The aim of this study is to investigate the effects of different levels of indigestible neutral detergent fiber (iNDF) in corn silage (CS) and TMR on the ruminal degradability of dry matter (DM) and neutral detergent fiber (NDF), and to compare iNDF content of CS and TMR when analyzed with in situ (288 h) or with in vitro (240 h) methods. The hypothesis of this experiment is that the degradability of DM and NDF is proportionally and negatively associated with iNDF content of feed samples. Dietary treatments will vary in iNDF content (% DM) as follows: 10.24% (IND1),9.57% (IND2),8.25% (IND3), and 8.25% (IND4). The iNDF content of samples was manipulated with different inclusions of corn silage made from plants harvested at 2 heights from the ground level [40 cm (CS40) or 65 cm (CS65)]. All diets had a forage to concentrate ratio 48:52, whereas corn silage was the sole forage source. Corn silage iNDF content was measured by incubating feed samples in the rumen of 2 cows for 288 h. The in situ and in vitro degradability procedures will be performed at the Department of Animal & Dairy Science at the University of Wisconsin, Madison, WI, USA, under supervision of Dr. Ferraretto.
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