Forage Quality Variation among Maize Inbreds: In Vitro Fiber Digestion Kinetics and Prediction with NIRS

The nutritive value of forage maize (Zea mays L.) may be improved through genetic selection for increased rate of fiber digestion or decreased indigestible fiber concentration. To identify sources of genetic variation, 45 maize inbreds were evaluated for in vitro neutral detergent fiber (NDF) digestion kinetic parameters using stem internode tissue harvested at silking during 2 yr. Near infrared reflectance spectroscopy (NIRS) was also used to estimate NDF digestion kinetic parameters. Maize inbreds varied significantly in NDF concentration and digestion kinetic parameters using either conventional in vitro analysis or NIRS predictions. Using NIRS predictions, inbreds varied in NDF concentration from 497 to 662 g kg -1 dry matter (DM), rate of NDF digestion ranged from 0.037 to 0.077 h -1 , and extent of NDF digestion was 525 to 735 g kg -1 NDF. The ranges for NIRS predicted parameters were less than those observed for the calibration data set by conventional analysis. Correspondence between conventional analysis data and NIRS predictions were good, except for lag time. Digestion kinetics calculated from NIRS predicted residues provided more precise predictions of lag time and fractional rate of digestion when compared with observations derived from conventional analyses, than did direct prediction of these kinetic parameters. Correlations between rate of NDF digestion and 18-h NDF digestibility (r = 0.79) or between potential extent of NDF digestion and 96-h NDF digestibility (r = 0.95) were large enough that these two fermentation intervals might substitute for conducting complete digestion kinetic studies with eight to 10 fermentation times. The substantial genetic variation among these maize inbreds shows good potential for development of silage hybrids with improved fiber digestion parameters. Year and year x genotype interactions were significant suggesting that identification of superior inbred lines will require evaluations in multiple environments.

[1]  Y. Barrière,et al.  Brown-midrib genes of maize: a review , 1993 .

[2]  G. C. Marten,et al.  Effect of the Brown Midrib-Allele on Maize Silage Quality and Yield 1 , 1983 .

[3]  G. C. Marten,et al.  Near infrared reflectance spectroscopy evaluation of ruminal fermentation and cellulase digestion of diverse forages , 1988 .

[4]  D. Buxton,et al.  Apparent inhibition to digestion by lignin in normal and brown midrib stems , 1992 .

[5]  V. L. Lechtenberg,et al.  Laboratory and in vitro Evaluation of Inbred and F2 Populations of Brown Midrib Mutants of Zea mays L. 1 , 1972 .

[6]  D. Buxton,et al.  Errors in forage-quality data predicted by near infrared reflectance spectroscopy , 1991 .

[7]  M. Motto,et al.  Effect of brown midrib-3 mutant on forage and yield in maize. , 1990 .

[8]  T. Lam,et al.  Lignin and Hydroxycinnamic Acids in Walls of Brown Midrib Mutants of Sorghum, Pearl Millet and Maize Stems , 1996 .

[9]  D. R. Buxton,et al.  Chemical and in vitro digestible dry matter composition of maize stalks after selection for stalk strength and stalk-rot resistance , 1986 .

[10]  D. Buxton,et al.  Environmental and Genetic Effects on Cell Wall Composition and Digestibility , 1993 .

[11]  D. R. Buxton,et al.  Forage quality variation among maize inbreds: in vitro digestibility and cell-wall components , 1994 .

[12]  D. Buxton,et al.  Maize Internode Elongation Patterns , 1994 .

[13]  V. L. Lechtenberg,et al.  Evaluation of a Brown Midrib Mutant of Zea Mays L. , 1972 .

[14]  K. Vogel,et al.  Comparison of In Vitro Dry Matter Digestibility and Cellulase Digestion for Deriving Near Infrared Reflectance Spectroscopy Calibration Equations Using Cool-Season Grasses , 1988 .

[15]  John S. Shenk,et al.  Populations Structuring of Near Infrared Spectra and Modified Partial Least Squares Regression , 1991 .

[16]  W. G. Pollmer,et al.  Variation and covariation in stover digestibility traits in diallel crosses of maize. , 1990 .

[17]  D. Mertens,et al.  Evaluating constraints on fiber digestion by rumen microbes. , 1988, The Journal of nutrition.