Ross 308 Chicks – Weight Chart, Growth and FCR

Ross 308 is one of the most widely selected broiler strains used in chicken meat production. Farmers value it primarily for its rapid growth rate, efficient feed utilisation and ability to produce a uniform batch of broilers within a relatively short production cycle.

The term “Ross 308 breed” frequently appears in everyday searches. However, it is not entirely accurate. Ross 308 is a commercial broiler strain—a hybrid developed specifically for meat production. The Polish National Poultry Council – Chamber of Commerce lists Ross 308 in its register of commercial meat chicken strains alongside Cobb 500, among others.

Genetics alone, however, does not determine the final production result. The quality of day-old chicks, how quickly they begin drinking and feeding, house preparation, starter feed quality, gut health, ventilation and the ability to identify deviations from the production plan at an early stage are equally important.

What makes Ross 308 different?

Ross 308 is available in two variants. With the standard Ross 308 strain, chicks can be sexed at the hatchery based on the rate of feather development. Females feather more quickly, while males feather more slowly. In the Ross 308 FF variant, all chicks are fast-feathering.

This distinction is important, among other things, on farms that rear males and females separately. Males and females differ in their growth rates, feed intake and body weights achieved in subsequent weeks. For mixed-sex flocks, performance is assessed using the “as-hatched” table, which applies to chicks that have not been separated by sex.

Ross 308 – body weight, feed intake and FCR table

The values below are performance objectives for mixed-sex Ross 308 and Ross 308 FF flocks. They do not guarantee a specific result. Aviagen emphasises that achieving these parameters requires good management, appropriate environmental conditions and adequate nutrient levels. Raw material availability, climate, flock health and the production system may all cause actual results to differ from the table.

Broiler age	Target body weight	Cumulative feed intake	FCR
0 days	44 g	—	—
7 days	213 g	166 g	0.780
14 days	533 g	535 g	1.005
21 days	1,012 g	1,155 g	1.142
28 days	1,616 g	2,051 g	1.269
35 days	2,296 g	3,211 g	1.399
42 days	2,998 g	4,586 g	1.531
49 days	3,681 g	6,115 g	1.663
56 days	4,318 g	7,733 g	1.793

The data come from the official 2022 Ross 308/308 FF performance objectives. Body weight refers to the weight of a bird on the farm, including the contents of its digestive tract. Feed intake is calculated per live bird. The FCR provided by the breeder includes the chick’s initial body weight but does not account for mortality.

How should the Ross 308 table be interpreted?

The most common mistake is to monitor average body weight alone. A flock may achieve the target weight while consuming too much feed, showing poor uniformity or experiencing increased mortality. Such a result may appear satisfactory from a biological perspective but prove disappointing economically. At each weighing, at least four parameters should therefore be compared:

• average body weight,
• cumulative feed intake,
• water intake,
• mortality and culling.

The calculation methodology is also important. FCR calculated on the farm must be compared with previous production cycles using the same method. Otherwise, differences may result not from flock performance but from how initial body weight, mortality, feed remaining in the silo or the weight of culled birds are included in the calculation.

The first 24 hours after placement

For Ross 308 chicks, the first day is more than simply an adaptation period. It marks the beginning of the highly intensive development of the digestive tract, immune system and musculoskeletal system. If chicks take too long to find water or feed, compensating for these early losses can be costly and may not result in full flock uniformity.

After chick placement, farmers should assess not only air temperature but, above all, chick behaviour. Even distribution, calm vocalisation and active movement between feed and drinkers usually indicate that the conditions are appropriate. Chicks gathering under a heat source may indicate chilling. Moving away from radiant heaters, panting and drooping wings suggest overheating.

During the first two days, body temperature measured in the cloacal area can be a helpful parameter. The current Ross management handbook recommends a range of 39.4–40.5°C. Measurements should be taken from chicks collected from several parts of the brooding area rather than from a single location.

Crop-fill assessment

Crop fill shows what proportion of the flock has actually found feed and water. Merely observing a few chicks at a feeder is not sufficient.

Time after placement	Minimum proportion of chicks with full crops
2 hours	75%
4 hours	80%
8 hours	above 80%
12 hours	above 85%
24 hours	above 95%

The crop should be full, soft and rounded. A full but hard crop may indicate that the chick has consumed feed without having sufficient access to water. A high proportion of empty crops requires an immediate assessment of feeder placement, drinking-line pressure, temperature, lighting and chick activity.

