Six castrated steers fistulated in the rumen and abomasum were randomly assigned to two 3 x3 Latin squares (three animals, three intake levels [1.5 supply, 2.0 and 2.5% LW] and three periods) to compare the collection techniques for abomasal and omasal digesta in order to determine the flow as well as to evaluate the effects of the three offer levels (1.5; 2.0 and 2.5% live weight) on both intakes and total and partial apparent digestibilities of DM, OM, CP, EE and TDN. The chromic oxide was used to estimate the digesta flows and the fecal excretion. DM, OM, CP, EE and TDN intakes showed an increasing linear behavior, according to the ingestion levels. DM total apparent digestibility coefficient decreased linearly, as ingestion levels increased. DM apparent digestibility in the rumen did not differ among treatments and averaged 73.2% for the overall equations. OM total digestibility showed decreasing linear behavior, according to the ingestion levels, whereas the ruminal and total intestinal digestibilities were not affected by the treatments (average of 81.6 and 18.4% for the overall equations, respectively). The model identity test showed some differences among the CP total digestibilities obtained by different methodologies were observed. When ruminal and intestinal digestions were compared, no differences among both methodologies were observed. EE total digestibility was not affected by the treatments, with average value of 76.3%. EE total ruminal and intestinal digestibilities exhibited both increasing and decreasing linear behaviors, respectively, as a function of the ingestion levels, showing an average value of 76.3%. EE total ruminal and intestinal digestibilities showed both increasing and decreasing linear behaviors, respectively, as a function of the ingestion levels. Omasal digesta collection, through ruminal fistula, can be used to replace abomasum fistula, becoming the study of digestion locals a less invasive process. TDN content decreased as feed offer levels increased.
steers; ingestion; digestibility; omasal digesta collection; abomasal digesta collection
