Improving ADG in Broilers by Identifying Growth Constraints

Improving average daily gain (ADG) in broilers starts with understanding what is limiting growth, not simply increasing dietary nutrient density. Feed intake, nutrient utilization, environmental conditions and intestinal health can all influence performance. The challenge is identifying which constraints deserve attention before selecting an intervention.

ADG measures average body weight gain over a defined period, calculated as the change in average body weight divided by the number of days. Understanding why ADG falls below expectations requires looking beyond growth measurements alone.

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What factors most directly influence broiler ADG?

ADG depends on nutrient intake and how efficiently those nutrients support maintenance and tissue growth.

Feed intake is particularly important. In their review, Ferket and Gernat (2006) emphasized that management and flock-health challenges can affect consumption more substantially than dietary factors.

A flock receiving a properly formulated diet may still underperform if feed consumption is restricted. Conversely, birds maintaining expected intake but growing below target may face limitations involving digestibility, nutrient balance or health.

Evaluating ADG alongside feed intake and feed conversion ratio (FCR) helps distinguish these possibilities, although no single measure establishes the underlying cause.

How do environmental conditions restrict growth?

Broilers allocate nutrients and energy between growth, maintenance and physiological responses to environmental conditions.

Heat stress provides a well-documented example. A systematic review and meta-analysis of 12 studies by Liu et al. (2020) found that heat stress significantly reduced feed intake and body weight gain while increasing FCR and mortality.

These effects demonstrate why temperature, ventilation, air quality, stocking conditions and water availability should be evaluated alongside nutritional performance, particularly when growth differs between houses or production periods.

Can intestinal health limit growth without obvious disease?

Yes. Subclinical intestinal challenges can impair broiler performance without producing substantial mortality.

Emami and Dalloul (2021) reviewed the consequences of necrotic enteritis, highlighting how subclinical disease can reduce feed intake and weight gain while increasing FCR.

Intestinal inflammation and epithelial damage may compromise nutrient utilization, even when the formulated diet remains unchanged.

Feed represents one potential source of microbial exposure, but intestinal disease is multifactorial. Coccidial challenges, nutritional factors, environmental conditions and flock management also contribute.

Understanding how feed influences necrotic enteritis risk can help producers evaluate microbial quality within broader intestinal-health programs. Reducing feed contamination may help manage exposure but does not independently guarantee higher ADG.

Where does feed quality fit into the equation?

Nutritional formulation establishes the intended nutrient supply, but ingredient variability, processing conditions and physical feed deterioration can influence what birds ultimately consume.

In a controlled study, Lv et al. (2015) reported higher ADG and feed intake in broilers receiving crumble-pellet diets compared with mash diets.

Feed form is therefore one consideration when investigating growth limitations, alongside nutrient digestibility, ingredient quality and feeding-system performance.

The relationship between pellet quality and broiler performance warrants particular attention when physical feed deterioration may affect nutrient delivery.

How can producers identify what is limiting growth?

A practical investigation begins by comparing ADG against age- and strain-appropriate performance targets, then examining when growth begins to diverge.

Several performance patterns can help prioritize further investigation:

• Lower ADG with reduced feed intake: Investigate feed access, water delivery, environmental stress and feed palatability.

• Lower ADG with expected intake and worsening FCR: Examine nutrient digestibility, dietary balance and intestinal-health challenges.

• Growth differences between houses: Compare ventilation, temperature, stocking conditions and feeding-system performance.

• Growth shortfalls during specific production phases: Review dietary transitions, age-related nutritional requirements and disease pressure.

These patterns provide diagnostic starting points, not definitive explanations. Flock uniformity, mortality, feed-quality measurements and health observations should be evaluated together before attributing underperformance to a particular cause.

Improving ADG requires identifying what is holding growth back

Growth performance reflects the combined influence of nutrition, environment and flock health. The relative contribution of each can change throughout production.

Identifying where performance potential is being lost allows producers to prioritize interventions based on evidence rather than assumptions.

For operations investigating feed-quality limitations and microbial exposure, connect with an Anitox Clean Feed Expert to explore how feed hygiene can support broader broiler performance objectives.

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