Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 18, 2009
Publication Date: October 30, 2009
Citation: Grabber, J.H. 2009. Forage Management Effects on Protein and Fiber Fractions, Protein Degradability, and Dry Matter Yield of Red Clover Conserved as Silage. Animal Feed Science And Technology. 154:284–291. Interpretive Summary: With adequate soil moisture, dry matter yields and forage quality of red clover can equal or exceed alfalfa in many temperate regions of the world. Unfortunately, milk production from cattle fed red clover is usually below expectations. This in part occurs because a portion of the protein in red clover is attached to molecules known as "o-quinones" and this can depress the intestinal digestion and absorption of amino acids by cattle. Poor performance may also occur because red clover does not contain enough readily degraded protein to support rapid growth of microbes in the rumen (the first compartment of a cow's stomach). These microbes are amazingly a major source of dietary protein for cattle. The primary objective of this study was to evaluate how cutting management influences the dry matter yield and protein quality of red clover harvested for feeding to dairy cattle. We found that commencing red clover harvests earlier in the spring than normal favorably increased the amount of rumen degradable protein and decreased the amount of protein protected by o-quinones. Fortunately, earlier cutting did not hurt total yearly forage production or survival of red clover plants. Further analysis of the data revealed that "dairy quality" red clover with desirable concentrations of fiber (~40%), crude protein (~20%), and rumen degradable protein (15%) could be obtained by taking a first harvest at a late vegetative growth stage, taking a second harvest when most plants are bud stage, and taking a third harvest when roughly one-third of plants are in bloom. Implementing these harvest management practices may improve milk production of cattle fed red clover and decrease the need for feeding expensive protein supplements.
Technical Abstract: Due to the action of o-quinones formed via polyphenol oxidase, conserved red clover (Trifolium pratense L.) contains abundant rumen undegradable protein (RUP), but inadequate rumen degradable protein (RDP) for dairy cattle. This study examined how forage management influences RDP, RUP, crude protein (CP) and fiber fractions in red clover silage and dry matter (DM) yields 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. After ensiling at 370 g/kg DM, CP and fiber were fractionated according to the Cornell Net Carbohydrate and Protein System (CNCPS). RDP and RUP were calculated from CNCPS fractions or estimated by a more convenient Streptomyces griseus protease procedure, which gave highly related (R2 = 0.95) estimates of CP degradability. Early cutting of red clover favorably decreased RUP, neutral detergent fiber (NDF), and acid detergent fiber (ADF) and increased RDP and CP in the first two harvests. Regression analyses indicated desirable levels of RDP (>150 g/kg DM) and NDF (~400 g/kg DM) 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. Averaged across harvest schedules, red clover had lower RDP, CP and ADF, higher RUP, and similar NDF compared to alfalfa. Total DM yields of red clover and alfalfa were not influenced by harvest schedule. Time of establishment had little effect on silage quality, but it did influence total DM yields; April vs. August seeding depressed red clover yields (12.3 vs 13.1 t/ha) but enhanced alfalfa yields (12.5 vs 11.9 t/ha) during the first full production year. Overall, these results suggest protein utilization and performance of dairy cattle could be moderately improved without sacrificing DM yield by taking a very early first cutting of red clover followed by regrowth cuttings made at progressively later maturities.