FURTHER QUANTITATIVE DATA ON THE ROLE OF THE RUM INANT PROVENTRICULI IN THE DIGESTION AND ABSORPTION OF NITROGEN-FREE ORGANIC MATTER L. Paloheimo and A. Mäkelä Department of Animal Husbandry, University of Helsinki Received August 4, 1960 In an earlier paper Paloheimo et ai. (5, p. 70) have described a method for obtaining quantitative data on the role of the proventriculi (reticulo-rumen and omasum) in the digestion of nitrogen-free organic matter. In their experiments on 14 cows and 5 young bulls it appeared that of the total amount of the N-free non-lignin organic matter digested in the whole digestive tract 76—99 % disap- peared in the proventriculi. When the results for two of the cows were discarded the limits in the cows were 85 and 91 %. In those experiments the animals were fed with hay only. In the said paper earlier investigations on the subject are reviewed. Of later investigations those of Balch (1, p. 213) and Hogan (2, p. 25P) deserve to be mentioned. In the experiments of Balch made with fistulated cows which were fed on a variety of rations, small samples of the digesta lying in the region of the reticulo-omasal orifice were taken at frequent intervals over several days and combined to form a sample regarded as representative of the material passing to the omasum. The lignin-ratio technique was applied to values for the constituents of this sample in combination with values for the weight of the corresponding constituents in the food and of lignin in the faeces. It appeared that of the total dry matter disappearing from the alimentary tract from 43 to 83 % disappeared in the reticulum and rumen. The values for animals receiving a high proportion of concentrates in the ration are at the upper end of the range. In the experiments of Hogan with sheep the flow of digesta in the duodenum was exteriorized so that the digesta flowing from the stomach could be measured and sampled, and then returned to the duodenum. It appeared that almost 70 % of the digestible dry matter of the ration consisting of hay and a concentrate mixture was lost between the mouth and the duodenum. 220 Experimental As in the earlier investigation of the writers, the digestibility in the proventri- culi was determined using the lignin-ratio technique. Analyses were made of the food and of the contents in the abomasum. The cows used in these experiments were the same which had been the experimental animals in the experiments for determining the rate of passage of food in the digestive tract (6, p. 1; 4, p. 39). In those experiments it was necessary to kill the animals at the end of the experi- mental feeding. Before this the digestibility in the whole digestive tract had been determined applying the lignin-ratio technique. In determining the digestibility in the proventriculi the contents of the abomasum were considered as excrement of the proventriculi. As the endogenous nitrogen containing substances impede the determination of the true digestibility of nitrogenous substance of the food the digestibility percentages were calculated only for N-free organic matter and N-free non-lignin organic matter. As in the earlier investigation, the experimental cows were of Ayrshire breed. Four of them received hay as their only food. 17 were fed with hay and concentrates (chiefly maize) in a ratio of 1: 0.5, and 4 with hay and concentrates in a ratio of 1:1. Five of the cows received hay and beet pulp in the dry matter ratio of 1:0.5, and 8 hay and swedes in the dry matter ratio of 1:0.5. The hay used was timothy harvested at the beginning of blooming. Further notes concerning the feeding of the cows are given in the above mentioned papers of Paloheimo and Mäkelä. Results and discussion The results of the experiments are given in Table 1. The consumption of food is given in kg dry matter per 100 kg reduced net weight. This is obtained by sub- tracting the amount of contents in the alimentary canal from the live weight and reducing the obtained net weight to a normal state with regard to its degree of fatness (3, p. 66). In the Table the animals in each group are enumerated according to the relative consumption of dry matter, beginning from those whose consumption per 100 kg reduced net weight was the smallest. It is evident that the individual results obtained with this method are some- times misleading. Especially the smallness of the samples obtained from the abo- masum can lead to errors. The table shows, however, that the share of the pro- ventriculi in the digestion of the N-free non-lignin organic matter must be rather large irrespective of the composition of the ration. As for the results obtained with different feedings one sees that in the first group the digestibility in the whole digestive canal has been greater than in our earlier experiments, whereas the digesti- bility in the proventriculi has been of the same order as earlier. Thus the ratio a:b, i.e. the relative share of the proventriculi, is smaller. Probably the result in the case of cow 27 is erroneous. Similarly it is probable that in the 2nd group the cows 29, 32, and 41 have given erroneous results. Apart from these the ratio a:b varies in 14 cows of group 2 between 0.58 and 0.85. Omitting also the two highest 221 Table 1. The digestibility of nitrogen-free non-lignin organic matter in the proventriculi and in the whole digestive tract of cows. Digestibility of Digestibility of Food dry- N-free non-lignin Food dry- N-free non-lignin matter kg organic matter matter kg organic matter CoW kTredu- a) in pr°‘ b) in the a;b 9?W ksredu- a) “* ?r°' b) the a;bNo. ventriculi whole No. & ventriculi wholeced net 0/ disestive ced net