Effects of Micronization on the In situ and In vitro Digestion of Cereal Grains

Abstract

The effects of micronization on in situ and in vitro nutrient disappearances of wheat, barley and corn were investigated in a series of experiments. In Experiment 1, chemical composition and in situ dry matter disappearance (DMD) of six varieties of wheat were determined. In addition, an in vitro study was completed using ground micronized and unmicronized wheat (var. Kansas). In Experiment 2, three varieties of wheat (Kansas, Sceptre and Laura) and in Experiment 3, three cereal grains (wheat, barley and corn) were either micronized for 1 min to attain internal kernel temperatures of 90-100°C or not (controls), and DM, protein and starch disappearances were estimated. In Experiment 2, an in vitro study was also completed using ground micronized and unmicronized wheat (var. Kansas). Wheat samples varied with respect to crude protein (10.0-21.2%), starch (61.6-73.9%), NDF (8.5-11.8%), volume weight (753-842 g/L) and kernel hardness (0.0-32.0). Rate (p = 0.003) and extent (p = 0.001) of in situ DMD differed among wheat varieties. Correlations between in situ kinetics, and chemical and physical properties of wheat varieties showed that protein content was negatively correlated with the rate of disappearance (r 2 = -0.77). Micronization of all grains markedly reduced (p = 0.001) the rate and extent of DM, and protein disappearances as compared to control samples. Micronization increased (p<0.05) the digestion of starch in wheat. However, release of ammonia into the incubation medium was markedly reduced (p<0.05), suggesting that micronization increased the resistance of protein to microbial digestion. Disappearances of DM, protein and starch differed (p = 0.001) among cereal grains with wheat>barley>corn. Micronization reduced the rate of DM disappearance (p = 0.011) and slowly degradable protein fractions (p = 0.03), however, increased (p = 0.004) slowly degradable starch fractions of all three cereals. Examination of in situ samples by scanning electron microscopy confirmed that microbial colonization focused on starch granules in micronized grains, and that the protein matrix exhibited resistance to microbial colonization. These results suggest that micronization may be used to increase the ruminal escape value of protein in cereal grains, but may lead to increased starch digestion if grains are finely ground.

In situ starch and crude protein degradation in the rumen and in vitro gas production kinetics of wheat genotypes

“…() assumed that the protein matrix of maize grains has a substantial influence on ruminal ST degradation, and many studies have confirmed that maize types with a higher proportion of hard endosperm have a significantly lower in situ DM or ST degradation in the rumen than soft endosperm varieties (Philippeau and Michalet‐Doreau, ; Correa et al., ; Lopes et al., ). For wheat, McAllister and Sultana () found that increased kernel hardness decreased in situ DM degradation and the correlation between the rate of DM degradation and kernel hardness (greater numbers indicated softer kernels) was r 2 = 0.53. This is within the range as the correlation we report between TW and KD with EDCP8 and EDST8, which suggests that grains with a tighter structural arrangement show lower ED in the rumen.…”

“…Several in situ experiments have studied the ruminal degradation of wheat grain, either in comparison with other grain types or as influenced by different growing and/or processing methods (Arieli et al, 1995;Givens et al, 1997;Michalet-Doreau et al, 1997;Philippeau et al, 1999;Turgut et al, 2004;de Campeneere et al, 2006;Lund et al, 2008;Arroyo et al, 2009). To our knowledge, only three studies compared the in situ degradation of different wheat grain genotypes Swan et al, 2006;McAllister and Sultana, 2011), and only two studies investigated the gas production (GP) kinetics of a set of different genotypes of wheat grains (Lanzas et al, 2007;Pozd ı sek and Vaculov a, 2008). Furthermore, only Hindle et al (2005) compared in situ ST degradation and in vitro GP profiles of wheat grain (a single sample) and determined ruminal degradation in vivo.…”

Effects of grain source and monensin level on growth performance, carcass traits and fatty acid profile in feedlot beef steers

“…Both barley and wheat have rapid starch degradation, but wheat starch is fermented more rapidly in the rumen than starch from barley (McAllister and Sultana, 2011). This may explain the numerical higher abscessed liver for steers fed wheat (0.54) than steers fed barley grain (0.33).…”

“…An early study demonstrated that the impact of including HW and SW in the diet on the growth performance of finishing cattle is minimal; the ADG, G:F, and NEg were, respectively, 1.32 vs. 1.28 kg/d, 147 vs. 141 g/kg, and 6.32 vs. 6.15 MJ/kg, for feeding hard winter wheat vs. soft winter wheat (Brethour et al, 1985). Fail to observe the difference in growth performance of feedlot steers fed HW vs. SW is somewhat not expected as increased kernel hardness is associated with a decline in the rate of DM and starch disappearance in the rumen (McAllister and Sultana, 2011); variation in the rate of starch degradation in the rumen of high-grain diet with highly fermentable grain such as wheat grain would affect ruminal pH, consequently affect DMI and growth rate. However, Yang et al (2012) indicated that there is inconsistency between rumen fermentation characteristics measured in short period (e.g., 21 d) in a metabolism trial and growth performance measured in long period (120 d) in a growth trial.…”

Effect of High-Temperature Short-Time ‘Micronization’ of Grains on Product Quality and Cooking Characteristics

“…In another study, it was shown that micronization of wheat at temperatures of 90-100°C improved the feed efficiency in broilers, whereas the feed efficiency decreased when processed at temperatures of 120°C [37]. The effects of micronization on in situ and in vitro nutrient disappearances of wheat, barley and corn were investigated by McAllister and Sultana [29]. Micronization appeared to alter the nature of the protein matrix and slow the in situ rate of starch digestion in all varieties (Sceptre, Laura, Kansas) of wheat examined.…”