Broiler live weight and daily gain by age (table)
We give indicative live weight and daily weight gain (how many grams the bird puts on in a single day) for broilers week by week. The figures are indicative and based on Aviagen guidelines for the Ross 308 line. We also explain how to compare your flock against the standard and what to do when birds fall off the growth curve.
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A broiler (broiler chicken) is a bird raised solely for meat — it grows fast and over a short period. A live weight and daily gain table lets you track in real time whether your flock is "holding the curve" (growing in line with the standard) or falling behind. This is part of the broiler guide cluster — the full picture of the production cycle is in the guide on the broiler production cycle step by step and the main guide on broiler farming.
What is daily weight gain?
Daily weight gain is the number of grams a bird puts on in a single day. You calculate it simply: today's weight minus yesterday's weight. Early in the rearing cycle the daily gain is small (about 20 g), because the bird is still very small. In the middle of the cycle (around weeks 4–5) the daily gain is at its highest — this is when broilers grow fastest, putting on about 90–100 g a day. Towards the end of the cycle the gain starts to fall, but FCR (feed consumed per kilogram of weight gain — covered in the broiler FCR calculator) rises markedly.
Where do the numbers in this table come from?
All values are indicative and based on the Aviagen document "Ross 308 Broiler: Performance Objectives" (2022 edition). The values refer to a mixed group of birds (average of males and females). Males (cockerels) grow faster and are heavier than females (pullets) — the difference can be about 10–15% in favour of males. Results on your farm may differ depending on the bird line, feeds, temperature, stocking density and many other factors. Treat the table as a reference point, not a rigid rule. More about nutrition at each phase in the guide on broiler feeding phases — table.
Indicative broiler live weight and daily gain — week by week
Indicative values per Aviagen Ross 308 Performance Objectives 2022*. Average for males and females — males are heavier. Adjust to your bird line and farm conditions.
Day 7 — about 190 g
In the first week the bird starts from hatch weight (about 40–45 g) and grows slowly — daily gain is about 20 g per day. At this stage, flock uniformity matters more than the absolute weight — birds should be similar in size. Monitor weight by weighing a random sample (for example 1–2% of the flock). Details of the first days are in the guide on broiler live weight on day 7.
Day 14 — about 470 g
Daily gain rises to about 40 g per day. The bird is noticeably larger than at placement, but still small. This is an important moment for feed and water access — overcrowding at drinkers and feeders slows growth. Check that temperature and ventilation are correct — heat stress at this age quickly hits weight gain.
Day 21 — about 940 g
Daily gain approaches about 65 g per day. This is a turning point: the bird is approaching 1 kg and starts consuming far more feed than in the first weeks. If flock weight is clearly below about 900 g, it is worth checking feed (quality, access), temperature, and flock health (mortality, coughing, diarrhoea).
Day 28 — about 1,540 g
Daily gain reaches about 85 g per day. Week four is one of the most important growth phases — the bird grows very fast and needs plenty of feed and water. FCR starts to matter — feed consumed per kilogram of gain is rising. Males are already noticeably heavier than females at this age. Monitor flock composition if rearing males and females together.
Day 35 — about 2,230 g
Daily gain reaches its peak: about 90–100 g per day. Broilers are growing fastest. At the same time, heat production by the flock rises — high stocking density can push house temperature up. Watch ventilation and welfare closely. At this point you decide whether birds go to slaughter in a week or stay longer (higher FCR, but greater live weight).
Day 42 — about 2,950 g
Daily gain drops to about 80–85 g per day, though the bird is still growing. FCR is now noticeably higher than in the middle of the cycle — the bird uses proportionally more feed for each additional kilogram. This is the typical slaughter age for most broiler farms in Poland. Beyond day 42, further rearing is possible but profitability falls. Details of cycle economics are in the guide on the broiler production cycle.
How to recognise when a flock is "falling off the curve"
A downward deviation of more than about 10% below the target weight is a signal worth investigating — it does not always mean a serious problem, but it calls for a response.
Weight below target — check the feed
The most common cause of lower-than-expected weight is limited access to feed or water, or poor feed quality. Check: are feeders and drinkers full and accessible to all birds; is the feed damp or old; does the feeding programme match the bird age (phases: starter, grower, finisher)? More about feeding phases in the guide on broiler feeding phases.
Weight below target — check temperature
Too low a temperature in the early weeks means the bird uses energy keeping warm instead of growing. Too high a temperature (heat stress) means the bird eats less and grows more slowly. In both cases daily gains fall below the standard. House temperature in the first weeks should be about 32–34°C (at floor level), stepping down gradually in subsequent weeks.
Low flock uniformity — large size differences between birds
If when you weigh a random sample you see very large differences (some birds twice the weight of others of the same age), there is a uniformity problem. Causes: unequal access to feed and water, disease early in the rearing cycle, uneven conditions in different parts of the house. Low uniformity leads to poorer slaughter results and makes planning harder.
Higher mortality alongside poor weight gain
Mortality above normal combined with low live weight may indicate disease (for example respiratory infection, coccidiosis) or a serious environmental problem (ammonia, poor ventilation). In this case call a veterinarian. Mortality benchmarks depend on age and conditions — as a rough guide, total mortality over the whole cycle in a well-managed farm should not exceed about 3–4%.
Frequently asked questions about broiler live weight and daily gain
How much should a broiler weigh on day 7?add
Indicatively about 190 g per Aviagen Ross 308 guidelines. This is an average for a mixed male-and-female group. If your birds are noticeably lighter (for example below 160–170 g), check house temperature (it should be about 32–34°C at floor level), access to water and feed, and the quality of chicks at placement. More detail in the guide on broiler live weight on day 7.
When do broilers grow fastest?add
Daily gain is highest around weeks 4–5 — at that stage a bird can put on about 90–100 g per day. After days 35–42 the daily gain starts to fall and FCR (feed per kilogram of gain) rises. That is why most Polish farms send birds to slaughter around day 42 — it is the trade-off between live weight and feed efficiency.
Why are males (cockerels) heavier than females (pullets)?add
Male broilers grow faster and have a different body composition than females. At slaughter on day 42, males can be about 10–15% heavier. Some farms run sex-separate rearing to better tailor conditions and slaughter timing to each sex. The table gives values averaged across both sexes.
What should I do if my birds weigh less than the table says?add
First check how large the deviation is. Up to about 5–10% below the standard is usually normal variability between farms and bird lines. More than 10% below the standard is worth checking: access to feed and water, temperature and ventilation, flock health (mortality, bird appearance, droppings), and chick quality at placement. If you cannot find an obvious cause or the situation repeats, consult a veterinarian or a nutrition adviser.
What is FCR and how does it relate to live weight?add
FCR (Feed Conversion Ratio) is a measure of feeding efficiency — how many kilograms of feed you need to supply for the bird to gain one kilogram of live weight. The lower the FCR, the better. FCR rises with bird age — it is low early on (about 1.2–1.3) and can exceed 1.8–2.0 towards the end of the cycle. This is one reason why keeping birds significantly beyond the planned slaughter date is not worthwhile. Details and a calculator in the guide on broiler FCR — how to calculate it.
How do I weigh birds in the house to check flock weight?add
Weigh a random sample — at least 1–2% of the flock, but no fewer than 30–50 birds from different parts of the house. Catch birds at various times of day to avoid bias (in the morning they have fuller crops after drinking). Weigh each bird individually and calculate the average. Compare against the table standard. Repeat weekly or every few days at critical points in the cycle (for example around days 7, 14, 21 and 28).
Sources & resources
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