Economic Reality
In feedlot cattle production, 65-75% of total cost is usually feed expense. Improving feed conversion ratio (FCR) by just 0.5 points can create a major economic advantage over a 300-day feeding period.
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Calculate the Ration1. Definition of Feedlot Phases and Their Physiological Foundations
The feedlot process is divided into three major phases according to the animal's stage of physiological development and its tissue deposition priority. Understanding these phases is the basis of sound ration design. The growth curve model described by Owens et al. (1995) shows that tissue deposition progresses in the sequence of bone → muscle → fat.
- Goal: Rumen adaptation and stress control
- DMI: 1.5-2.0% of body weight
- Concentrate proportion: 30-50% with gradual increases
- Target ADG: 0.5-1.0 kg/day
- Critical risks: BRD, acidosis, bloat
- Main tissue deposition: Bone > Muscle
- Goal: Skeletal growth and muscle development
- DMI: 2.2-2.8% of body weight
- Concentrate proportion: 55-70%
- Target ADG: 1.2-1.6 kg/day
- Protein requirement: Highest in the whole program
- Main tissue deposition: Muscle > Bone > Fat
- Goal: Fat deposition and carcass quality
- DMI: 2.0-2.5% of body weight
- Concentrate proportion: 75-90%
- Target ADG: 1.4-1.8 kg/day
- Energy requirement: Highest phase
- Main tissue deposition: Fat > Muscle
1.1 Physiology of Tissue Deposition and Energy Partitioning
Growth in cattle is shaped by the interaction between genetic potential and nutritional supply. Early in the feedlot program, energy is directed primarily toward protein deposition (muscle synthesis); later, it is increasingly diverted toward lipogenesis (fat deposition). This physiological shift is the scientific basis for adjusting dietary energy and protein density by phase (NRC, 2000; NASEM, 2016).
Efficiency of Energy Use (NASEM, 2016)
| Tissue Type | Energy Content (Mcal/kg) | Synthesis Efficiency | Relative Importance by Phase |
|---|---|---|---|
| Muscle (protein) | 5.7 Mcal/kg protein | 20-30% (low) | Mainly early to mid feedlot period |
| Fat (lipid) | 9.4 Mcal/kg fat | 60-75% (high) | Mainly late feedlot period |
| Bone | Low | Variable | Very early growth period |
Fat synthesis is more energy-efficient than protein synthesis; for that reason, FCR often improves in the finishing phase, although the composition of gain shifts toward greater fat deposition.
2. Feeding During the Adaptation Phase (0-28 Days)
The adaptation phase lays the foundation for feedlot success. Errors made during this period can compromise the entire feeding program. Newly received cattle are exposed to transport stress, environmental change, and social stress. The risk of respiratory disease complexes (BRD) is highest during this phase (Duff & Galyean, 2007).
2.1 Ration Strategy for the Adaptation Phase
Golden Rule: Make the Transition Gradual
The proportion of concentrate should not be increased by more than 10-15 percentage points per week. Abrupt increases can trigger ruminal acidosis, feed refusal, and even mortality. The adaptation period should last at least 21-28 days, and ideally use a 4-step ration program.
| Step | Days | Concentrate (% DM) | Forage (% DM) | NEm (Mcal/kg) | CP (% DM) |
|---|---|---|---|---|---|
| Step 1 | 1-7 | 30-35 | 65-70 | 1.40-1.50 | 13-14 |
| Step 2 | 8-14 | 45-50 | 50-55 | 1.55-1.65 | 13-14 |
| Step 3 | 15-21 | 60-65 | 35-40 | 1.70-1.80 | 12-13 |
| Step 4 | 22-28 | 70-75 | 25-30 | 1.85-1.95 | 12-13 |
2.2 Critical Management Points During Adaptation
Health Management
- BRD prophylaxis: Arrival vaccination against IBR, BVD, PI3, BRSV, Mannheimia, and Pasteurella where indicated
- Parasite control: Broad-spectrum antiparasitic treatment such as ivermectin or doramectin
- Metaphylaxis: Arrival antibiotic protocols in high-risk groups when justified by herd risk
- Daily observation: Nasal discharge, coughing, poor appetite, depression
- Rectal temperature: ≥40°C should trigger the treatment protocol
Water and Feed Access
- Water: Provide immediate access to clean drinking water on arrival
- First feed: Good-quality hay such as alfalfa or grass hay
- Concentrate start: Introduce gradually from day 2 or 3
- Bunk space: Minimum 45-60 cm per animal
- Water points: One drinking point per 15-20 animals
Rumen Microbiota Adaptation
In cattle previously fed forage-heavy diets, cellulolytic bacteria such as Fibrobacter and Ruminococcus dominate the rumen. During the shift to concentrate feeding, amylolytic bacteria such as Streptococcus bovis and Lactobacillus proliferate and lactic acid production increases. The absorptive capacity of rumen papillae for VFAs takes 4-6 weeks to improve fully. High-concentrate feeding before this adaptation is complete can lead to acute or subacute ruminal acidosis (Nagaraja & Titgemeyer, 2007).
