Document Type

Thesis - University Access Only

Award Date

1998

Degree Name

Master of Science (MS)

Department / School

Animal Science

Abstract

A 70-d growing steer trial along with harvesting data were used to evaluate the relative feed value of a high fiber silage variety (CSV 1) versus a conventional corn silage variety (CSV2). Varieties were harvested over 2 d as chopped whole plants and allowed to ferment for 52 d in bunker silos. CSV l yielded 41. 0 T/ha (29.3% DM), while CSV2 yielded 36.0 T/ha (28 .0% DM). Diets containing 88.6% corn silage and 11. 4% pelleted supplement (DM basis) were fed to 160 steer calves. Calves were blocked by initial BW into light (234 ± 3.2 kg) and heavy (270 ± 4.4 kg) groups. There were 10 pens of steers assigned to each treatment. Implanted (Ralgro) steers were fed once daily. Final BW included a 3% shrink. Pens were considered the experimental unit. Ingredient samples were collected weekly and analyzed. The CP, starch, NDF, ADF and lignin composition of the silages differed (P<.01). Digestibilities measured by IVDMD were similar between varieties. CSV2 caused a higher (P<. 10) ADG and greater (P<.05) G/F than CSV 1. Dry matter intake did not differ (P>.10) between treatments. Correcting G/F to

100% corn silage and multiplying by harvest yield/ha (DM basis) resulted in CSV 1 producing 2284 kg of beef/ha compared to 2026 kg of beef/ha produced by CSV2. Indirect respiratory calorimetry was conducted to compare caloric density of both silages. Six steers (BW = 338 ± 23 kg) were paired (2 steers/group) according to BW and randomly assigned to silage variety. Diets similar to the feedlot trial were fed at 90% ad libitum twice daily. Total urine and feces output were collected for 6 d. Oxygen consumption and CO2 and methane production were measured for 2 consecutive days on each steer. Nitrogen, NDF and ADF digestibilities were similar (P>. l 0) between treatments. The NEm (1.78 Meal/kg vs 1.77 Meal/kg) and NEi: (1. 15 Meal/kg vs 1.14 Meal/kg) values were similar (P>. 10) for CSVI and CSV2, respectively. Energy values calculated using the calorimetry trial were compared to energy values predicted using lab analyses and feedlot performance data. No differences were detected (P>.05) in the NEm and NEg values determined by the three methods within a treatment. Similar calculated energy values support the use of proximate analysis to evaluate caloric density. The data indicate limitations in selecting a variety based on a single characteristic, such as proximate analysis or yield.

Library of Congress Subject Headings

Cattle -- Feeding and feeds Corn -- Silage Fiber in animal nutrition Feeds -- Fiber content

Format

application/pdf

Number of Pages

69

Publisher

South Dakota State University

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