Studies on the process of digestion in the fowl: Dry matter and total nitrogen

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Abstract
Four pelleted diets, based on soybean meal (N = 4.40%), fish meal (N = 2.41%), field bean (Vicia faba L.) meal (N = 2.05%) and maize dextrin (N = 0.10%), were each offered to sixteen 13‐week‐old pullets for a 2 h period. Four birds from each group were killed 2, 4, 6 and 8 h after the feeding period and samples of the ingesta were removed from the gastro‐intestinal tract. The same experimental procedure, using the soybean meal diet, was also applied to sixteen 17‐week‐old and sixteen 24‐week‐old pullets. Nitrogen and chromium sesquioxide were determined on the freeze‐dried ingesta removed from the crops, proventriculi and gizzards, duodena, jejuna, ilea, caeca and large intestines of all the groups. The results indicated that the crop, proventriculus and gizzard acted as food reservoirs, that passage of food through the duodenum was very rapid and that the amount of the ingesta in the caeca depended on the diet, and was possibly affected by the nature of the carbohydrate. The rate and mode of digestion of the dietary protein was not dependent on time after the meal nor on bird age. Differences appeared to exist in the digestion of the different diets, particularly with respect to the amount of endogenous nitrogen present in the duodenal ingesta. These differences could not be explained in terms of the nitrogen contents of the diets, but may have been the result of the extrusion procedure when the texture of the diets and, hence, ingesta were important factors. The nitrogen values of the duodenal contents from the birds given the fish meal diet indicated a two‐fold increase over that of the food, whereas the corresponding values for those from the birds given the soybean meal and field bean meal were five‐ and fifteen‐fold respectively.