Influence of Forage Level on Passage Rate, Digestibility and Performance of Cattle

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Abstract
Two trials (feedlot and metabolism) were conducted to evaluate the influence of level of chopped tall fescue hay (FH) in high concentrate diets on average daily gain (ADG), liquid and particulate passage rates, digestibility and in situ digestibility of corn. In the feedlot trial, 36 Hereford steers were fed diets containing 15, 30 and 50% FH in combination with 74, 59 and 39% whole shelled corn (WSC) and a soybean meal supplement. Steers offered 15, 30 and 50% FH consumed 9.0, 9.0 and 7.6 kg dry matter (DM) per d; gained 1.19, .89 and .67 kg; and had DM to gain ratios of 7.6, 10.1 and 11.5, respectively. A negative correlation was observed between fecal pH and ADG (r = −.52) and between fecal pH and fecal starch (r = −.40). In a 4 × 4 Latin-square trial, four cannulated steers were fed 4, 8, 16 or 24% FH in combination with 86, 82, 74 or 66% WSC and a soybean meal supplement. After 14 d of adaptation, steers were offered ytterbium (Yb)-labelled WSC and were ruminally pulse-dosed with chromium ethylenediaminetetraacetic acid (Cr-EDTA) on the first day of the collection period. Steers fed 4, 8, 16 or 24% FH had the following particulate passage rates: 2.3, 2.7, 2.7 and 2.9%/h from fecal analyses; 2.3, 1.7, 2.4 and 2.8%/h from ruminat analyses; 6.0, 5.3, 6.3 and 8.1%/h for liquid, respectively. With increasing FH level, liquid passage rate exhibited linear and quadratic effects (P<.05), while particulate passage rate (rumen sampling) showed linear and cubic effects (P<.05). The DM and starch digestibilities decreased linearly (P<.05) with increasing FH level, while ADF digestibility increased linearly (P>.05). In situ DM disappearance of corn was not influenced (P>.05) by FH level. Copyright © 1985. American Society of Animal Science . Copyright 1985 by American Society of Animal Science

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