Six half-bred ½ Holstein-Zebu steers, fistulated in the rumen and abomasum, were randomly assigned to two 3 x3 Latin squares (animal, ingestion regime - 1.5, 2.0 and 2.5% LW and period) to determine the intake and total and partial digestibility of total carbohydrates (CHO), neutral detergent fiber (NDF) and non fiber carbohydrates (NFC). Chromic oxide was used as a marker to determine the digestibilities. Animals were fed diet with 60% Tifton-85 bermudagrass (Cynodon spp.) hay and 40% concentrate mixture (corn starch, wheat middling, soybean meal, urea and minerals), were used. Intakes CHO, NDF, NFC and TDN (kg/day, %LW) linearly increased with the ingestion regimes. The identity model test, used to estimate the regression equations for the total, ruminal and intestinal digestibilities of CHO, in function of the ingestion regime, showed no differences among collection methods. Total, ruminal and intestinal carbohydrates digestibilities were not affected by the treatments. Neutral detergent fiber total digestibility linearly decreased as the ingestion regime increased, while NDF ruminal and intestinal digestibilities were not affected by the treatments. No effect of ingestion regime was observed for the NFC total digestibilities. A linear increase of NFC ruminal digestibility was observed by using the omasal method of digesta collection. When the abomasal method of digesta collection was used, no effect of increased intake on the NFC ruminal digestibility was observed. Abomasal method of digesta collection could be replaced by omasal method of digesta collection, by ruminal fistula. Omasal method of Digesta collection is an efficient method, becoming the study of partial digestion a less invasive process.
omasum digesta collection; intake; digestibility; ingestion levels; steers