3. Feeding During the Growing Phase (29-120 Days)
The growing phase is the period when skeletal growth is largely completed and lean tissue deposition is most active. During this phase, protein quality and quantity are especially important because muscle synthesis requires an adequate and balanced amino acid supply. Insufficient energy limits muscle gain, whereas excessive energy can cause premature fattening and reduce carcass value (Owens et al., 1995).
3.1 Nutrient Requirements in the Growing Phase
| Parameter | Target (NASEM, 2016) | Explanation |
|---|---|---|
| NEm | 1.80-2.00 Mcal/kg DM | Moderate to high energy density |
| NEg | 1.15-1.35 Mcal/kg DM | Net energy for growth |
| CP | 12.5-14.0% DM | Enough protein to support muscle development |
| MP (Metabolizable Protein) | 800-1000 g/day | RDP:RUP balance matters |
| RDP | 60-65% of CP | Supports rumen microbial protein synthesis |
| RUP | 35-40% of CP | Bypass protein is especially relevant in young cattle |
| NDF | 18-25% DM | Minimum effective fiber for rumen function |
| Ca | 0.50-0.70% DM | Supports skeletal development |
| P | 0.30-0.40% DM | Target Ca:P ratio is 1.5-2.0:1 |
3.2 Protein Sources and Protein Quality
During the growing phase, protein quality directly influences lean tissue gain. Young cattle have high requirements for metabolizable protein (MP), and amino acid balance becomes more important. Lysine and methionine are the main limiting amino acids under many practical conditions (Klemesrud et al., 2000).
- Soybean meal (48% CP): Reference protein source with high rumen degradable protein
- Cottonseed meal: Moderate quality; monitor gossypol exposure
- Sunflower meal: Useful amino acid profile
- DDGS: High RUP, contributes both energy and protein
- Blood meal: Very high RUP, strong lysine source
- Fish meal: High quality; contributes methionine
- Urea: Should not exceed 1% of the total ration on a DM basis
- Upper limit: No more than 30% of total dietary nitrogen should come from NPN
- Condition: Adequate fermentable energy must be present
- Caution: Do not use urea in the adaptation phase
- Toxicity risk: >0.5 g/kg body weight may lead to ammonia intoxication
- Slow-release urea: A safer alternative in some finishing systems
4. Feeding During the Finishing Phase (121+ Days)
The finishing phase is the final stage, when fat deposition accelerates and carcass quality is largely determined. During this period, dietary energy density is pushed to its highest level while protein concentration is relatively reduced. The aim is to increase intramuscular fat deposition (marbling) and improve carcass grade (Owens & Gardner, 2000).
4.1 Nutrient Requirements in the Finishing Phase
| Parameter | Target | Explanation |
|---|---|---|
| NEm | 2.05-2.20 Mcal/kg DM | High energy density |
| NEg | 1.35-1.55 Mcal/kg DM | High energy supply for fat deposition |
| CP | 11.5-13.0% DM | Relative protein requirement declines |
| NDF | 12-18% DM (minimum) | Critical lower limit for rumen health |
| Concentrate proportion | 75-90% DM | High-grain energy-dense feeding |
| Fat | 3-6% DM total | May be supported with DDGS or added fat |
| Ca | 0.50-0.70% DM | High-grain diets require close Ca:P balance control |
| K | 0.60-0.70% DM | May be inadequate in high-concentrate rations |
4.2 Grain Processing and Starch Digestibility
In the finishing phase, grain often accounts for 60-75% of the ration. The processing method used for grain directly affects starch digestibility and therefore dietary energy value. Owens et al. (1997) showed that steam flaking can increase starch digestibility of corn by 15-20%.
| Grain Processing Method | Starch Digestibility | Effect on FCR | Acidosis Risk |
|---|---|---|---|
| Whole grain | 70-80% | Reference | Low |
| Dry rolling/cracking | 80-88% | 3-5% improvement | Moderate |
| Fine grinding | 88-95% | 5-8% improvement | High |
| Steam flaking | 92-98% | 8-12% improvement | Moderate to low |
| High-moisture corn | 90-96% | 6-10% improvement | Moderate to high |
Choosing Grain Sources Under Turkish Conditions
In Turkish feedlot systems, the most common grain sources are barley and wheat. Barley ferments more slowly than corn and generally carries a somewhat lower acidosis risk. Wheat ferments very rapidly and carries a high acidosis risk; it should usually remain below 40% of the ration and must be fed cracked or rolled rather than finely ground. If corn is used, rolling or coarse cracking is usually adequate; excessive grinding increases acidosis risk.
