The genetic parameters of digestibilities for a wheat-based diet were estimated on 864 broilers. Two divergent lines (D+ and D-) were developed based on AMEn. The Rialto wheat variety was used as it is known to result in low digestibility values. Digestibility of lipids (DL), starch (DS), and proteins (DP) were measured individually using Near Infrared (NIR) analysis of freeze-dried excreta. Body weight, feed consumption (FC), feed conversion ratio (FCR) and residual feed consumption (RES) were recorded to evaluate their correlation with AMEn. The mean AMEn value was 3,093 kcal/kg DM (CV = 9.0%), with a range of 1,001 to 4,022 kcal/kg DM, and was highly heritable (0.36 to 0.38) based on the Restricted Maximum Likelihood method. Genetic correlations with BW were low (-0.10 to -0.15). Selection for AMEn can thus be performed without modifying BW. In contrast, the estimated genetic correlations between AMEn and the other traits were highly negative (-0.53 to -0.60 for FC, -0.77 to -0.80 for RES, and -0.77 to -0.84 for FCR). Finally, digestibilities of feed components were moderately to highly heritable (0.33 to 0.47) and highly correlated with AMEn (0.91 for DL, 0.83 for DS, and 0.86 for DP). Selecting for improved AMEn should thus improve digestibility of proteins, starch, and lipids. The first generation of divergent selection on AMEn confirmed these results, D+ and D- lines showing a 13% difference in AMEn (P < 0.0001) and similar BW.

1. The aim of the experiment was to establish relationships between chemical or physical characteristics of wheats (Triticum aestivum) and digestibilities of food components in broiler chickens fed on wheat-based diets. Twenty-two wheat samples, each differing by their cultivar origin, were included at 550 g/kg in diets offered to male Ross broiler chicks. The other main ingredients were soya bean meal (340 g/kg) and rapeseed oil (68.5 g/kg). Diets were given as pellets. 2. In vitro viscosities of wheats measured as potential applied viscosity (PAV) or real applied viscosity (RAV) varied between 1.91 and 6.03, or between 0.95 and 3.81 ml/g (dry matter basis), respectively. Hardness of wheats varied between 17 (soft) and 95 (very hard), and lipase activity of wheats varied from 1 to 13.6 (relative scale). 3. PAV and RAV values were not significantly correlated with hardness. PAV and RAV values were correlated with (80:20) ethanol:water insoluble, water soluble arabinoxylans (r = 0.961, 0.932, respectively), with the amount of water retained by cell walls (r = 0.656, 0.492, respectively), and with lipase activity (r = 0.600, 0.532, respectively. 4. Hardness was correlated with ash (r = -0.484), nitrogen (r = 0.534), mean particle size of wheat flours (r = 0.631), and specific energy of pelleting (r = -0.574). 5. Wheat diets were evaluated in two assays with 3-week-old chicks, with 11 diets per assay. In each assay, a balance experiment was carried out using the total collection method. Growth performance was also measured during the balance experiment. 6. In vitro viscosity parameters were negatively correlated with diet AMEn (P < 0.05), lipid digestibility (P < 0.05) and, to a lesser extent, protein digestibility (P < 0.05). In vitro viscosity data were positively correlated with food:gain ratio (P < 0.05) and water loss parameters (P < 0.05), and were not significantly (P > 0.05) correlated with starch digestibility. 7. Wheat hardness-related parameters were correlated (P < 0.01) with individual starch digestibility (hardness, proportion of coarse particles in wheat flour, specific energy of pelleting: r = -0.273, -0.305, 0.212, respectively). 8. Wheat lipase activity was negatively correlated with individual lipid (r = -0.179; P < 0.05) and starch (r = -0.225; P < 0.01) digestibilities and with individual diet AMEn (r = -0.266; P < 0.001). Individual diet AMEn values were correlated (r = 0.175) with the values calculated by the EU AMEn prediction equation (Fisher and McNab, 1987). Among the correlations observed between the individual measured AMEn:EU predicted AMEn ratio and wheat parameters (P < 0.05), the correlation obtained with wheat lipase was the highest (r = -0.195). The correlations with lipase could be explained in part by strong correlations between lipase and in vitro viscosity parameters.

