Masters Theses

Date of Award

8-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

John C. Waller

Committee Members

Allan Chestnut, Richard Heitmann

Abstract

One hundred and ninety-two steer calves (275 kg) were randomly allotted to two groups: 24 pens (six steers/pen) with 6.69 M²/steer, and 24 pens (two steers/pen) with 10.03 M²/steer. A 2 by 3 factorial arrangement of dietary treatments was used. Diets consisted of: 1) 100% corn silage (CS); 2) 85% OS, 15% soyhulls (SH); 3) 70% OS, 30% SH; 4) 80% CS, 20% cracked shelled corn (CSC); 5) 65% CS, 20% CSC, 15% SH, and 6) 50% CS, 20% CSC, 30% SH on a dry matter basis. A ground corn grain:soybean meal (2:1) blend provided supplemental protein and was fed at the rate of .68 kg•steer⁻¹•day⁻¹. A mineral mix containing calcium, phosphorus, and salt was offered free choice. In each group, dietary treatments were arranged in a randomized complete block design with four replications. Block involved pen location within a barn. The trials lasted 56 days with the initial weights taken after the animals had been adjusted to their respective diets.

Average daily gains (kg) and feed:gain ratios of group-fed steers for treatments 1 through 6 were: 0.80, 9.92; 0.90, 9.43; 0.82, 12.21; 0.87, 9.25; 0.90, 9.42; and 1.02, 9.09, respectively. Average daily gain (kg) and feed to gain ratios for steers fed in pens containing two steers for treatments 1 through 6 were: 0.56, 13.12; 0.85, 10.52; 0.78, 11.77; 0.67, 11.24; 0.89, 9.85; and 0.90, 11.40, respectively.

Including SH at 15 and 30% of the dietary dry matter resulted in cattle performance similar (P>.05) to the diets of CS or CS plus CSC.

Two digestion trials were conducted toward the end of the 56-day trial using the steers in pens of two. Lignin and indigestible acid detergent fiber (lADF) served as internal markers. Chromic oxide (Cr₂O₃) was used as an external marker and was mixed with ground corn grain and fed at the rate of 29.768g/day for seven days prior to the collection period. Fecal grab samples were collected at random two-hour intervals representative of a 24- hour period, over a total of 4 (digestion trial I) and 6 days (digestion trial II).

Average dry matter (DM), organic matter (OM), acid detergent fiber (ADF), and neutral detergent fiber (NDF) digestibilities during digestion trial I for treatments 1 through 6 were: 68.16, 69.90, 51.76, 59.46; 71.37, 72.87, 61.30, 65.39; 72.20, 73.72, 65.80, 67.83; 71.08, 72.62, 49.94, 58.74; 74.21, 75.58, 61.81, 66.12; and 72.55, 73.65, 66.60, 67.74, respectively. Average DM, OM, ADF, and NDF digestibilities during digestion trial II for treatments 1 through 6 were: 68.27, 70.12, 52.73, 59.73; 69.67, 71.09, 58.83, 63.08; 70.81, 72.34, 64.17, 66.42; 69.09, 70.54, 48.99, 56.86; 70.34, 71.75, 58.83, 62.03; and 70.31, 71.43, 62.60, 64.41, respectively.

Digestibilities of DM, OM, ADF and NDF increased as SH were included in CS or CS-CSC blend diets in both digestion trials I and II. Digestion trial I resulted in slightly higher digestibility estimates than digestion trial II in steers fed treatments 2 through 6.

Chromic oxide gave significantly lower estimates of DM, CP, OM, ADF and NDF digestibility than either lignin or lADF in digestion trial I (P<.05), while lADF gave higher digestibility estimates than Cr₂O₃ and lignin in digestion trial II (P<.05).

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