Document Type

Thesis - University Access Only

Award Date

2006

Degree Name

Master of Science (MS)

Department / School

Animal Science

Abstract

Two experiments were conducted to detennine the effect of feeding increasing concentrations of dried distillers grains with solubles (DDGS) on finishing steer performance, feedlot nutrient management, and odorant emissions. In experiment one (Exp. 1), 199 steers (BW = 386 ± 8 kg), were blocked by source, stratified by weight, and allotted to 16 dirt floor pens (14.7 m x 34.7 m). Pens were then randomly assigned to one of four dietary treatments. The control diet (CON) contained 82% cracked com, 10% alfalfa hay, 4% molasses, 3.2% supplement, and 0.8% urea on a dry matter basis. In the remaining three diets, all of the urea and some of the cracked com were removed and replaced with DDGS at 15% (15% DOGS), 25% (25% DDGS), and 35% (35% DDGS) of the diet DM. Diets were balanced to provide similar levels of crude protein (CP) for CON and 15% DDGS (13.2 and 13. 3% CP, respectively) and a stepwise increase in CP for 25% DDGS and 35% DDGS (15.4 and 17.6%, respectively). Weights were recorded prior to feeding on d-1, 0, 105, and every intermediate 28 d. Over the entire feeding period (d 0 - 105), dry matter intake (DMI) was greater (P = 0.02) for 25% DDGS compared to CON. There was also a trend (P = 0.07) for greater average daily gain (ADG) in steers fed 25% DDGS compared to CON. When analyzed as a contrast, dressing percentage was lower (P = 0.01) for CON than for DDGS-fed cattle. Backfat increased linearly (P = 0.01) as DDGS inclusion increased. Hot carcass weights and dressing percentage tended (P < 0.06) to increase as the level of DDGS in the diet increased. No differences were detected between treatments for marbling, ribeye area (REA), or kidney, pelvic and heart fat (KPH). Air samples were collected via wind tunnel at 3 locations per pen over 3-d periods prior to animal introduction and on d 78-80. Hydrogen sulfide levels in the air samples were greatest (P = 0.01) in pens containing cattle fed the 35% DDGS treatment compared to pens with cattle fed the remaining treatments. Odor was analyzed from air samples using dynamic, triangular, forced choice ol factometry. No differences in odor characteristics were detected between treatments. Soil samples were taken from pen floors prior to animal introduction and at the conclusion of the feeding period after the removal of surface manure. Soil cores (0-15 cm) were taken from seven locations in each pen, pooled within pen, and chemically analyzed for organic matter (OM), nitrate nitrogen ( 03- ), ammonia nitrogen (NH.i- ), Kjeldahl nitrogen (Kjeldahl- ), Olsen phosphorus (Olsen-P), pH, salts and potassium (K). Manure removed from pens after animal removal was weighed wet, sub-sampled, and analyzed for DM, Olsen-P, H4- , and Kjeldahl- . There was a trend (P = 0.13) for an increase in Olsen-P and H4- in pen floor core samples between initial and final sampling periods for pens where cattle were fe d 35% DDGS relative to all other treatments. Olsen-P and H4- in manure removed from pens increased linearly (P <0.001), as the levels of DDGS in the diet increased. Experiment two (Exp. 2) was conducted to determine the effect of increasing dietary concentrations of DDGS on phosphorus (P) balance. Eight steers (BW = 442 ±15 kg) were utilized in a replicated Latin Square design with 21-d acclimation periods and 5-d collection periods. One steer was removed from the experiment because of physical ailments that prevented it from standing in the metabolism stanchion. All of the data from this steer was omitted from analyses. Animals were assigned to one of four dietary treatments. The control diet (CON) contained 79% cracked corn, 1 0% cottonseed hulls, 6% soybean meal, and 5% supplement on a dry matter basis. In the remaining three diets, all of the soybean meal and some of the cracked com were removed and replaced with DDGS at 12% (12% DDGS), 24% (24% DOGS), and 36% (36% DDGS) of the diet DM. During collection periods, total fecal and urinary output was collected, weighed, sub-sampled, and pooled by animal within period. Total P was analyzed in individual feed ingredients, feed refusals, feces, and urine. Urine P content was greater (P = 0.04) for steers received 24% and 36% DDGS compared to those that received CO and 12% DDGS. Urine P increased linearly (P < 0.00 1) as levels of DOGS in the diets increased. Fecal P was not different between treatments. Total P excretion tended (P = 0.09) to be greater in steers fed 24% DDGS vs CON or 12% DDGS, but was not different from those fed 36% DDGS. Steers that received 36% DDGS excreted more (P = 0.08) P than CON. Phosphorus retention was lower (P = 0.04) for CON than for all other treatments except 12% DDGS. Both retention and excretion of P increased linearly (P = 0.02 and 0.03, respectively) as the level of DDGS in the diets increased. As P intake increased, fecal P, total P excreted, and P retention increased (P < 0.01), and urine P tended to increase (P =0.11. Key words: distillers grains, odor, nutrient management, phosphorus

Library of Congress Subject Headings

Beef cattle -- Feeding and feeds

Distillers feeds

Beef cattle -- Odor

Format

application/pdf

Number of Pages

84

Publisher

South Dakota State University

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