The effects of adding highly digestible fiber to conventional corn-corn silage based growing beef cattle rations

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-1day-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\u3e.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 11 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 1 and 11. Digestion trial 1 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\u3c.05), while lADF gave higher digestibility estimates than Cr2O3 and lignin in digestion trial II (P\u3c.05)