Woodchip Bedding in Wet Feedlot Cattle – Key Findings and Concepts

Objective

• Assess effects of graded woodchip bedding levels on performance, behaviour, and chronic stress (adrenal gland weight) in feedlot cattle under cold, wet, non-freezing winter conditions.
• Treatments: No bedding (Control), woodchip at 15\,\text{cm} (W15), woodchip at 30\,\text{cm} (W30).
• Experimental unit: pen; design = randomized block with n=10 pens per treatment; cattle per pen = 10; study duration = 109 days.
• Environment: Pens on soil base with irrigation to reach total precipitation ~74\,\text{mm/30 days}; temperatures largely <20^{\circ}\mathrm{C} max and -1$\sim$5^{\circ}\mathrm{C} min.

Experimental design and housing

• Species: Bos taurus steers (n = 300); weight-stratified blocks, mixed breeds.
• Pens: 6.25 m × 20 m; slope ~-3^{\circ} (front to back); space = 12.5\ \text{m}^2/\text{steer}; feed bunk space ≈ 31.25\ \text{cm/steer}; shared water trough.
• Substrates: Treatment pens had a manure interface with a woodchip layer (W15 or W30) on top of a clay/rock base; end-point penetrable depths recorded as: Control ~20 cm, W15 ~14 cm, W30 ~6 cm.
• Management: Sick cattle moved to a hospital pen; density maintained; vaccination and growth promotant protocols described in study.

Treatments

• Control: manure interface only (no bedding).
• W15: woodchip bedding depth of 15\,\text{cm}.
• W30: woodchip bedding depth of 30\,\text{cm}.

Diet and feeding management

• Finisher diet with stages: Starter, Intermediate I, Intermediate II, Finisher; barley-based with water addition to achieve moisture 14$\sim20\%.
• Diet composition (DM basis) and ME/NDF/ADF listed in the study; feed delivered once daily as a total mixed ration.
• Bunk management: orts monitored; adjustments made to feed delivery to keep orts < 0.5\ \text{kg/head}.

Measurements and data collection

• Growth performance: individual BW on days 0, 28, 56, 92, 109; ADG; DMI (pen level);
  • final liveweight (adjusted using dressing percentage), Hot Standard Carcass Weight (HSCW).
• Carcass characteristics: HSCW; dressing percentage; P8 fat; rib fat; MSA marbling index; EMA; ossification; ultimate pH; glycogen content.
• Physiological indicator of chronic stress: relative adrenal gland weight = (best adrenal gland weight in g) / (final liveweight in kg) × 100.
• Behaviour and pen use: UAV imagery to classify front/middle/back pen zones; posture (standing/lying) and activity (eating/drinking) by zone; dag score (coat condition) weekly.
• Coat/dag scoring and other welfare metrics analyzed with appropriate models as described in study.

Key production results

• Growth and efficiency:
  • After day 28, both W15 and W30 improved liveweight gain vs. Control (P < 0.001 for LW gain; P = 0.012 for G:F advantage with woodchip).
  • Final body weight: Control 622.2\,\text{kg}; W15 647.7\,\text{kg}; W30 648.9\,\text{kg} (P < 0.001).
  • Adjusted final BW: Control 626.3\,\text{kg}; W15 644.2\,\text{kg}; W30 646.6\,\text{kg} (P = 0.003).
  • ADG 0–109 days: Control 2.26\ \text{kg/d}; W15 2.45\ \text{kg/d}; W30 2.48\ \text{kg/d} (P < 0.001).
  • DMI 0–109 days: Control 11.3\ \text{kg DM/head/d}; W15 11.8\ \text{kg DM/head/d}; W30 11.5\ \text{kg DM/head/d} (P = 0.049).
  • G:F: overall improvement with bedding; by end, W30 had higher G:F than W15 (P = 0.012).
• Maintenance energy and intake dynamics:
  • Maintenance ME requirement estimated from ADG vs ME intake; Control showed higher maintenance ME requirement, consistent with wetter, muddier pen conditions.
  • DMI increases in bedded pens did not fully explain gains, indicating improved feed efficiency due to reduced maintenance costs or enhanced energy capture.

