Effect of maize kernel endosperm type and maturity stage on ruminal in situ degradability and post-ruminal in vitro dry matter and starch digestibility
2016
Trinacty J, Nedelnik J, Lang J et al.
The objective of this study was to evaluate the interaction effect of maize grain texture (dent vs semi-flint) and two different stages of maturity (1/2 vs 3/4 milk line) on ruminal starch degradability and total tract digestibility using in situ and combined in situ–in vitro methods, respectively. The content of whole plant dry matter was 324.6 vs 399.5 g/kg (1/2 vs 3/4 milk line, respectively) for dent maize and 330.2 vs 401.3 g/kg for semi-flint maize. Organic nutrients (neutral detergent fibre, crude protein, ether extract, starch), 1000-grain weight, vitreousness, and mean particle size were determined. The evaluation was performed using two non-lactating Holstein cows fitted with ruminal cannulae. Effective degradability of dry matter and starch was calculated at ruminal outflow rates of 4, 6, and 8%/h. Vitreousness was lower for dent than for semi-flint grain, averaging 65.6% and 74.3% (P less than 0.001). Ground dent maize grain showed lower mean particle size than did that of semi-flint maize (1.76 vs 1.88 mm, respectively, P lerss than 0.001). Effective starch degradability calculated for the medium outflow rate (6%/h) was 69.1% vs 65.3% (P less than 0.01) for dent and semi-flint maize and 69.0% vs 65.4% (P less than 0.01) for lower (1/2 milk line) and higher (3/4 milk line) maturity, respectively. Higher (P less than 0.001) mean starch total tract digestibility was found for dent maize (88.5%) than for semi-flint maize (82.5%) and for kernels harvested at 1/2 milk line (87.4%) than for those harvested at 3/4 milk line (83.6%, P less than 0.001). Small differences in grain texture and silage maturity stage significantly influenced ruminal in situ degradability and total tract in situ–in vitro dry matter and starch digestibility.
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