and in tannin-containing trefoils than in alfalfa. In the first of several planned lactation trials, total mixed rations formulated with 50% legume silage plus 10% corn silage and 40% concentrate had similar intakes but production of 3.5% fat-corrected milk was 5.3, 10.8, and 8.6 lb/day greater for low, medium, and high tannin trefoils, respectively, compared to alfalfa. In addition to greater milk production, levels of milk urea nitrogen were lowest in diets formulated with moderate and high tannin trefoil, indicating greater protein-use efficiency. Total nitrogen excretion in manure was similar among diets, but ratios of urinary to fecal nitrogen decreased from 60:40 to 40:60 as forage tannin levels increased; these shifts should decrease ammonia losses from manure. Ongoing field and laboratory trials will reveal how tannins influence the mineralization and uptake of nitrogen from manure and forage residues by sorghum-sudangrass. Previous farm-level simulations with the Integrated Farming Systems Model indicated that the use of a tannin-containing alfalfa on a Wisconsin dairy farm would increase long-term farm profitability up to 12% and reduce nitrogen losses up to 25%. After the model is refined with data from our current studies, simulations will be run for a variety of farming systems and farming regions to identify forage tannin levels and management practices that optimize the economic and environmental performance of dairy farms in the United States. Because of the potential economic and environmental benefits, we are partnering with other groups to develop alfalfa with optimal levels of tannins for use by dairy and other types of livestock farms.