Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2009
Publication Date: June 21, 2009
Citation: Grabber, J.H. 2009. Cutting Management Effects on Yield, Fiber, and Protein Degradability of Red Clover Conserved as Silage. In: Proceedings of the the 2009 American Forage and Grassland Council Annual Conference, June 21-24, 2009, Grand Rapids, Michigan. 2009 CDROM. Technical Abstract: With adequate soil moisture, forage yields of red clover can equal or exceed alfalfa in many temperate regions. Red clover also boasts superior fiber digestibility and greater rumen-undegradable protein than alfalfa, but milk yields from cattle fed red clover diets are often below expectations. Coupling of o-quinones to amino acids—responsible for low proteolysis in red clover—increases nitrogen excretion in manure, suggesting that intestinal amino acid absorption by cattle fed red clover may be depressed. Poor performance with red clover may in part occur because excessive rumen-undegradable protein could leave insufficient rumen-degradable protein for the synthesis of rumen-microbial proteins, a vital source of digestible protein for cattle. The objective of this study was to characterize how cutting management and season of growth influence dry matter yield and the concentrations of various crude protein fractions and fiber in “dairy quality” red clover. In 2003 and 2006 at a site near Prairie du Sac Wisconsin, primary growth of red clover was harvested on 6 June at an average mean stage weight (MSW) near 2.0 or one week later at a MSW near 3.0. Two additional harvests were then taken at about 40 d intervals. Herbage from each harvest was wilted, conserved in minisilos, and then analyzed for fiber and for various crude protein fractions using buffer, detergents, and a commercial Streptomyces griseus protease preparation. Total yields and persistence of red clover were similar for both cutting managements, but an earlier first harvest gave a more uniform seasonal distribution of yield. Regression analyses indicated that dairy quality forage with desirable dry matter concentrations of neutral detergent fiber (~40%), crude protein (~20%), and rumen-degradable protein (~15%) could be obtained if red clover is cut at a MSW of approximately 2.0 at first harvest, 3.0 at second harvest, and between 3.5 to 4.0 at third harvest. For growers, this would correspond to taking a first harvest when buds are just starting to appear, taking a second harvest when flowers are just starting to appear, and a third harvest when roughly one-third of red clover plants are in bloom. Taking an early first harvest at MSW 2.0 also kept dry matter concentrations of rumen-undegradable protein relatively low (~5%). In later harvests, dry matter concentrations of rumen-undegradable protein remained relatively high (~7.5%) regardless of plant maturity. This study suggests protein utilization and performance of dairy cattle fed red clover based diets might be improved if the first harvest of red clover is taken at a vegetative growth stage and followed by regrowth cuttings taken at progressively more mature growth stages.