Carcass Quality and Longissimus Tenderness of CalfFed Steers and Heifers Produced Using Alternative

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Carcass Quality and Longissimus Tenderness of
Calf-Fed Steers and Heifers Produced Using
Alternative Growth-Management Strategies D. R.
Woerner and J. D. Tatum Presented at Swift
Seminar May 3, 2007
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Introduction

• Steroidal implants and ß-adrenergic receptor
  agonists (ß-agonists)
• used routinely by U.S. beef producers
• are well documented to increase rate and
  efficiency of growth in cattle
• Use of multiple steroidal implants have been
  shown to produce an additive response (Duckett
  and Andrae 2001).
• Supplementing implanted steers with ractopamine
  hydrochloride (RAC) at 200 mg/hd/d during the
  final 28 to 32 d of finishing solicits an even
  greater response (Laudert et al., 2005).

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Introduction

• To achieve the greatest improvement in growth
  performance
• most calf-fed steers and heifers receive 2
  implants during finishing
• increasing numbers of calf-feds are implanted
  twice and, then, fed RAC for the final 28 to 42 d
  of finishing

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Introduction

• Research suggests that certain growth-management
  strategies produce adverse effects on carcass
  quality, grade performance, and beef product
  tenderness (Schneider et al., 2007)
• In general, implant programs that involve
  sequential use of moderate to high-potency
  implants produce the greatest anabolic response
  and are associated with the most pronounced
  reduction in quality grade and tenderness
  (Duckett, 2004 Schneider et al., 2007).

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Objective

• To determine the effects of alternative growth
  management strategies for calf-fed steers and
  heifers, featuring a reduced number of growth
  promoting implants, on feedlot performance,
  carcass quality, and longissimus muscle (LM)
  tenderness.

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Methodology

• 4 x 2 factorial arrangement in a randomized
  complete block design
• Calf-fed steers (n 231) and heifers (n 146)
  from each source were weighed individually, and
  blocked by weight and sire-breed, within sex
  class.

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Methodology

• Steers and heifers assigned to 1 of 4
  growth-management treatments
• Most anabolic implants, designed for use in
  finishing cattle, are effective for 100 to 130 d
  (Campbell et al., 2005).
• Ideally, terminal implants are administered no
  fewer than 70 d prior to harvest (Morgan, 1997)

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Methodology

• Growth Promotants
• Steers received Revalor-IS initial implants
  (containing 80 mg TBA and 16 mg E2) and
  Revalor-S terminal implants (containing 140 mg
  TBA and 24 mg E2)
• Heifers received Revalor-IH initial implants
  (containing 80 mg TBA and 8 mg E2) and Revalor-H
  terminal implants (containing 140 mg TBA and 14
  mg Estradiol)
• Cattle receiving RAC treatments were offered
  Optaflexx (200 mg RAC/hd/d)

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Methodology

• Slaughter, Carcass Data Collection, and Sampling
• Slaughtered using conventional, humane procedures
• Immediately following slaughter procedures cattle
  received electrical stimulation and were chilled
  for a 48 h period
• Standard carcass traits were collected for USDA
  Yield and Quality grades
• Striploins (IMPS 180) were collected from the
  right sides of each carcass

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Methodology

• Slaughter, Carcass Data Collection, and Sampling
• Striploins
• assigned to a sampling scheme that randomly
  specified anatomical locations of LM section
• assigned to 5 postmortem aging periods (3, 7, 14,
  21, and 28 d)
• LM sections were aged at 2C for each respective
  aging treatment, and frozen at -20C
• LM sections were then fabricated into 2.54 cm
  steaks for Warner-Bratlzer shear force (WBSF) and
  slice shear force analysis (SSF)

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Methodology

• Shear Force Measurements
• SSF (Shackelford et al., 1999) was performed on
  LM steaks aged for 3 d
• WBSF was performed on LM steaks from each of the
  5 aging treatments (3, 7, 14, 21, and 28 d)
• Peak off-temperatures were recorded for each
  steak for statistical analysis

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Methodology

• Statistical Analysis
• Data for BW, ADG, carcass traits, and SSF
• analyzed using the MIXED procedure (SAS Inst.
  Inc., Cary, NC) with animal serving as the
  experimental unit
• Data for WBSF
• analyzed as a repeated measures, using the SAS
  MIXED procedure
• Frequency data (ie. Choice and Prime)
• analyzed using the GLIMMIX procedure of SAS as a
  binomial distribution
• For all analysis
• Kenward-Roger approximation was used to
  calculate denominator degrees of freedom

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Results

• Growth Traits

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Results

• Growth Traits

Final Live Weight
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Results

• Growth Traits
• Heavyweight carcass (gt 950 lbs.)

Final Live Weight
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Results

• Carcass Traits
• Means for adjusted fat thickness and calculated
  yield grade were similar (P gt 0.05)

Final Live Weight
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Results

• The effect of growth-management strategy on
  marbling score approached significance (P 0.067)

Final Live Weight
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Results

• Cattle implanted a single time also exhibited a
  tendency to produce carcasses grading premium
  Choice and Prime (P 0.067)

Final Live Weight
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Results

• Tenderness
• TRT x Age interaction was not significant (P
  0.3816) for WBSF, however, treatment did effect
  WBSF (P 0.0001) and SSF (P 0.024) means

Final Live Weight
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Results

• Tenderness
• TRT x Sex interaction approached significance (P
  0.0583) for WBSF

Final Live Weight
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Results

• Carcass Value
• Two different beef carcass pricing scenarios were
  used to compare carcass value characteristics of
  cattle produced using the 4 growth-management
  strategies modeled to simulate actual commercial
  grid-pricing systems
• A quality-based grid (Scenario 1)
• A yield-based grid (Scenario 2)

Final Live Weight
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Results
Final Live Weight
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Results
Carcass Value
Final Live Weight
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Conclusions

• The results of the present study indicate
• More aggressive growth-management strategies
  effectively increase the rate and efficiency of
  growth in calf-fed steers and heifers.
• Growth-management strategy did not significantly
  impact carcass quality.
• Using a single implant strategy did not show to
  significantly improve LM tenderness when compared
  to a conventional 2-terminal implant program.

Final Live Weight
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Conclusions

• The results of the present study indicate
• However, using RAC in combination with a
  2-terminal implant program proved to be
  detrimental to LM tenderness.
• For feeders that market cattle using
  quality-based pricing systems, use of a single
  implant program may be an economically viable
  strategy for improving beef quality grade
  performance.
• On the other hand, feeders who market cattle on
  weight-driven pricing systems, would achieve
  greater returns by using a 2-implant program

Final Live Weight
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• Questions?