Abstract
BACKGROUNDThe relationship between the chemical and molecular properties – in particular the (acid detergent) lignin (ADL) content and composition expressed as the ratio between syringyl and guaiacyl compounds (S:G ratio) – of maize stems and in vitro gas production was studied in order to determine which is more important in the degradability of maize stem cell walls in the rumen of ruminants. Different internodes from two contrasting maize cultivars (Ambrosini and Aastar) were harvested during the growing season.RESULTSThe ADL content decreased with greater internode number within the stem, whereas the ADL content fluctuated during the season for both cultivars. The S:G ratio was lower in younger tissue (greater internode number or earlier harvest date) in both cultivars. For the gas produced between 3 and 20 h, representing the fermentation of cell walls in rumen fluid, a stronger correlation () was found with the S:G ratio than with the ADL content (). The relationship between ADL content or S:G ratio and 72‐h gas production, representing total organic matter degradation, was weaker than that with gas produced between 3 and 20 h.CONCLUSIONThe S:G ratio plays a more dominant role than ADL content in maize stem cell wall degradation. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Highlights
Forage maize is an important forage for high-yielding dairy cows in most areas of the world
There was no clear trend for a greater level of Neutral detergent fibre (NDF), Acid detergent fibre (ADF) and acid detergent lignin (ADL) in more mature tissue
The concentrations of NDF, ADF, and ADL and ADL:potentially rumen degradable fibre (pRDF) ratio were greater in Ambrosini than in Aastar except for the internode harvested on d 14
Summary
Forage maize is an important forage for high-yielding dairy cows in most areas of the world. Research over the past decades has mainly focused on improving yield and proportion of starch in forage maize in order to obtain a greater nutritional value and accommodate more to the nutritional needs of cattle.[1] This focus did not lead to greater and/or more rapid degradation of the non-starch fraction of the plant (mainly cell walls).[1] Research into the causes of differences in degradability of the cell walls may result in better and faster degradability of cell walls of maize stems. Increased cell wall degradation of forage maize by harvesting at earlier stages of maturity will decrease starch content and increase enteric methane production.[2] forage maize with a greater cell wall degradation at a similar growth stage will have a greater nutritional value, so lower costs, lower environmental emissions and a better performance of the animals. Different internodes from two contrasting maize cultivars (Ambrosini and Aastar) were harvested during the growing season
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