Between July 1990 and April 1991 the rate of contamination with Salmonella species of poultry feeds and feed components used by the Dutch feed industry was surveyed. Ten per cent of 360, 10 g samples of poultry feeds were found to be contaminated. Mash feeds, mostly used for layer-breeders, were far more frequently (21 per cent) contaminated than pelleted feeds (1.4 per cent). The rate of contamination of 130 samples of fish meal was 31 per cent, of 83 samples of meat and bone meal 4 per cent, 58 samples of tapioca 2 per cent and of 15 samples of maize grits 27 per cent. Twenty-eight serotypes of salmonellae were isolated, but no Salmonella enteritidis was found, despite the occurrence of an epidemic in poultry caused by this serotype since 1987. The serotypes isolated most frequently were not the same as those encountered in poultry flocks. The Enterobacteriaceae isolated from the feedstuffs were predominantly thermotrophic. They were shown to be useful markers of the rate of contamination with salmonellae and of the efficiency of decontamination of the feedstuffs by pelletisation.

In three experiments broiler chickens were inoculated with sporulated Eimeria acervulina oocysts at 18 d of age. Feed intake, body-weight gain, brush-border enzyme activities, fat digestion, protein digestion and protein retention were measured. Body-weight gain was reduced during the acute phase of the infection and increased during the recovery phase of the infection. Feed intake was decreased on day 4 and day 5 postinfection (PI) and increased from day 7 to day 11 PI. Maltase (EC 3.2.1.20) and sucrase (EC 3.2.1.48) activities were decreased on day 5 PI in all intestinal segments. In Expts 2 and 3, however, maltase activity was increased in the ileum. Fat digestion was decreased from day 2 to day 11 PI. N digestion and retention were decreased from day 2 to day 11 PI.

1. Experiments were conducted to measure the effect of xylanase supplementation on the performance of broilers fed on wheat-based diets containing high and low extract viscosity wheat (experiment 1), baking and feeding quality wheat (experiment 2) and with variation in wheat content (experiment 3). 2. Xylanase supplementation improved food conversion ratios by 2.2-2.9% and body weight gain by 0.2-2.5%. This was independent of wheat characteristics but slightly dependent on the wheat content of the diet. These effects were related to a lowering of digesta viscosity. 3. Differences in extract viscosity of wheat were not reflected in broiler digesta viscosity. 4. Reduction of digesta viscosity resulted in only a slight improvement of litter score. Reduced intestinal viscosity decreased relative pancreas weight and to a lesser extent relative small intestinal weight. 5. Baking quality wheat Baldus gave better performance than the feed quality wheats Apollo and Slejpner. 6. It was concluded that xylanase supplementation of wheat-based diets invariably had a positive effect on broiler performance.

Previously an experimental infection model was developed in which broiler chickens were inoculated with sporulated Eimeria acervufina oocysts at an age of 18 d. The infection resulted in adverse performance results and reduced nutrient digestion. In two new experiments with the infection model effects of diet adjustments on fat digestion were investigated. In the first experiment addition of 0.4 g cholic acidlkg to a diet rich in animal fat resulted in increased fat digestion during the infection. In the second experiment replacing animal fat by coconut oil resulted in improved fat digestion during the coccidiosis infection. However, replacement of animal fat by soyabean oil did not improve fat digestion. Poultry: Coccidiosis: Fat digestionIn a previous paper (Adams et al. 1996) an infection model was introduced in which chickens were inoculated with sporulated Eimeria acervulina oocysts. As Eimeria acervulina affects a specific region of the intestine, this infectious disease can be used as a model to study nutrition-infection relationships in order to adjust diet compositions during the acute and recovery phases of enteral infections.

1. An experiment was conducted with female broilers from 1 to 39 d of age in which the effects of increasing amounts of extra dietary ferrous sulphate on growth performance, some haematological measurements and Fe, Zn and Cu status were studied. A conventional maize-soyabean diet (107 mg Fe/kg) was supplemented with 0, 20, 60, 180, 540 and 1620 mg Fe to provide 6 treatments. 2. Weight gain responses rose to a plateau between 20 and 60 mg added Fe/kg diet, but further additions of Fe increasingly depressed growth. 3. In this study the apparent Fe requirement was 100 mg/kg diet (80 mg from dietary components and 20 mg Fe from supplement). 4. The efficiency of food utilisation decreased linearly, while the proportion of chicks affected by leg weakness increased. 5. In blood, the haemoglobin concentration increased slightly with extra dietary Fe. 6. The iron content of the liver increased with higher dietary Fe supplementation. Furthermore, increased liver Fe content was associated with a higher Zn content in the liver. 7. This study indicated that a maize-soyabean diet containing about 30% more Fe than has generally been accepted to be adequate for healthy broilers was still marginal in Fe concentration.