Forage management effects on protein and fiber fractions, protein degradability, and dry matter yield of red clover conserved as silage

Dueto theactionofo-quinones formedviapolyphenoloxidase, conserved red clover (Trifolium pratense L.) contains abundant rumen undegradable protein (RUP), but inadequate rumen degradable protein (RDP) fordairy cattle. This studyexaminedhowforagemanagement 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 ∼40d regrowth cuts. For comparison, alfalfa (Medicago sativa L.) was cut early on 26 May with three ∼32d regrowth cuts or late using the same schedule as early cut red clover. After ensiling at 370g/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 proteaseprocedure,whichgavehighly 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 (>150g/kg DM) and NDF (∼400g/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 3.5–4.0 at third cut. Averaged across harvest schedules, red clover had lower RDP, CP and ADF, higher RUP, and similar NDF Abbreviations: ADF, acid detergent fiber; ADIP, acid-detergent insoluble protein; B1, buffer-soluble protein precipitated by tungstic acid; B2, buffer-insoluble protein extracted with neutral detergent; B3, neutral detergent insoluble protein extracted with acid detergent; CNCPS, Cornell Net Carbohydrate and Protein System; CP, crude protein; DM, dry matter; NDF, neutral detergent fiber; NDIP, neutral-detergent insoluble protein; MSW, mean stage weight; RDP, rumen-degradable protein; RUP, rumen-undegradable protein. ∗ Tel.: +1 608 890 0059; fax: +1 608 890 0076. E-mail address: [email protected]. 0377-8401/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.anifeedsci.2009.09.011 J.H. Grabber / Animal Feed Science and Technology 154 (2009) 284–291 285 compared to alfalfa. Total DM yields of red clover and alfalfa were not influenced byharvest schedule. Time of establishment had little effect on silage quality, but it did influence total DMyields; April vs. August seeding depressed red clover yields (12.3 t/ha vs. 13.1 t/ha) but enhanced alfalfa yields (12.5 t/ha vs. 11.9 t/ha) during the first full production year. Overall, these results suggest protein utilization and performance of dairy cattle could bemoderately improved without sacrificingDMyieldby takingaveryearlyfirst cuttingof red clover followed by regrowth cuttings made at progressively later maturities. Published by Elsevier B.V.