Key carcass outcomes

• Hot Standard Carcass Weight (HSCW): woodchip bedding increased mean HSCW by +9.3\sim+10.8\ \text{kg} for W15 and W30, respectively (P = 0.001).
• Dressing percentage: minor differences, not biologically meaningful across treatments (P = 0.023 for some contrasts).
• Muscle glycogen: W15 higher than Control and W30 (P = 0.047).
• Eye muscle area (EMA): greater in W30 vs. Control after covariate adjustment (P = 0.041).
• MSA index and pH: no meaningful treatment effect; one carcass downgraded due to pH > 5.70 (W30).
• Overall: woodchip bedding improved carcass weight without adverse effects on marbling, pH, or rib fat.

Welfare, behaviour, and physiological indicators

• Coat and dag scores:
  • Induction coats were rough; by end, most coats were smoother (P < 0.001).
  • Dag scores higher in Control, with an interaction over weeks; Control higher than bedded groups up to week 6 and at several later weeks (P = 0.002 for interaction).
  • No clear association between dag score and G:F within treatments.
• Pen-use distribution (UAV-based):
  • Control steers more frequently in the front of the pen (P < 0.05 from week 6 onward).
  • W15 and W30 steers more often in the middle of the pen (weeks 6–16; weeks 10–14, respectively) (P < 0.05).
  • Front-pen location linked to proximity to feed bunk and drainage concerns; woodchip bedding shifted use away from the front zone, suggesting less aversive conditions there.
• Lying and activity:
  • Proportion lying higher in Control overall (P = 0.015), with bedded steers showing more lying in the mid-to-back areas as the study progressed.
  • Proportion eating declined over time, but no main effect of bedding on eating time (P = 0.430).
• Adrenal gland weight (chronic stress proxy):
  • Relative adrenal weight tended to be higher in Control (approx. 4.18\pm0.289\ \text{g}/100\ \text{kg HSCW}) than in W30 (≈ 3.91\pm0.232\ \text{g}/100\ \text{kg HSCW}) (P = 0.077).
  • New lower maintenance energy needs in bedded groups align with welfare indicators suggesting reduced chronic stress.

Pen surface, mud and environmental considerations

• Pen surface in Control deteriorated more than woodchip pens by day 109; greater mud depth and wetter substrate in Control pens likely increased energetic costs and reduced comfort.
• Woodchip pads produced a drier surface and allowed cattle to stand on a woodchip layer rather than sinking into mud, supporting better welfare and performance outcomes.

Conclusions and practical implications

• Minimum woodchip depth of 15\,\text{cm} improves performance and welfare indicators in wet, cold conditions over 109 days, with a tendency toward reduced chronic stress (adrenal gland weight).
• No clear extra growth benefit from doubling depth to 30\,\text{cm} for most metrics, though G:F advantage persisted longer in W30 than W15 toward the end of the period.
• Woodchip bedding did not increase intake; benefits are mainly through reduced maintenance energy costs and possibly better heat retention and lower mud-related activity costs.
• Bedding also redistributed pen-use, reducing front-end crowding and exposing cattle to more comfortable substrate surfaces.
• Recommendation: in similar wet, cold feedlot scenarios, provide at least 15\,\text{cm} woodchip bedding to boost growth efficiency and welfare; consider 30\,\text{cm} if the goal includes maximizing G:F late in the feeding period.

Ethics and transparency

• Study approved by the University of New England Animal Ethics Committee; no AI-assisted writing used in manuscript.
• Data and models not deposited in a public repository; manuscript conclusions based on reported analyses.

Key terms to recall

• G:F: gain-to-feed ratio; a measure of feed efficiency.
• HSCW: Hot Standard Carcass Weight.
• MSA index: predicted eating quality index in carcasses.
• Eucalyptus woodchip bedding: the intervention tested.
• Dags: coat condition score related to manure adherence; higher dags can relate to welfare signals.
• Relative adrenal weight: proxy for chronic stress under housing/conditioning.