5. Feed Conversion Ratio (FCR) and Optimization
FCR (Feed Conversion Ratio) expresses the amount of feed required to produce 1 kg of live weight gain and is one of the most important indicators of feedlot profitability. A lower FCR means greater biological and economic efficiency.
FCR Calculation
FCR = Total Feed Intake (kg DM) ÷ Total Live Weight Gain (kg)
Example: If a steer consumes 2400 kg of DM in 300 days and gains 450 kg of live weight, then FCR = 2400/450 = 5.33.
| Feedlot Phase | Target FCR | Target ADG (kg/day) | Main Influencing Factors |
|---|---|---|---|
| Adaptation | 7.0-9.0 | 0.5-1.0 | Stress, low DMI, disease |
| Growing | 5.5-7.0 | 1.2-1.6 | Protein quality, energy density |
| Finishing | 5.0-6.5 | 1.4-1.8 | Energy density, breed, sex |
| Total feedlot period | 5.5-7.0 | 1.2-1.5 (average) | Breed, starting weight, days on feed |
5.1 Factors That Influence FCR
- Ionophore use: FCR may improve by 5-8% with monensin
- Grain processing: Steam flaking may reduce FCR by 8-12%
- Genetic selection: Animals with low residual feed intake (RFI)
- Optimal protein supply: Meeting MP requirements consistently
- Health control: BRD can worsen FCR by 15-20%
- Environmental comfort: Managing THI and heat load
- Disease: BRD, acidosis, lameness
- Heat stress: THI >74 lowers DMI and worsens FCR
- Cold stress: <−10°C increases maintenance energy demand
- Overlong feeding period: Late fattening tends to deteriorate efficiency
- Inadequate water: DMI and ADG both decline
- Social stress: Overstocking and excessive mixing
- Beef breeds: Angus, Hereford often achieve FCR 5.0-6.0
- Dual-purpose breeds: Simmental often 5.5-6.5
- Dairy breeds: Holstein often 6.5-8.0
- Intact males: Usually 10-15% more efficient
- Steers: Often show more marbling
- Heifers: Tend to have the highest FCR and earlier fattening
6. Feed Additives and Growth-Support Strategies
6.1 Ionophores
Ionophores such as monensin and lasalocid are antibiotic-like feed additives that modify rumen fermentation by increasing propionate production and reducing methane losses. They are among the most widely used additives in commercial feedlot cattle systems (Duffield et al., 2012).
| Ionophore | Dose | Mechanism of Action | Expected Result |
|---|---|---|---|
| Monensin (Rumensin®) | 25-33 mg/kg DM (200-360 mg/head/day) | Inhibits Gram-positive bacteria → propionate ↑, acetate ↓, methane ↓ | FCR ↓ by 5-8%, lower acidosis risk, lower bloat risk |
| Lasalocid (Bovatec®) | 25-33 mg/kg DM | Similar to monensin, with a somewhat broader spectrum | FCR ↓ by 4-6%, usually less suppressive on DMI |
6.2 Other Additives
| Additive | Dose | Primary Effect | Strength of Evidence |
|---|---|---|---|
| Live yeast (S. cerevisiae) | 1-5 × 10⁹ CFU/day | Stabilizes rumen pH, may improve fiber digestion | Strong, especially during adaptation |
| Sodium bicarbonate | 0.5-1.0% DM (50-100 g/day) | Rumen buffering, SARA prevention | Strong |
| Tylosin phosphate | 8-10 g/ton of feed | Helps reduce liver abscess incidence | Strong in high-concentrate diets |
| β-agonists (zilpaterol, ractopamine) | Varies by country | Muscle deposition ↑, fat deposition ↓ | Strong, but not legal in Turkey |
| Essential oils | Depends on the product | Antimicrobial effects and rumen modulation | Moderate; studied as antibiotic alternatives |
| Tannins | 1-3% DM | Protein protection, methane ↓, antiparasitic support | Moderate to strong |
Legal Status in Turkey
In Turkey, β-agonists such as zilpaterol and ractopamine, as well as hormonal growth promotants, are prohibited. Ionophores such as monensin and lasalocid may be used under veterinary prescription. Antibiotic growth promotants have been banned in line with EU legislation. Live yeast, buffers, and essential oils may be used more freely within product-specific regulations.