The aim of the present study was to reexamine the effects of intestinal viscosity, microflora, and bile salts, and their interactions in order to clarify the mechanisms that explain the effect of intestinal viscosity on lipid digestibility, especially those that could involve microflora. Effects of intestinal viscosity, microflora status, and dietary bile salts on lipid digestibility, intestinal bile salts, and intestinal histomorphology were tested in a 2 x 2 x 2 factorial experiment. The effect of microflora status was examined by comparing conventional chickens to chickens with limited microflora obtained by rearing birds in sterilized conditions. Viscosity and dietary bile salts were tested with guar gum (0 or 0.5% in diets) and sodium taurocholate (0 or 0.3% in diets), respectively. Guar gum was autoclaved and added to the gamma-irradiated diets by mixing inside the sterile isolators. The intestinal concentration of lactic acid and cecal concentration of short-chain fatty acids were both very low in birds with limited microflora compared to conventional birds (P = 0.0001). Chickens with limited microflora had higher gain:feed ratios (P = 0.002), higher fecal lipid digestibility (P = 0.0001), more intestinal conjugated bile salts (P = 0.0001), less intestinal unconjugated bile salts (P = 0.0001), and their gastrointestinal compartments were smaller (P < 0.05) than those of conventional chickens. Addition of bile salts in diets increased the lipid digestibility (P = 0.0001) with a more pronounced effect in conventional birds (P = 0.0001) and in birds fed on guar gum diets (P = 0.002). Feeding the guar gum diets increased the intestinal supernatant viscosity (P = 0.0001) for both microflora status. Guar gum addition increased (P < 0.05) the lactic acid concentration in the small intestine of conventional chickens. Guar gum decreased the fecal lipid digestibility (P = 0.0001) and the intestinal conjugated bile salts (P = 0.0001) for both microflora status. However, the magnitude of lipid digestibility decrease due to guar gum was lower (P = 0.05) in birds with limited microflora than in conventional birds, and the negative effect of guar gum on intestinal conjugated bile salts was more pronounced (P = 0.02) in birds with limited microflora. Bile salt addition reduced the negative effect of guar gum on lipid digestibility (P = 0.02) for both microflora status. The mean lipid digestibilities were negatively correlated (P = 0.0001) with the ratio [Ln(viscosity)/total bile salt] measured in intestinal digesta. Except for gizzard, size of digestive compartments and villus heights increased (P < 0.05) with feed efficiency and digestibility decreased. In conclusion, the results provided evidences that the negative effect of guar gum on lipid digestibility was mainly mediated by its direct effect on intestinal bile salt concentration and efficiency. The small interaction between guar gum and microflora status effects on lipid digestibility had to be accounted for by the low basal level of intestinal bile salts in conven...

The aim of this experiment was to compare the D(+) and D(-) chicken lines genetically selected for divergent digestion efficiency by testing the effects of diet particle size on growth performances, digestion efficiencies, and digestive organ weights in both lines. A 2 x 3 factorial arrangement of treatments was used to test the D(+) and D(-) lines (sixth generation) and 3 diets, namely a pelleted standard corn diet (S), a pelleted hull diet (H) made by diluting S diet with 7% coarse cereal hulls, and a coarse corn diet (C) identical to the S diet, distributed as 30% coarsely crushed corn mixed with the 70% pelleted remaining part. Experimental diets were fed from 7 to 26 d of age. Combining results from all diets obtained at 26 d of age, D(+) birds showed 9% heavier (P < 0.0001) gizzard and 10% lighter (P < 0.0001) small intestine than D(-) birds. The AME(n) and digestibilities of lipids, protein, and starch measured at 3 wk of age were, on average, 3.5, 5.6, 5.8, and 0.5% higher (P < 0.0002) in D(+) than in D(-) birds, respectively. Significant (P

The aim of the experiment was to study the effects of 2 wheat cultivars (Baltimor and Scipion) with different hardness values (75 and 5, respectively) on 2 divergent lines (D+ and D-) of broiler chickens selected on the basis of their digestion ability assessed by AME(n). Wheat was incorporated at 54.6% in diets. The other main ingredients were soybean meal (35.3%) and rapeseed oil (5.5%). Diets were given as pellets from 7 to 26 d. The experimental design was a 2 x 2 factorial design testing 2 wheat cultivars (soft or hard) on 2 selected lines of broiler chickens (high AME(n) or low AME(n)). From 7 to 16 d, D+ line showed lower (P < 0.0001) feed intake and feed:gain ratio than the D- line. At 3 wk of age, the D+ chickens resulted in increased digestibility values (P < 0.01) and 9% increased AME(n) value (P < 0.0001) compared with D-. Wheat cultivar effects on feed efficiency and AME(n) differed between lines. In the D+ line, their values were about 6% higher (P < 0.05) with soft than with hard wheat, whereas they did not differ in the D- line. However, wheat cultivar effect on starch digestibility did not differ between lines; soft instead of hard wheat resulted in about 6% improvement (P < 0.0001) in both lines. In the D- line, soft instead of hard wheat tended to reduce lipid and protein digestibilities, which explained why the starch digestibility improvement due to soft wheat was not converted into a significant AME(n) improvement in D birds. Study of digestive organ size revealed that increased proventriculus and gizzard weight (P < 0.05) could be one of the causes for the better digestion capacity of the D+ line. The pancreas was bigger (P < 0.01) in D- than in D+ birds, which probably came from an adaptation to a digestive disorder in D- birds.

