Submitted to: International Silage Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2009
Publication Date: 7/27/2009
Citation: Grabber, J.H. 2009. Harvest Management Effects on Crude Protein, Protein Fractions, Fiber and Yield of Dairy-quality Red Clover Conserved as Silage. In: Proceedings of the XVth International Silage Conference, July 27-29, 2009, Madison, Wisconsin. p 237-238.
Technical Abstract: Due to the action of protein-binding o-quinones, red clover (Trifolium pratense L.) contains abundant rumen undegradable protein (RUP), but inadequate rumen degradable protein (RDP) for rumen microbial protein synthesis. This study examined how harvest management influenced dry matter (DM) yields, crude protein (CP), RDP, RUP, and fiber in “dairy quality” red clover during the first full production year. In 2003 and 2006, red clover was cut early on 7 June or late on 14 June with two ~40 d regrowth cuts. For comparison, alfalfa (Medicago sativa L.) was cut early on 26 May with three ~32 d regrowth cuts, or late using the same schedule as early-cut red clover. Herbage ensiled at 370 g/kg DM was analyzed according to the Cornell Net Carbohydrate and Protein System (CNCPS) to calculate RDP and RUP. A simpler Streptomyces griseus protease procedure gave highly related (r2 > 0.95) but biased predictions of calculated RDP and RUP. The early harvest schedule improved the seasonal distribution of red clover yield, favorably decreased fiber and RUP, and increased CP and RDP in the 1st two cuts. Regression analyses indicated desirable levels of calculated RDP (>150 g/kg DM) and neutral detergent fiber (NDF~400 g/kg DM) and could be obtained by harvesting red clover at a mean stage weight maturity of 2.0 at first cut, 3.0 at second cut, and 3.5 to 4.0 at third cut. Total DM yields of red clover and alfalfa during the production year were not influenced by harvest schedule, but they were affected by time of seeding; April vs. August seeding depressed red clover yields (12.3 vs 13.1 Mg/ha) but enhanced alfalfa yields (12.5 vs 11.9 Mg/ha). Averaged across harvest schedules and cuttings, red clover and alfalfa had similar NDF, but red clover had lower acid detergent fiber, CP, and RDP and higher RUP than alfalfa. Overall, forage species had a greater impact on protein quality parameters than harvest schedule. These results suggest protein utilization and performance of dairy cattle could be moderately improved by a very early first cutting of red clover followed by regrowth cuttings at progressively greater maturities.