7. Management of Metabolic Risks
7.1 Ruminal Acidosis
Ruminal acidosis is one of the most common and costly metabolic disorders in feedlot cattle. It is characterized by a fall in rumen pH caused by rapid fermentation of high-concentrate diets (Nagaraja & Lechtenberg, 2007).
- Rumen pH: <5.0
- Cause: Sudden high grain intake
- Clinical signs: Anorexia, diarrhea, dehydration, shock
- Complications: Laminitis, liver abscesses, rumenitis
- Mortality: Often 5-10%, and higher without intervention
- Treatment: Rumen lavage, IV fluids, bicarbonate, and intensive support
- Rumen pH: 5.0-5.5 for more than 3 hours per day
- Cause: Chronic high-concentrate feeding with insufficient effective fiber
- Clinical signs: Variable intake, soft feces, lameness
- Complications: Liver abscesses and laminitis are common
- Economic loss: ADG ↓ by 10-15%, FCR worsens by 10-20%
- Prevention: Effective fiber, buffers, and ionophores
7.2 Liver Abscesses
Liver abscesses occur with a 15-30% prevalence in feedlot cattle receiving high-concentrate diets. The usual pathophysiologic sequence is rumenitis → portal bacteremia → hepatic abscess formation. Fusobacterium necrophorum and Trueperella pyogenes are the organisms most often isolated (Nagaraja & Chengappa, 1998).
Liver Abscess Prevention Strategies
- Adequate effective NDF: At least 8-10% physically effective NDF
- Tylosin phosphate: 8-10 g/ton of feed where legal and prescribed
- Gradual ration transition: Strict adherence to the step-up program
- Ionophores: Additional support for rumen pH stability
- Feeding management: Deliver feed two or more times per day at consistent times
7.3 Bloat
Emergency: Feedlot Bloat
Foamy feedlot bloat can occur in high-concentrate cattle feeding systems.
- Cause: Finely ground grain, insufficient forage, and stable foam formation from rumen contents
- Emergency treatment: Oral poloxalene (25-50 g), with trocarization reserved for life-threatening cases
- Prevention: Poloxalene (Bloat Guard®) 1-2 g/head/day, adequate roughage, ionophore support
- Forage particle size: >2.5 cm; overly fine roughage is not protective
8. Practical Feedlot Ration Examples
8.1 Adaptation-Phase Ration (300 kg feeder calf, Step 2)
| Feed Ingredient | Amount (kg DM/day) | Proportion (% DM) |
|---|---|---|
| Corn silage | 2.5 | 36 |
| Hay (grass or alfalfa) | 1.0 | 14 |
| Cracked barley | 2.0 | 29 |
| Soybean meal | 0.8 | 11 |
| Molasses | 0.2 | 3 |
| Vitamin-mineral premix | 0.15 | 2 |
| Sodium bicarbonate | 0.05 | 0.7 |
| TOTAL | ~7.0 kg DM |
NEm: ~1.60 Mcal/kg DM | CP: ~13.5% | NDF: ~32% | Concentrate: ~45%
8.2 Finishing-Phase Ration (450 kg feeder)
| Feed Ingredient | Amount (kg DM/day) | Proportion (% DM) |
|---|---|---|
| Cracked barley | 5.0 | 45 |
| Cracked corn | 2.0 | 18 |
| Corn silage | 1.5 | 14 |
| Chopped wheat straw | 0.5 | 5 |
| Soybean meal | 1.0 | 9 |
| Molasses | 0.3 | 3 |
| Vitamin-mineral premix | 0.20 | 2 |
| Sodium bicarbonate | 0.10 | 0.9 |
| Monensin premix | 0.03 | 0.3 |
| TOTAL | ~11.0 kg DM |
NEm: ~2.05 Mcal/kg DM | CP: ~12.5% | NDF: ~18% | Concentrate: ~80%
9. Feedlot Performance Monitoring Parameters
| Parameter | How It Is Measured | Target | Alarm Threshold | Frequency |
|---|---|---|---|---|
| ADG | Body weight checks every 14-28 days | 1.3-1.6 kg/day | <1.0 kg/day | Every 2-4 weeks |
| DMI | Bunk intake monitoring | 2.2-2.8% of body weight | 10%+ decline | Daily |
| FCR | DMI/ADG | 5.5-7.0 | >8.0 | Monthly calculation |
| Fecal score | Visual scoring (1-5 scale) | 3.0-3.5 | <2.5 (diarrhea) or >4.0 (constipation) | Daily observation |
| Morbidity rate | Sick animals / total group | <10% (adaptation), <3% (main feedlot phase) | >15% (adaptation), >5% (main phase) | Weekly |
| Mortality rate | Dead animals / total group | <1.5% (total feedlot period) | >2.0% | Cumulative |
| Liver abscess incidence | Slaughterhouse feedback | <10% | >20% | Each lot marketed |
10. Slaughter Timing and Optimal Days on Feed
Optimal slaughter timing is reached when marginal cost equals marginal revenue. As the feeding period continues, ADG declines, FCR worsens, and fat deposition rises. Beyond that point, the feedlot program becomes less economical (Owens et al., 1995).