Ross 308 body weight on day seven

Day seven is the first major checkpoint. According to the Ross nutrition guidelines, a chick’s body weight should be at least 4.5 times its initial weight by this point. For a chick weighing 44 g at placement, this corresponds to approximately 198 g. The official performance objective for a mixed-sex flock is even higher, at 213 g. If the average body weight on day seven is significantly below the target, farmers should not wait until the following week to take action. The first 24 hours, floor and litter temperatures, water intake, starter feed structure and feed availability in different parts of the poultry house should all be analysed. The average alone is not enough. An average result of 205 g may conceal a large group of birds weighing 170–180 g and a smaller group of considerably heavier broilers. For this reason, the coefficient of variation, or CV, should also be monitored during weighing. A high CV indicates that some birds are not benefiting equally from the available conditions.

Ross 308 nutrition

A feeding programme should not be determined solely by age. Target body weight, slaughter date, sex, the physical form of the feed, the composition of available raw materials and the flock’s health status must also be considered.

Starter feed

Starter feed should be provided for at least 10 days. If chicks do not achieve the expected body weight, this period can be extended. During the first few days, the digestive system changes exceptionally rapidly—the pancreas and intestines increase in size proportionally much faster than the body as a whole. The feed must therefore be highly digestible and well balanced. Reducing expenditure on starter feed often provides only apparent savings. Starter accounts for a relatively small proportion of total feed consumption, while the consequences of inadequate early nutrition can affect the remainder of the growing cycle.

Grower feed

Grower feed is generally provided from day 11 to day 24. Ross 308 broilers achieve very high daily weight gains during this period, making pellet quality and a smooth transition between feeds particularly important. An abrupt change in feed structure, smell or raw material composition may cause a temporary decrease in intake. Growth lost during the period of the most rapid development is more difficult to recover than a minor delay occurring at a later stage.

Finisher feed

Finisher feed is usually introduced after day 25. Finisher diets account for the largest share of total feeding costs, so their specifications should reflect the target body weight and how the birds will be sold. When producing broilers weighing more than 2.5 kg, more than one finisher diet may be required. There is no single feeding programme suitable for every farm.

Physical form of the feed

Even a well-balanced feed will not produce the expected results if birds are reluctant to consume it. Ross recommends good-quality crumble and pellets. A high proportion of particles smaller than 1 mm may negatively affect feed intake, body weight and FCR. Aviagen data indicate that reducing the proportion of these fine particles by as little as 10% can improve body weight and feed efficiency.

The problem does not always originate at the feed mill. Pellets may become damaged during transport, handling, operation of the feed conveyors and movement through the feeding system. Feed structure should therefore also be assessed in the feeders rather than solely on the basis of a sample taken from the silo.

Why does Ross 308 fail to achieve its target weight?

The cause is rarely limited to a single factor. The best starting point is to determine when the deviation first occurred.

Observation	What to check first
Low body weight as early as day 7	Crop fill, litter temperature, water intake and starter feed quality
Good weight on day 7, followed by poorer results after a feed change	Grower feed structure, proportion of fines, timing and method of feed transition
Good body weight but high FCR	Feed spillage, weighing accuracy, temperature and gut health
Significant variation among birds	Temperature distribution, number of feeding and drinking points and water pressure
Reduced intake after day 21	Ventilation, heat stress, stocking density, air quality and litter condition
Sudden change in water intake	Drinker operation, water temperature, flock health and feed composition

Fast-growing broilers generate large amounts of heat, particularly during the second half of the growing cycle. Aviagen indicates that maintaining an ambient temperature below 21°C after day 21 may improve the growth rate. However, this should not be treated as a fixed setting suitable for every poultry house. Bird behaviour, humidity, air speed and flock weight must be assessed together.

Assessing Ross 308 chicks upon delivery

The initial quality of a batch can be evaluated before the chicks are placed in the poultry house. This does not replace a veterinary examination, but it can reveal warning signs requiring more detailed inspection.

Good-quality chicks should be active, dry, respond appropriately to stimuli and quickly return to a natural position when placed on their backs. The navel should be closed and dry. The legs should be straight and free from injuries, swelling and noticeable discolouration.

Batch uniformity is also important. A large number of noticeably smaller chicks may indicate differences in parent flock age, incubation conditions or the time between hatching and delivery.

Upon delivery, the batch documentation, origin, vaccinations performed and transport conditions should also be checked. Traceability between the supplier and recipient is one of the fundamental elements of poultry production chain safety.

The vaccination programme should be developed with a veterinarian based on the status of the parent flocks, maternal antibody levels, the current epidemiological situation and the production technology used on the farm. It should not be copied automatically from another farm.

Ross 308 chicks from Veterinary Support

Good Ross 308 performance begins even before placement. Parent flock health, the incubation process, the quality of hatchery selection, vaccinations and transport conditions all play an important role.

Veterinary Support supplies day-old Ross 308 chicks, provides batch quality control, offers the option of protective vaccinations and arranges transport to farms throughout Poland. The company also provides specialist support from a poultry veterinarian, including disease prevention, biosecurity and the analysis of production problems. Learn more about our offer: day-old chicks and chickens.

Frequently asked questions about Ross 308