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1. This study determined the effects of three protein sources (PS), each at two digestibility crude protein (DCP) levels, on performance, gut morphology and fermentation characteristics in the hindgut of broilers. 2. It was hypothesised that broilers fed ingredients high in indigestible CP, i.e. rapeseed meal (RSM) or maize gluten (MG), could potentially cause reduced growth, impaired gut health, and more protein fermentation products in caecal digesta. Increasing the DCP level in each of the indigestible CP diets may compensate for these detrimental effects. 3. In total, 288 one-d-old male Ross 308 broilers were used in a completely randomised 3 × 2 factorial design, with six replicate pens per treatment. Three PS: soybean meal (SBM), rapeseed meal (RSM) or maize gluten (MG), and two DCP levels: 15.8 and 17.2% were used. 4. Broilers fed SBM had increased feed intake and BWG and improved FCR compared with those fed RSM and MG diets. Broilers fed high DCP had better performance compared with those on low DCP. No significant effects of PS or DCP level were found on gastrointestinal tract development, caecal ammonia or volatile fatty acid concentrations. 5. Broilers fed SBM had longer villi, smaller crypts and increased villus height to crypt depth ratio compared with those fed RSM and MG diets. Broilers fed RSM diet had a lower caecal pH, and had 16.5% and 14.9% more branched chain fatty acid contents in caecal digesta compared with those fed SBM and MG diets, respectively, indicating more proteolytic fermentation. 6. Replacing SBM by RSM and MG negatively affected growth performance and gut morphology. Hindgut protein fermentation was substantially increased in RSM fed birds. 7. To a certain extent, retarded growth performance in RSM and MG fed birds could be counterbalanced by increasing the dietary level of digestible CP.

1. In poultry investigations, the main interest is often to study the effects of many factors simultaneously. Two or three level factorial designs are the most commonly used for this type of investigation. However, it is often too costly to perform when number of factors increase. So a fractional factorial design, which is a subset or a fraction of a full factorial design, is an alternative. The Taguchi method has been proposed for simplifying and standardising fractional factorial designs. 2. An experiment was conducted to evaluate the applicability of the Taguchi method to optimise in vitro intrinsic phytase activity (IPA) of rye, wheat and barley under different culture conditions. 3. In order to have a solid base for judging the suitability of the Taguchi method, the results of the Taguchi method were compared with those of an experiment that was conducted as a 34 full factorial arrangement with three feed ingredients (rye, wheat and barley), three temperatures (20 degrees C, 38 degrees C and 55 degrees C), three pH values (3.0, 5.5 and 8.0) and three incubation times (30, 60 and 120 min), with two replicates per treatment. 4. After data collection, a Taguchi L 9 (3(4)) orthogonal array was used to estimate the effects of different factors on the IPA, based on a subset of only 9 instead of 81 treatments. The data were analysed with both Taguchi and full factorial methods and the main effects and the optimal combinations of these 4 factors were obtained for each method. 5. The results indicated that according to both the full factorial experimental design and the Taguchi method, the optimal culture conditions were obtained with the following combination: rye, pH = 3, temperature = 20 degrees C and time of incubation = 30 min. The comparison between the Taguchi and full factorial results showed that the Taguchi method is a sufficient and resource saving alternative to the full factorial design in poultry science.

1. The objective of this experiment was to study the influences of xylanase and citric acid on the performance, nutrient digestibility, digesta viscosity, duodenal histology, and gut microflora of broilers fed on a wheat based diet. 2. The experiment was carried out as a 2 × 3 factorial arrangement with two concentrations of xylanase (0 and 200 mg/kg) and three concentrations of citric acid (0, 20 and 40 g/kg). A total of 408 one-day-old chickens with similar body weight were distributed into 24 pens with 17 birds/pen. Each dietary treatment was given to 4 replicate pens from 0 to 24 d of age. To determine the apparent nutrient digestibility, chromic oxide (3 g/kg) was added to the diets as an indigestible marker. 3. Xylanase significantly increased body weight gain at 24 d of age by 1·4% and improved gain-to-feed (G:F) by 3·6%. The inclusion of 40 g/kg citric acid decreased feed intake and body weight gain by 15·4% and 11·8%, respectively. The inclusion of 20 g/kg of citric acid decreased feed intake, but it did not affect body weight gain of broilers at 24 d of age. The inclusion of 20 and 40 g/kg citric acid improved G:F by 3·8 and 4·3% respectively. Xylanase significantly decreased the viscosity of digesta and improved retention of DM, CP, and energy. 4. Xylanase and citric acid did not have any effect on the histo-morphology of the duodenum and intestinal microbial population. 5. In conclusion, citric acid at 20 g/kg decreased feed intake, did not have a negative effect on body weight gain, and improved G:F. Xylanase decreased digesta viscosity, increased nutrient retention and consequently improved performance of broilers fed on a wheat based diet.

1. From an experiment with 504 laying hens (ISA Brown strain, 18-40 weeks of age), 90 40-week old hens were used for determining digesta mean retention time (MRT) and gut weight development. This experiment comprised 6 dietary treatments according to a 2 × 3 factorial design. Factors were dietary apparent metabolisable energy (AME) concentration (11·8 vs 10·6 MJ/kg), insoluble nonstarch polysaccharides (NSP) concentration (65 vs 134 g/kg), and fine vs coarse particle sizes of added NSP. Titanium recovery in different gut segments was used as an indicator of MRT. 2. Increasing NSP concentration prolonged MRT in the crop (68 vs 34 min) and total foregut (91 vs 57 min) compared with control NSP. Reducing energy concentration prolonged MRT in the colon (26 vs 7 min), and total hind gut (30 vs 9 min), compared with control energy. Overall MRT was not affected by dietary treatments. 3. Increasing NSP concentration increased relative weights of the empty proventriculus-gizzard and its contents by 30% (25·2 vs 19·4 g/kg) and 18% (15·4 vs 13·0 g/kg), respectively, compared with control NSP diets. 4. MRT in the foregut was prolonged as daily insoluble NSP intake increased, and this was more pronounced in hens given coarsely ground NSP, compared with finely ground. A prolonged MRT in the foregut seemed to indicate a higher level of satiety, which may contribute to a lower feather pecking pressure in laying hens.