FORAGE PROTEIN CHARACTERIZATION AND UTILIZATION FOR CATTLE

OBJECTIVES: Objective 1: Refinement and validation of methods for quantifying forage protein fractions, rates and extents of protein degradation, and extents of digestion of undegradable intake protein. Objective 2: Characterize genetic and environmental effects on forage protein fractions, rates and extents of protein degradation, and extents of digestion of undegradable intake protein.

APPROACH: Laboratory experiments will evaluate protease enzymes and NIRS for prediction of forage protein characteristics. Field experiments will evaluate genetic and environmental effects on forage protein characteristics.

PROGRESS: 1998/10 TO 2003/09
Near infrared reflectance spectroscopy (NIRS) is a cost-effective, instrumental method of determination of plant constituents. It accurately and rapidly predicts leaf and stem concentration and total ash and Ca, K, Mg, P, S., B, Cr, Mn, and Zn concentrations in sun-cured and oven-dried leaves and stems of alfalfa. Prediction equations need to be redeveloped to accurately be used for new populations of plant materials not originally included in developing the equations. The NIRS technique predicts CP and CP degradability of clovers and alfalfa from diverse environments and results were less variable than laboratory methods. The NIRS technique showed that rumen undegraded protein decreases with forage maturity and is less for an August than a June harvest. Illinois bundleflower is a warm-season perennial legume native to the grasslands of the central United States. Forage quality was evaluated in field and laboratory studies. Whole plant forage quality was highest at early flower in mid-July with average ADF, NDF, and CP of 320, 360, and 180 g kg-1, respectively. By mid-August , ADF and NDF had increased to 412 and 485 g kg-1 while CP decreased to 126 g kg-1. Leaf concentration decreased from 618 to 335 g kg-1 between early flower and late pod with leaf CP decreasing from 216 to 147 g kg-1. Whole plant IVDDM decreased with maturity from an average of 470 g kg-1 digestible dry matter at early flower to an average of 390 g kg-1 at late pod. Whole plant IVTD decreased from 648 g kg-1 at early flower to 560 g kg-1 at late pod. The low forage digestibility suggests anti-quality components such as tannin may be interfering with ruminal digestion. Nitrogen fertilization and ecotype had little effect on any component of forage quality, however, a higher cutting height consistently improved forage quality. Illinois Bundleflower has the potential to provide high quality forage during the summer slump in cool-season forage production. High rates of manure were applied to a newly seeded legume-grass mixture. Although, extensive leaching of soil nitrate occurred following manure application and the average forage nitrate concentration was only 1400 ppm, Canada thistle, pigweed, and lambsquarters contain nitrate concentrations exceeding 8000 ppm. Selective grazing of these species by ewes resulted in illness or death of 35% of the ewes due to nitrate poisoning. Improper manure disposal poses risks to environmental quality and animal health.

IMPACT: 1998/10 TO 2003/09
We first show that properly calibrated near infared reflectance spectroscopy is an effective tool for rapid and accurate analysis of forage mineral, leaf and stem proportion and protein fractions in forages. Because of its low cost, near Infrared reflectance spectorscopy provides an economic advantage over standard laboratory procedures. Illinois bundleflower is a native legume that can provide high quality forage for use in Midwest USA forage systems.

PUBLICATIONS: 1998/10 TO 2003/09
1. Fishbach, J., Peterson, P., Sheaffer, C., Ehlke, N., and Wyse, D. 2003. The summer forage potential of Illinois bundleflower in Minnesota. Agron. Abst. p. 322.
2. Schmidt, K.M., Russelle, M.P., Sheaffer, C.C., and Christians, C.J. 2003. Risks from high manure application before pasture restoration. P. 233-237. In Proc. American. Forage and grassl. Council. Lafayette, LA. 26-30 April 2003.