View Full Table | Close Full ViewTable 1.

Supplement composition and amount of nutrients supplied daily to steers

 
Treatment1
Control
OPT
MON
COMBO
Item % of DM
Cottonseed meal 86.3 42.5 86.3 42.5
Wheat middlings 8.09 31.8 7.90 31.7
Cane molasses 5.50 5.50 5.50 5.50
Soybean hulls 10.0 10.0
Corn 5.00 5.00
Optimase 5.00 5.00
Rumensin 90 0.19 0.19
Vitamin A, 30,000 IU/g2 0.11 0.11 0.11 0.11
Vitamin E acetate 50% 0.05 0.05 0.05 0.05
Nutrient supplied, kg/d3
    DM 0.71 0.75 0.76 0.77
    CP 0.33 0.34 0.34 0.35
    TDN 0.63 0.62 0.65 0.63
    Crude fat 0.01 0.02 0.01 0.02
Chemical composition, %
    DM 90.0 89.7 90.0 89.7
    CP 40.1 40.8 40.1 40.8
    TDN 76.2 74.0 76.0 74.0
1Control = 40% CP (DM basis) cottonseed meal and wheat middlings–based supplement; OPT = a cottonseed meal and wheat middlings–based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control; MON = the Control plus 0.40 mg∙kg–1 BW∙d–1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN); COMBO = the OPT plus 0.40 mg∙kg–1 BW∙d–1 monensin.
2Provided 32,960 IU of vitamin A per kilogram of supplement DM.
3Calculated based on average steer daily feed allotment per treatment for all periods.\



View Full Table | Close Full ViewTable 2.

Effects of feeding monensin and Optimase on DMI, rumen fill, and passage rate

 
Treatment1
Item Control OPT MON COMBO SE2 Probability, P <
No. of observations 7 7 7 7
Average BW, kg 711 715 727 728 15.9 0.32
Forage DMI, % of BW 1.08ab 1.22a 1.04b 1.02b 0.05 0.07
Rumen contents
    Fill, % of BW 1.79 1.75 1.53 1.53 0.32 0.88
    ADIA,2 % 3.20 3.37 3.38 3.39 0.11 0.66
    Passage rate (Kp3), %/h 1.41a 1.46a 0.83b 1.01b 0.07 0.05
a,bMeans within a row with different superscripts differ (P < 0.05).
1Control = 40% CP (DM basis) cottonseed meal and wheat middlings–based supplement; OPT = a cottonseed meal and wheat middlings–based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control; MON = the Control plus 0.40 mg∙kg–1 BW∙d–1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN); COMBO = the OPT plus 0.40 mg∙kg–1 BW∙d–1 monensin.
2ADIA = acid detergent insoluble ash.
3Kp = fractional passage rate of ADIA.



View Full Table | Close Full ViewTable 3.

Effects of feeding monensin and Optimase on apparent digestibility of DM, NDF, ADF, and CP

 
Treatment1
Item Control OPT MON COMBO SE2 Probability, P <
Apparent digestibility, %
    DM 63.0b 60.5b 62.0b 68.2a 1.48 0.01
    NDF 64.5b 60.9b 63.3b 69.8a 1.87 0.03
    ADF 57.5ab 46.2c 53.4b 60.5a 1.79 <0.01
    CP 52.9 53.1 51.3 58.9 3.72 0.47
a–cMeans within a row with different superscripts differ (P < 0.05).
1Control = 40% CP (DM basis) cottonseed meal and wheat middlings–based supplement; OPT = a cottonseed meal and wheat middlings–based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control; MON = the Control plus 0.40 mg∙kg–1 BW∙d–1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN); COMBO = the OPT plus 0.40 mg∙kg–1 BW∙d–1 monensin.
2Represents the average SE.



View Full Table | Close Full ViewTable 4.

Effects of feeding monensin and Optimase on ruminal pH and VFA

 
Treatment1
Item Control OPT MON COMBO SE2 Probability, P <
Ruminal pH 6.87a 6.88a 6.75b 6.96a 0.04 <0.01
VFA, % of total
    Acetate 74.4a 74.2a 72.4b 73.3ab 0.58 0.07
    Propionate 15.8b 16.0b 18.6a 18.0ab 0.79 0.10
    Butyrate 9.6 9.8 9.2 9.3 0.24 0.11
    Acetate:propionate 4.85a 4.86a 3.95b 4.07b 0.24 0.05
    Total VFA, mg/dL 70.4 78.5 66.9 71.3 3.09 0.23
a,bMeans within a row with different superscripts differ (P < 0.05).
1Control = 40% CP (DM basis) cottonseed meal and wheat middlings–based supplement; OPT = a cottonseed meal and wheat middlings–based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control; MON = the Control plus 0.40 mg∙kg–1 BW∙d–1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN); COMBO = the OPT plus 0.40 mg∙kg–1 BW∙d–1 monensin.
2Represents the average SE.