On the influence of diet on the retention time of food in the digestive tract of cows

The retention times of dry matter and its constituents in the digestive tract of cows on hay+sugar beet pulp (5 cows) and cows fed on hay+swedes (8 cows) are compared with the retention times pertaining to cows fed on hay+concentrate or hay only. The following conclusions were reached; On a hay+sugar beet pulp diet the mean retention time of dry matter in the reticulo-rumen, and the retention times of lignin in the reticulo-rumen, in the whole digestive tract, and in the digestive tract following the reticulo-rumen are of the same magnitude as the corresponding retention times on a hay+concentrate diet (figs. 1, 2, 5, and 6). The mean retention time of membrane substances in the reticulo-rumen seems to be shorter and that of valuable N-free nutrients in the reticulo-rumen longer than the corresponding retention times on a hay+concentrate diet (figs. 3 and 4). On a hay+swede diet the mean retention times of dry matter and membrane substances in the reticulo-rumen are of the same magnitude as on a hay+concentrate diet (figs. 1 and 3). The mean retention time of valuable N-free nutrients in the reticulo-rumen and, in abundant feeding, the retention times of lignin in the reticulo-rumen, in the whole digestive tract, and especially in the digestive tract following the reticulo-rumen are shorter than on the hay+concentrate diet (figs. 2, 4, 5, and 6). On the hay+sugar beet pulp and the hay+swede diets the retention times are in general of the same magnitude. However, the retention time of membrane substances in the reticulo-rumen is shorter and that of the valuable N-free nutrients considerably longer on a hay+sugar beet pulp than on a hay+swede diet. Replacing a certain amount of hay by concentrates, sugar beet pulp or swedes on a dry matter basis seems to have no effect on the mean retention time of dry matter in the reticulo-rumen. However, a retarding effect on the rate of passage of typical hay constituents (lignin and membrane substances) and an accelerating effect on that of valuable N-free nutrients characteristic of concentrated foods was observed. The said replacing accelerates the rate of passage of lignin in the disgestive tract following the reticulo-rumen on a hay+swede diet.