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The effects of substituting corn with glycerol on DNA concentration of selected ruminal bacteria were investigated using continuous fermenters. Four continuous culture fermenters were used in a 4 × 4 Latin Square design with four 10 days consecutive periods. Treatment diets (60:40 forage to concentrate) were fed at 45 g/day dry matter (DM) in three equal portions. Glycerol (0.995 g/g glycerol) was used to replace corn in a grain mix at proportions of 0% (T0; control), 15% (T15), 30% (T30) and 45% (T45). On day 10 of each period, samples were collected from each fermenter 3 h after the morning feeding and analysed for volatile fatty acid and bacterial DNA concentration. Glycerol substitution was related to significantly higher butyrate, valerate and isovalerate concentrations. Compared with the T0 diet, acetate concentration was significantly lower with the T30 and T45 diets whilst propionate concentration was higher only with the T45 diet. The DNA concentrations for Butyrivibrio fibrisolvens and Selenomonas ruminantium decreased with the T30 and T45 diets compared with the T0 diet. No differences in the DNA concentrations for Ruminococcus albus and Succinivibrio dextrinosolvens amongst diets were observed. The findings show that substituting 15% of the dietary corn with glycerol had no substantive effects on fermentation processing or ruminal bacteria. Higher substitution levels, however, may adversely affect ruminal bacteria and negatively impact acetate production.

Key words: wheat flour, whole meal barley, gelatinized corn flour, balady bread, chemical parameters, rheology, quality This study was focused on substituting a part of wheat flour (WF) with whole meal barley (WBF), gelatinized corn flour (GCF) and both of them in balady bread, as an attempt to solve the shortage in wheat production. Chemical, rheological, color and sensory properties were determined. Stalling of balady bread was evaluated. It is found that the incorporation of WBF and GCF into balady bread improved protein, fat, fiber, ash, β-glucan and minerals (Ca, P, K and Fe). Blending WBF or GCF with WF gave higher rheological parameters of dough; meanwhile lightness of the produced breads was reduced. Also, sensory properties of the separation layers and roundness were not affected significantly, but a significant difference was observed in taste, crust colour and odour at replacement level of 30%. Generally, WF supplemented with WBF:GCF (30:15%) did not affected technological quality of balady bread and improved its nutritive values.

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