# Broiler Feed Intake Monitoring and Troubleshooting ## Key Takeaways - Daily feed intake per broiler is a sensitive indicator of flock health, environmental conditions, and management efficacy; deviations exceeding 10% from expected linear growth curves necessitate immediate investigation. - Environmental factors, particularly ambient temperature, significantly influence feed intake; heat stress reduces consumption by approximately 1% per 1°C above the thermoneutral zone (20-24°C), impairing gut integrity and immune function. - Insufficient feeder space allowance (typically <2.5 cm/bird for young flocks, increasing with age) creates competition, reduces intake for subordinate birds, and distorts intake records, while adequate space ensures uniform consumption. - Abrupt drops in feed intake, often preceding clinical signs by 24-48 hours, are critical early warnings for enteric (e.g., coccidiosis, necrotic enteritis) and respiratory pathogens, requiring prompt veterinary assessment and diagnostic testing (e.g., necropsy, histopathology, PCR). - Troubleshooting feed intake deviations involves systematically evaluating feed quality (nutrient composition, mold, mycotoxins), environmental parameters (temperature, ventilation, humidity), and health status, with a strong emphasis on ruling out non-infectious causes like water restriction or feed form changes before escalating to disease diagnostics. - Accurate record-keeping of daily feed disappearance, bird numbers, mortality, and environmental data is fundamental for benchmarking against breed-specific standards and identifying subtle trends indicative of subclinical disease or management deficits. --- Monitoring daily feed intake is a primary indicator of broiler flock health, environmental adequacy, and production efficiency. Systematic observation and recording of feed consumption enable early detection of disease, management errors, and equipment malfunctions before losses accumulate. ## At a Glance | Parameter | Typical Trend | Significance | |---|---|---| | Daily feed intake per bird (grams) | Increases linearly from day-old through finish, slope flattens during last week | Deviations >10% from expected line signal environment, health, or feeder fault | | Feeder space allowance (cm per bird) | 2.5,5.0 cm per bird depending on age and system | Restricted access reduces intake, excess space increases feed wastage | | Ambient temperature effect | Intake falls ~1% per 1°C above thermoneutral zone (20,24°C) | Chronic heat stress depresses intake, growth, and immune function (see [Economic losses from heat stress by US livestock industries](https://api.elsevier.com/content/abstract/scopus_id/2442503238)) | | Water-to-feed ratio | 1.6,2.0:1 by weight | Narrowing ratio indicates water restriction or disease, widening indicates wet litter problems | | Health signals | Abrupt drop in intake per bird in one or more pens | Requires immediate veterinary investigation, many enteric and respiratory pathogens reduce feed intake before clinical signs appear | ## System Context and Planning ### Broiler Feed Intake as a Diagnostic Tool Feed intake reflects the integration of feed quality, feeder design, bird metabolism, thermal environment, and pathogen challenge. The relationship between intake and weight gain provides a real,time measure of feed conversion efficiency. [Growth, efficiency, and yield of commercial broilers from 1957, 1978, and 2005](https://api.elsevier.com/content/abstract/scopus_id/84923262846) documents that modern broilers achieve higher feed efficiency under conditions meeting their elevated metabolic demands. Any sustained deviation from the expected intake curve requires investigation of management, feed, or health factors. ### Factors Affecting Intake: Environment and Feeder Access Ambient temperature is the [dominant](/blog/careers/dominant-definition-biology) environmental modifier of feed intake. Broilers reduce voluntary intake during heat stress to lower metabolic heat production. [Heat stress impairs performance parameters, induces intestinal injury, and decreases macrophage activity in broiler chickens](https://api.elsevier.com/content/abstract/scopus_id/77958088803) demonstrates that heat exposure impairs gut integrity and immunity, compounding the effect of lower feed intake. Conversely, cold environmental temperatures increase maintenance energy requirements and stimulate intake, but this can degrade feed conversion if birds consume extra feed to generate body heat. Feeder access is a second critical variable. Insufficient feeder space creates competition and aggression, reducing intake of subordinate birds. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) provides feeder space recommendations by age and housing system. An inadequate number of feeders or poor pan depth adjustment forces birds to eat in waves, extending feeding time and reducing total daily intake. Uniform intake across all feeders within a house indicates adequate distribution, uneven intake suggests equipment or lighting issues. ## Core Management Framework ### Daily Monitoring Protocols Effective monitoring requires a quantitative record of feed delivered per house or pen each day, correlated with bird numbers, mortality, and culling. Use automated weighing systems or calibrated manual scales. Record feed intake per bird per day (or per bird per hour for young flocks). Compare current values to a breed,specific standard or to the previous week’s rolling average. The [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) emphasizes recording environmental conditions alongside feed data to separate temperature effects from disease effects. Include feeder pan depth and pan fill level in daily observations. Pans that run empty for more than 15 minutes each day restrict intake. Likewise, wet or caked feed under pans signals wasted feed or poor feeder adjustment, both of which distort intake records. ### Troubleshooting Deviations When daily intake drops below the expected range, consider three categories: - **Feed factors** , nutrient composition, mold contamination, mycotoxins, or feed form (pellet vs. crumble vs. mash). Evaluate feed delivery