| Animal Type | Starting Weight | Target Slaughter Weight | Optimal Days on Feed | Target Dressing Percentage |
|---|---|---|---|---|
| Beef-breed male | 250-300 kg | 550-650 kg | 180-240 days | 58-62% |
| Dual-purpose male | 250-300 kg | 500-600 kg | 200-270 days | 54-58% |
| Dairy-breed male (Holstein) | 200-250 kg | 500-550 kg | 270-330 days | 50-54% |
| Heifer | 200-250 kg | 400-480 kg | 180-240 days | 52-56% |
Practical Indicators for Slaughter Decisions
- Backfat thickness: 8-12 mm by ultrasound in beef breeds, 6-10 mm in dual-purpose cattle
- Ribeye area (REA): >75 cm² by ultrasound in beef breeds
- ADG trend: If ADG falls below 1.0 kg/day over the last 30 days, slaughter time should be considered
- FCR trend: If FCR rises above 8.0 during the last 30 days, the economic endpoint has likely been reached
- Market conditions: Live cattle and carcass price trends should also influence the decision
11. Water Management
Water is one of the most neglected yet performance-critical nutrients in feedlot cattle. Water restriction rapidly reduces both DMI and ADG. According to NASEM (2016), feedlot cattle commonly consume 3-5 times their daily dry matter intake in water.
Water Intake Targets
| Ambient Temperature | Water Intake (L/head/day) | Notes |
|---|---|---|
| <15°C | 25-35 | Winter conditions; monitor freezing risk |
| 15-25°C | 35-50 | Spring/autumn; generally ideal conditions |
| 25-35°C | 50-75 | Summer conditions; onset of heat stress |
| >35°C | 75-100+ | Severe heat stress; increase waterer capacity |
12. References
- Duff, G. C., & Galyean, M. L. (2007). Board-invited review: Recent advances in management of highly stressed, newly received feedlot cattle. Journal of Animal Science, 85(3), 823-840.
- Duffield, T. F., et al. (2012). Meta-analysis of the effects of monensin in beef cattle on feed efficiency, body weight gain, and dry matter intake. Journal of Animal Science, 90(12), 4583-4592.
- Galyean, M. L., et al. (2011). Board-invited review: Efficiency of converting feed to carcass weight in beef cattle. Journal of Animal Science, 89(12), 4116-4128.
- Klemesrud, M. J., et al. (2000). Metabolizable methionine and lysine requirements of growing cattle. Journal of Animal Science, 78(1), 199-206.
- Nagaraja, T. G., & Chengappa, M. M. (1998). Liver abscesses in feedlot cattle: A review. Journal of Animal Science, 76(1), 287-298.
- Nagaraja, T. G., & Lechtenberg, K. F. (2007). Acidosis in feedlot cattle. Veterinary Clinics of North America: Food Animal Practice, 23(2), 333-350.
- Nagaraja, T. G., & Titgemeyer, E. C. (2007). Ruminal acidosis in beef cattle: The current microbiological and nutritional outlook. Journal of Dairy Science, 90(E. Suppl.), E17-E38.
- NASEM (National Academies of Sciences, Engineering, and Medicine). (2016). Nutrient Requirements of Beef Cattle (8th rev. ed.). Washington, DC: The National Academies Press.
- NRC (National Research Council). (2000). Nutrient Requirements of Beef Cattle (7th rev. ed., update 2000). Washington, DC: National Academy Press.
- Owens, F. N., et al. (1995). Review of some aspects of growth and development of feedlot cattle. Journal of Animal Science, 73(10), 3152-3172.
- Owens, F. N., et al. (1997). The effect of grain source and grain processing on performance of feedlot cattle: A review. Journal of Animal Science, 75(3), 868-879.
- Owens, F. N., & Gardner, B. A. (2000). A review of the impact of feedlot management and nutrition on carcass measurements of feedlot cattle. Journal of Animal Science, 77(E-Suppl), 1-18.
- Zinn, R. A., et al. (2002). Feeding value of selected cereal grains for feedlot cattle. Journal of Animal Science, 80(10), 2592-2600.