Stage of maturity, processing, and hybrid effects on ruminal in situ disappearance of whole-plant corn silage

Five in situ trials with whole-plant corn silage (WPCS) were conducted in two ruminallycannulated Holstein cows to determine 24-h ruminal disappearance of dry matter (DM), starch, and neutral detergent ®ber (NDF). In Trial 1, the effect of maturity of WPCS on ruminal nutrient disappearance was evaluated. Treatments were early dent (ED), 1/4 milk-line (1/4 ML), 2/3 milkline (2/3 ML), and black-layer (BL) stage of maturity. Ruminal disappearance of DM was lower (p<0.01) for BL (474 g/kg) than ED (547 g/kg), 1/4 ML (579 g/kg), or 2/3 ML (530 g/kg). Ruminal starch disappearance was lower (p<0.01) for BL (862 g/kg) than ED, 1/4 ML, or 2/3 ML which averaged 950 g/kg. In Trial 2, the effect of mechanical processing of mature and immature WPCS and stover silage at harvest was evaluated. Processing increased (p<0.01) ruminal starch disappearance for both immature (844 vs. 664 g/kg) and mature (790 vs. 525 g/kg) WPCS. In Trial 3, two WPCS hybrids (grain vs. leafy) at two plant populations (lowˆ59,000 or highˆ79,000 plants/ha) were evaluated. Type of hybrid or plant population did not affect DM or NDF disappearance. However, starch disappearance was higher (p<0.01) for the leafy hybrid (872 vs. 731 g/kg). In Trial 4, brown-midrib (BMR) corn harvested as WPCS was evaluated for ruminal nutrient disappearance versus a conventional grain hybrid. Ruminal DM (602 vs. 561 g/kg) and NDF (326 vs. 220 g/kg) disappearance were higher (p<0.01) for BMR. In Trial 5, ruminal nutrient disappearance of highand low-NDF corn silage hybrids were compared. Ruminal DM (662 vs. 620 g/kg) and starch (987 vs. 950 g/kg) disappearance were higher, but NDF disappearance was lower (176 vs. 225 g/kg) for the low-NDF hybrid (p<0.001). In summary, delaying silage harvest to BL reduced ruminal nutrient disappearance. Mechanical processing increased ruminal disappearAnimal Feed Science and Technology 86 (2000) 83±94 * Corresponding author. Tel.: ‡1-608-263-3491; fax: ‡1-608-263-9412. E-mail address: [email protected] (R.D. Shaver) 0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 7 8 4 0 1 ( 0 0 ) 0 0 1 6 3 2 ance of WPCS, primarily through greater ruminal starch disappearance. Ruminal starch and NDF disappearance were higher for leafy and BMR hybrids, respectively, relative to a conventional grain hybrid. Ruminal DM disappearance was increased for a low-NDF hybrid, but effects were positive for starch and negative for NDF disappearance. # 2000 Elsevier Science B.V. All rights reserved.