Low-density diets may improve welfare of restricted fed broiler breeders by increasing feed intake time with less frustration of feed intake behavior as a result. Moreover, low-density diets may promote satiety through a more filled gastrointestinal tract, and thus feelings of hunger may be reduced. Broiler breeders were fed 4 different diets during the rearing and laying periods. Behavioral and physiological parameters were measured at different ages as indicators of hunger and frustration of the feeding motivation. A diet of 8.4 MJ/kg as compared with a standard diet of 10.9 MJ/kg extended feeding time and reduced stereotypic object pecking at 6 and 10 wk of age. Furthermore, compensatory feed intake at 12 wk of age was reduced. During lay, differences in behavior were observed between the treatments that could be attributed to differences in feeding time. However, birds fed the diet with the lowest energy content (i.e., 9.2 MJ/kg) had higher heterophil to lymphocyte ratios (H/L) at 40 wk of age compared with the other treatments, indicating that they experienced more stress during the laying period than the other treatments. This result could have been due to the very long feeding time of this treatment group during lay, which may be stressful. In conclusion, a low-density diet of 8.4 MJ/kg may reduce hunger and frustration in the first half of the rearing period. However, for substantial improvement of broiler breeder welfare during rearing, more extreme diet modifications are required.

1. The effects of an indigestible soluble polysaccharide (carboxy methyl cellulose: CMC) on broiler performance (body weight gain, food and water intake) and on chyme characteristics (moisture content, viscosity, pH, osmolality and retention time) in broilers were studied. 2. In semi-synthetic diets 0, 5.0 and 10.0 g/kg of cellulose was replaced by CMC on weight basis. These diets were fed to male broilers from 3 to 5 weeks of age. 3. When 10.0 g/kg CMC was included in the diet, food intake and body weight gain were reduced, compared to the 0, and 5.0 g/kg CMC diets. Food:gain ratio and water intake were increased at each CMC concentration. The significant quadratic response showed an increased response per 5.0 g/kg dietary CMC at the higher CMC concentration. 4. The viscosity in the supernatant of the chyme was linearly increased in all intestinal segments by CMC. A quadratic increase was observed in the crop. In the lower ileum, differences between the 5.0 and 10.0 g/kg CMC diets were not significant. 5. CMC increased the mean retention time of chromium in the duodenum and in the upper jejunum, and reduced the maximal rate of marker excretion. The transit time (first appearance of the marker in the excreta), however, was significantly reduced at the highest CMC concentration. 6. The osmolality of the intestinal fluid decreased less as the chyme moved from the duodenum into the lower ileum, with increasing concentrations of CMC. 7. The ileal pH was reduced linearly by the CMC content of the diet. 8. Based on a higher moisture content of the chyme in the CMC-fed birds, and the higher jejunal and ileal osmolarities in those birds, it was concluded that the efficiency of both digestion and absorption was reduced by CMC inclusion in broiler diets.

Five-week-old broilers were used to estimate the retention time parameters of DM in the gastrointestinal (GI) tract. From 3 to 5 wk of age semisynthetic diets were fed with 0,1, and 2% carboxy methyl cellulose (CMC, an indigestible soluble polysaccharide). These diets were obtained by exchanging cellulose by CMC. The cumulative excretion curves of a marker (Cr)containing meal were fitted to the data at fecal and intestinal level, using a generalized logistic curve. The transit time (time of first appearance at site of measurement) was estimated as well as some retention time parameters (time of 50% excretion of the Cr intake; time at and rate of maximal Cr excretion).Addition of CMC decreased the transit time from mouth to feces by 60 min (0% CMC versus 2% CMC, respectively). The first differences in transit time were observed in the posterior part of the jejunum. In contrast to transit time, 2% CMC increased the time of 50% Cr excretion by 2 h. Furthermore, CMC reduced the maximal rate of marker excretion, suggesting a more intensive mixing between the Cr-containing meal and the rest of the chyme.Because the transit time was not related to shape of the excretion curves, the former should be used cautiously as an indication of the mean retention time in the GI tract. However, determination of a cumulative excretion curve at fecal level might also be erroneous, because marker entrance into the ceca may depend on dietary composition. (

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1. The effect of an indigestible soluble polysaccharide (carboxy methyl cellulose: CMC) on the absorption of some macro-elements (sodium, potassium, calcium, phosphorus and magnesium) from different segments of the small intestine of broilers was determined. 2. In semi-synthetic diets 0, 5.0 and 10 g/kg cellulose was replaced by CMC on weight basis. These diets were fed to male broilers from 3 to 5 weeks of age. 3. CMC inclusion reduced the rate of mineral absorption throughout the small intestine. The effect of CMC on sodium absorption was more pronounced than the effects on the absorption of the other minerals. 4. The cumulative absorption of all minerals up to the lower jejunum was reduced by dietary CMC. This negative effect of CMC on the absorption of minerals was alleviated in the lower ileum, except for potassium. 5. The concentrations of sodium and magnesium in the chyme supernatant were clearly decreased, while those of calcium and phosphorus were increased by dietary CMC inclusion. Taking the mineral concentrations in the total chyme into account, the solubilities of calcium, phosphorus and magnesium in the ileum were increased by dietary CMC. The solubilities of sodium and potassium were not increased. 6. The reduced cumulative absorption of minerals from the gastrointestinal tract with increasing dietary concentrations of CMC, was probably caused by the higher intraluminal viscosities in the small intestine. It is not likely that either the intestinal pH, or the time food was retained in successive gastrointestinal segments, will have affected mineral absorption negatively in any segment.