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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 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 ( = -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 (pbarley>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.

The objective of this study was to investigate the effect of dietary supplementation with calcium salts of soybean oil fatty acids (CaSO) and linseed oil fatty acids (CaLO) on c9,tl 1-CLA production in ruminal fluid and milk fat from Holstein dairy cows. Rumen fermentation, lactational performances and fatty acid profiles in ruminal fluid and milk fat were also investigated. Twenty multiparous Holstein dairy cows were allotted randomly into two groups consisting often cows in each group according to calving date and average milk yield. The first group of cows was fed a control (without calcium salts) diet and a treatment as 1.0% of CaSO (on DM basis) for 30 days in each period. In the second group, cows were fed the same control diet and 1.0% of CaLO as a treatment in the same manner. The forage: concentrate ratio was 52:48, and diets were formulated to contain 17% crude protein (DM basis) for both groups. Ruminal pH, protozoal numbers and the concentration of total volatile fatty acids were unchanged, however, the ruminal ammonia-N decreased by feeding CaSO or CaLO treatment compared to the control diet. The vaccenic acid (trans-11 C18:1; VA) in rumen fluid increased (p