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Journal of Animal Science Abstract - Animal Nutrition

In vivo ruminal degradation characteristics and apparent digestibility of low-quality prairie hay for steers consuming monensin and Optimase1


This article in JAS

  1. Vol. 93 No. 8, p. 3941-3949
    Received: Dec 01, 2014
    Accepted: May 08, 2015
    Published: July 2, 2015

    2 Corresponding author(s):

  1. S. K. Linneen*,
  2. A. R. Harding*,
  3. M. T. Smallwood*,
  4. G. W. Horn*,
  5. J. S. Jennings,
  6. C. L. Goad and
  7. D. L. Lalman 2*
  1. * Department of Animal Science, Oklahoma State University, Stillwater 74078
     Agrilife Research and Extension Center, Texas A&M, Amarillo 79106
     Department of Statistics, Oklahoma State University, Stillwater 74078


Seven ruminally cannulated crossbred steers (BW = 720 ± 62 kg) were used in a randomized crossover design (4 periods, each 18 d) to evaluate in vivo rumen characteristics and apparent digestibility of steers consuming low-quality prairie hay and 1 of 4 isonitrogenous protein supplements. Treatments included 1) 40% CP (DM basis) cottonseed meal and wheat middlings–based supplement (Control), 2) 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 (OPT), 3) the Control plus 0.40 mg∙kg–1 BW∙d–1 monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN; MON), and 4) the OPT plus 0.40 mg∙kg–1 BW∙d–1 monensin (COMBO). Steers were allowed ad libitum access to prairie hay (5.0% CP and 76% NDF) and were provided each respective supplement at 0800 h daily at a rate of 1.0 g/kg of BW. Steers were adapted to diets for 10 d before sample collection. Beginning on d 11, DMI was measured and samples were collected to determine apparent digestibility. On d 15 of the 18-d period, rumen fluid was collected 10 times over a 24-h period. Forage DMI was greater (P ≤ 0.02) for steers consuming the OPT compared with steers consuming the MON or COMBO, although forage DMI was not different (P = 0.10) among steers consuming the Control compared with steers consuming the OPT, MON, or COMBO. Steers fed the MON and COMBO had lower (P ≤ 0.05) passage rate compared with steers fed the Control and the OPT. The MON-fed steers had lower (P = 0.01) ruminal pH and increased (P = 0.03) propionate as a percentage of total VFA production. A time × treatment (P = 0.01) interaction was observed for ruminal NH3–N due to a rapid (0 to 1 h after feeding) increase followed by a quick (1 to 4 h after feeding) decline in NH3–N by steers consuming the OPT and COMBO that was not observed for steers consuming all other treatments. Apparent digestibility of DM (P = 0.01) and NDF (P = 0.03) were improved for steers fed the COMBO supplement compared with steers consuming all other experimental supplements. This work suggests that the OPT may be an effective replacement for a portion of supplemental degradable intake protein in low-quality forage. Further research is necessary to determine if the combination of monensin and the Optimase consistently improves low-quality forage utilization.

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