Commercial broiler breeds look similar, but the differences in growth rate, feed efficiency, breast meat yield, and heat tolerance have real financial impact at the farm level. Most growers do not get to choose their breed — the integrator decides — but knowing what each breed is capable of helps you manage expectations, track performance, and have an informed conversation with your technical representative.
Head-to-Head Comparison Table
Sources: Cobb-Vantress Cobb500 Performance & Nutrition Supplement (2022); Aviagen Ross 308 Broiler Performance Objectives (2022). Targets are for mixed-sex birds under standard management conditions. Field results are typically 5–15% below these targets.
| Trait | Cobb 500 | Ross 308 | Notes |
|---|---|---|---|
| Day 14 live weight | 470 g (1.04 lb) | 485 g (1.07 lb) | Ross grows slightly faster early |
| Day 28 live weight | 1,620 g (3.57 lb) | 1,540 g (3.40 lb) | Cobb gains faster mid-cycle |
| Day 35 live weight | 2,190 g (4.83 lb) | 2,230 g (4.92 lb) | Ross slightly ahead at market weight |
| Day 42 live weight | 2,910 g (6.41 lb) | 2,950 g (6.50 lb) | Ross slightly heavier at heavy weight |
| FCR to 2.2 kg | 1.48–1.54 | 1.45–1.50 | Ross has a slight edge in early FCR |
| Cumulative FCR Day 35 | 1.53 | 1.50 | Ross converts slightly better early |
| Cumulative FCR Day 42 | 1.69 | 1.65 | Ross maintains slight edge |
| Breast meat yield (% carcass) | 23.5–25.0% | 22.5–24.0% | Cobb yields 1–1.5% more breast meat |
| Heat tolerance | High | Moderate | Cobb handles heat stress better |
| Dietary protein flexibility | High (tolerates 18–18.5% CP) | Moderate (needs higher CP) | Cobb allows lower-cost feed formulations |
Ross 308 vs Cobb 500: At a Glance
Use this quick decision matrix to match breed characteristics to your operational constraints:
| Factor | Choose Ross 308 If… | Choose Cobb 500 If… |
|---|---|---|
| Climate | Temperate, tunnel-ventilated houses | Tropical, hot, or seasonal regions |
| Feed cost priority | Standard feed formulations OK | Need lower-cost, lower-CP diets |
| Product focus | Whole bird or fast-food contracts | Breast meat deboning and value-added |
| Heat stress risk | Low to moderate | High — summer heat waves |
| Peak daily gain | 90–100 g/day at week 4–5 | 105 g/day at week 4–5 |
You Don't Choose, But You Should Know
In integrated poultry operations, the integrator selects the breed — not the grower. The integrator makes this decision based on processing plant capabilities, target market, and contract economics. Your role is to manage the breed you are given to its full potential.
Ask your integrator or technical rep these questions:
- Which breed and strain am I placing this cycle?
- What are the target weights at days 21, 28, 35, and 42 for this specific placement?
- At what FCR should I be concerned enough to call the hotline?
- What breast meat yield and processing window does the plant expect?
- Are there breed-specific management protocols I should follow (lighting, ventilation, feeding)?
Even if you don't choose, you should compare the actual performance of your flock against the breeder's published targets. If your flock consistently falls more than 10% below the targets for your breed, the cause is usually environmental, nutritional, or health-related — not the genetics.
Heavier Breeds: Cobb 700 and Ross 708
Both breeding companies offer heavier "sister lines" for markets that want larger birds:
| Breed | Target Weight | Age at Target | FCR Range | Best For |
|---|---|---|---|---|
| Cobb 700 | 6.0–7.0 lb (2.7–3.2 kg) | 42–49 days | 1.65–1.80 | Further processing, cut-up markets |
| Ross 708 | 6.0–7.0 lb (2.7–3.2 kg) | 42–49 days | 1.65–1.80 | Whole bird retail, portion control |
Heavier breeds produce fewer flocks per year but yield more meat per bird. The higher FCR is offset when breast meat premiums are high enough. Use the growth chart to track your specific breed's progress, and the FCR guide to monitor efficiency at heavier weights.
Genetic Trends and What They Mean for You
Broiler genetics improve at roughly 1% per year for growth rate and 0.5% per year for feed conversion. The breed you placed five years ago would grow faster and convert feed better today. This means:
- Review your protocols annually. Management programs developed for older genetics may be under- or over-performing.
- Track performance by flock and breed. Log actual weights, FCR, and mortality to see how your current placement compares to the breeder targets.
- Compare across houses. If one house consistently underperforms with the same breed, investigate house-specific factors (ventilation, lighting, equipment).
Tracking Breed Performance in Poultry Log
Each flock record in Poultry Log is tagged with the breed and placement date. When you log weekly sample weights, feed deliveries, and mortality, the system compares your flock's actual performance against the breeder targets for your specific breed and age. Drift alerts fire when actuals fall more than 10% below targets.
At closeout, your flock's performance feeds into the profitability dashboard, where you can see how growth rate and FCR affected margin. The budget template helps you forecast revenue based on projected breed performance, and the settlement calculator lets you verify your independent numbers against your integrator's sheet.
- Cobb-Vantress. Cobb500 Broiler Performance and Nutrition Supplement (2022). Download PDF
- Aviagen. Ross 308 Broiler Performance Objectives (2022). aviagen.com
- Poultria. Ross 308 vs Cobb 500 Management. poultria.com