Level of Feed Intake and Site and Extent of Digestion of High Concentrate Diets by Steers

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Abstract
Crossbred steers (285 kg), fitted with permanent rumen cannulae and fed an 84% corn diet at 1.00, 1.33, 1.67 and 2.00 times maintenance (M) intake (LOOM, 1.33M, 1.67M and 2.00M, respectively), were employed in a 4 × 4 Latin square design. Site and extent of dry matter, organic matter and starch digestion were estimated by withdrawing rumen samples and assuming such samples would be equivalent to abomasal samples if a constant flow of digesta was maintained by frequent feeding. Permanganate lignin was used as a marker. Ruminal digestion coefficients were calculated on the basis of a lignin in feed to lignin in rumen digesta ratio. Total tract dry matter digestion (DMD) was lower (P<.05) for 2.00M (77.6%) and 1.67M (78.9%) than for 1.33M (84.1%) and LOOM (85.7%). Ruminal DMD declined from 66.2% (LOOM) to 60.1% (2.00M) as intake doubled, with ruminal organic matter digestion (OMD) following a similar pattern. A trend for less dry matter and organic matter digested intestinally was observed as intake increased from LOOM (19.5%) to 2.00M (17.5%). Total tract starch digestion was greater (P<.05) for steers fed LOOM (99.6%) than those fed 1.67M (93.8%) and 2.00M (90.4%). Moreover, less starch (P<.05) was digested ruminally as intake increased from LOOM (94.5%) to 2.00M (89.6%). Rumen liquid volume decreased as intake increased from 1.00 M (23.6 liters) to 2.00M (18.6 liters), and liquid dilution rate and out-flow rate increased with increasing intake. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.