Relationships between kernel vitreousness and dry matter degradability for diverse corn germplasm II. Ruminal and post-ruminal degradabilities

Correlations between kernel vitreousness and ruminal in situ (RDMD) and total tract dry matter (TDMD; sum of ruminal in situ and post-ruminal in vitro measurements) degradabilities were determined for 33 diverse corn germplasm sources. These included a wide range of endosperm characteristics from opaque 2 (o2) types to densely packed flint types, and a number of intermediates. Harvests were done at two growth stages; 1/2 milk-line (ML) and black-layer (BL). Kernels from middle portion of ears were oven dried at 40 ◦C for 72 h and ground through a Wiley mill (6 mm screen) for measurement of in situ RDMD after 0 and 14 h of incubation using two steers (1.5 g/bag× 8 replicates per time point per steer in 5 cm× 5 cm bags of 50 m pore size). Residue from the 14 h bags proceeded to an 8 h in vitro enzymatic post-ruminal digestion after which the residue was oven dried at 62 ◦C for 48 h and dry matter content determined. Inbred by harvest-stage interactions were observed for 0-h disappearance and TDMD. Vitreousness had strong negative correlations with degradability Abbreviations: A-fraction, zero-hour disappearance or bag wash loss; BL, black-layer harvesting stage; DT, drying technique; GEM, Germplasm Enhancement of Maize project; HS, harvest stage; ML, 1/2 milk-line harvesting stage; NIRS, near infrared reflectance spectroscopy; pRDMD, post-ruminal dry matter degradability; RDMD, ruminal dry matter degradability; TDMD, total dry matter degradability; TSTARCHD, total tract starch degradability; WQS C2, Wisconsin quality synthetic cycle 2. ∗ Corresponding author. Current address: Monsanto Company, 3302 SE Convenience Blvd, Ankeny, IA 50021, USA. Tel.: +1 608 217 6085; fax: +1 515 963 4242. E-mail address: [email protected] (D. Ngonyamo-Majee). 0377-8401/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2007.09.001 260 D. Ngonyamo-Majee et al. / Animal Feed Science and Technology 142 (2008) 259–274 measurements, particularly for more mature (BL) samples (−0.728, −0.770 and −0.603) versus ML (−0.569, −0.541 and −0.338) for 0 h disappearance, RDMD and TDMD, respectively. Vitreousness was highly correlated with corn degradability, especially at a black-layer stage of harvest, in this diverse corn germplasm. © 2007 Elsevier B.V. All rights reserved.