Effect of maize kernel endosperm type and maturity stage on ruminal in situ degradability and post-ruminal in vitro dry matter and starch digestibility

Abstract

ABSTRACT: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 semiflint 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 < 0.001). Ground dent maize grain showed lower mean particle size than did that of semiflint maize (1.76 vs 1.88 mm, respectively, P < 0.001). Effective starch degradability calculated for the medium outflow rate (6%/h) was 69.1% vs 65.3% (P < 0.01) for dent and semi-flint maize and 69.0% vs 65.4% (P < 0.01) for lower (1/2 milk line) and higher (3/4 milk line) maturity, respectively. Higher (P < 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 < 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.

Starch composition related to physical traits in maize kernel

“…A recent study showed that kernel vitreousness depends more on starch-protein interactions and starch granule size and shape than on the molecular properties of starch, such as those measured through amylose content (Kljak et al, 2018). Small differences in kernel texture could significantly influence ruminal in situ degradability and total tract in situ-in vitro dry matter and starch digestibility (Trináctý et al, 2016).…”

Determination of the optimal priming interval of rumen fluids used as inocula for the in vitro digestibility trials through radial enzyme diffusion method

“…In addition, the change in the activity of Amy was less pronounced in the fermentation fluids from LFC-and LTMR-fed cows, and this is consistent with a possible higher abundance of amylolytic bacteria in the initial inoculum. The subsequent dynamic of Amy can be attributable to the gradual decrease in the amount of rapidly degradable starch in the system, followed, at 48 h of fermentation, by the degradation of the most crystallised forms of starch (Trináctý et al 2016). On the basis of the least-square mean values, it seems that the maximum similarity was at 8 h, while the lower variability was measured at 24 h.…”