The first aim of the experiment was to study the effect of wheat (Triticum aestivum) particle size on the digestibility of starch in a pelleted diet given to broilers. The second aim was to study the consequences of food deprivation before the excreta collection period (from 21 to 24 d). Wheat from a strong hardness cultivar was incorporated at 546.1 g/kg in diets. The other main ingredients were soybean meal (353.5 g/kg) and rapeseed oil (55.0 g/kg). Diets were given as pellets. The experimental design was a 2 x 2 factorial design testing two particle sizes of wheat flour and two procedures of a balance experiment (with or without food deprivation). Birds given diet C (wheat coarse grinding before pelleting) had significantly greater gizzard weight than birds fed on diet F (wheat fine grinding before pelleting). Starch digestibility value was significantly increased when birds were fed on diet F. This effect was halved by food deprivation. No significant effect of grain particle size was observed for protein and lipid digestibility values. However, food deprivation decreased apparent protein digestibility, with an effect which was more pronounced for fine than for coarse grinding. AMEN of the diet was significantly improved by fine grinding of wheat and decreased by food deprivation. However, no significant differences in growth performance were induced by differences in wheat grinding. No significant effect of grinding was observed on the water excretion:feed intake ratio. No significant difference was observed for vent score between treatments. There was over-excretion of starch in the first hours of refeeding following food deprivation.

1. Three maize diets containing 0, 1 or 3 g of guar gum per kg and 2 wheat diets were given to male broiler chickens for measurements of growth performance and nutrient digestibility. 2. The intestinal viscosities found with wheat diets were within the range of those observed with the 3 maize diets. The correlations between in vivo and in vitro viscosities were higher with real than with potential applied viscosity. 3. The gain:food ratio decreased (P < 0.05) with the addition of 3 g guar gum/kg. The mean gain:food ratio observed for wheat diets was lower (P = 0.007) than the mean value found for the 3 maize diets. 4. The negative effects of increased intestinal viscosity due to guar gum addition on nutrient digestibility were highest for lipids and lowest for starch. 5. Wheat diets resulted in much lower (P < 0.001) starch apparent digestibility compared to maize diets with added guar gum despite similar mean intestinal viscosities in the 2 groups of diets. Apparent lipid digestibility with wheat diets was lower (P < 0.01) than the value predicted from intestinal viscosity, the predictive model having been calculated with the guar gum added maize diets. Apparent protein digestibility did not differ between wheat diets and guar gum added maize diets. 6. It was concluded that the low apparent digestibilities of starch and lipid observed with wheats could not be attributed only to intestinal viscosity and that other factors appear to be implicated in the low digestibilities observed with the wheat samples tested in the present experiment.

The experiment consisted of a 2 3 2 3 2 factorial design testing the two D1 and D2 chicken lines selected for divergent digestion efficiency (fifth selection generation), xylanase (with or without) and ampicillin and collistin (with or without) supplementations. From 8 to 22 days, 144 chickens (18 birds per treatment) were fed a diet containing 55% wheat from a high-viscosity cultivar (Rialto). Effects of treatments were evaluated on individual growth performance (8 to 19 days), digestibilities of lipids and dry matter, dietary energy value (apparent metabolisable energy corrected to zero-nitrogen retention (AME n )), digestive organ and breast sizes, and intestinal bile acids at 3 weeks of age. Individual variabilities were much lower in D1 than in D2 birds for feed : gain ratios, digestibilities and AME n values. In all cases, feed : gain ratios were lower in the D1 than in the D2 line (P , 0.001), and D1 birds showed 22% to 86% higher values than in D2 birds (P , 0.001) for digestibilities and AME n . In D2 birds, antibiotics but not xylanase supplementation had significant effects on lipid digestibility (P , 0.01) and AME n (P , 0.05), whereas both supplements improved these parameters in D1 birds (P , 0.001 for both additives on lipids digestibility, P , 0.05 for xylanase and P , 0.01 for antibiotics on AME n ). Relative weights of gizzard and proventriculus, and gizzard : intestine weight ratio were higher in D1 than in D2 birds, while relative weight of intestine was increased in D2 birds compared with D1 birds. Antibiotics reduced intestine relative weight in D1 (P , 0.001) and D2 (P , 0.01) lines. AME n variations were efficiently predicted by the gizzard : intestine weight ratio. In conclusion, antibiotics were very efficient for improving growth performance, AME n and digestibility values in both chicken lines. Xylanase was less efficient than antibiotics. Because of their low individual variabilities, D1 birds were much more efficient than D2 ones for the detection of significant effects induced by xylanase supplementation. Differences between lines in feed : gain ratio, digestibilities and AME n were reduced when xylanase and antibiotics were added together. Effects of xylanase supplementation and animal genetics on lipid digestibility could not be entirely explained in terms of intestinal bile acids. Other factors should be involved, especially for the lipid digestibility difference induced by animal genetics. The gizzard : intestine weight ratio was an efficient parameter for predicting AME n variations due to animal genetics and additives.