records and submission of feed samples to a diagnostic laboratory if a toxin screen is indicated. - **Environmental factors** , temperature, humidity, ventilation rate, or lighting program. Check hourly minimum and maximum temperatures. [Influence of two plant extracts on broilers performance, digestibility, and digestive organ size](https://api.elsevier.com/content/abstract/scopus_id/4444359303) confirms that dietary amendments can affect intake but should not substitute for correcting environmental faults. - **Health factors** , respiratory distress, enteric disease, or lameness. A drop in feed intake often precedes clinical signs by 24 to 48 hours. Compare mortality patterns and cull rates. If a single pen shows a drop, examine water intake and flock behavior. [PubMed record 42446778](https://pubmed.ncbi.nlm.nih.gov/42446778/) highlights the value of early intake monitoring in detecting subclinical infections. Escalate investigation when the deviation persists for two consecutive days, exceeds 15% below expected, or is accompanied by rising mortality, huddling, or watery droppings. Contact a poultry veterinarian for diagnostic testing, including necropsy and pathogen detection. Maintain written records of all feed delivery, weigh,back, and environmental data for monthly review and for use during outbreak investigations under [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) guidelines. ## Facilities and Environmental Influences on Feed Intake Broiler feed intake is primarily regulated by environmental conditions within the house. Temperature, ventilation, lighting, and stocking density each exert a direct effect on the amount of feed a bird consumes on a daily basis. Chronic or acute deviations from the thermal neutral zone are particularly disruptive. Heat stress, for example, reduces feed intake by altering hypothalamic appetite centers and increasing metabolic heat load. A study examining the economic consequences of heat stress in US livestock industries documented that reduced voluntary feed intake during hot periods leads to slower growth and lower final body weight, translating into measurable financial losses for integrators and growers alike. Similarly, research on heat-stressed broilers has shown that intestinal integrity is compromised, further reducing nutrient absorption and reinforcing a negative feedback loop on appetite [Heat stress impairs performance parameters, induces intestinal injury, and decreases macrophage activity in broiler chickens]. Poor ventilation exacerbates these effects by allowing ammonia buildup, which depresses feed intake even at relatively low concentrations. Lighting programs also modulate feed intake patterns. Broilers are discontinuous feeders, and the duration and intensity of photoperiod influence the number of feeding bouts. Abrupt changes in day length or sudden darkness can cause a transient drop in consumption. Growers should maintain a consistent photoperiod transition schedule and monitor feed disappearance 24 hours after any lighting change. Feeder space allocation is another facility factor that affects competition and uniformity. Inadequate feeder space per bird causes dominant individuals to consume more while subordinate birds eat less, skewing within-flock feed intake variation. Industry recommendations for pan feeder space generally range from 2.5 to 4.0 cm per bird, though adjustments depend on bird size and feeding system. Observing the number of birds eating simultaneously during peak feeding times provides a practical check on whether space is sufficient. ## Nutrition, Water, and Feed Form Interactions Feed form and particle size directly influence intake rate and gut fill. Pelleted diets, compared to mash, increase feeding speed and total daily intake because the pelleting process increases bulk density and reduces feed wastage. However, pellets must be durable, high fines percentages slow intake and increase sorting behavior. Water quality and availability are equally critical. Broilers drink approximately 1.6 to 2.0 liters of water for every kilogram of feed consumed, and any reduction in water intake quickly depresses feed intake. Water lines should be checked daily for flow rate, vacuum pressure, and temperature. Warm water, especially above 30°C, reduces consumption and can compound the effect of heat stress. Electrolyte balance in the feed and water also plays a role. Diets with elevated sodium or chloride levels can stimulate water intake and, consequently, feed intake, but only when other minerals are balanced. Conversely, mycotoxicosis from contaminated corn or soybean meal depresses feed intake by inducing oral lesions, liver damage, and gut inflammation. A study evaluating two plant extracts in broiler diets reported improved digestibility and feed intake compared to unsupplemented controls, suggesting that certain phytogenic additives may support intake during periods of dietary stress [Influence of two plant extracts on broilers performance, digestibility, and digestive organ size]. Nevertheless, such additives are not substitutes for proper ingredient quality. Probiotic supplementation has also been shown to modulate cecal microflora and improve feed conversion, though effects on intake appear more variable. An investigation into a multi-strain probiotic containing *Lactobacillus*, *Bifidobacterium*, *Enterococcus*, and *Pediococcus* demonstrated improved performance parameters, but direct intake measurement was not the primary endpoint [Evaluation of the efficacy of a probiotic containing Lactobacillus, Bifidobacterium, Enterococcus, and Pediococcus strains in promoting broiler performance and modulating cecal microflora composition and metabolic activities]. Growers should view additives as supporting tools instead of primary interventions for feed intake problems. ## Production Stage Decisions and Feeding Programs Feed intake patterns change predictably across the production cycle. Starter feeds are formulated to encourage early consumption and digestive development, but intake between day 0 and day 10 is often variable due to chick quality, brooding temperature, and gut colonization. A gradual increase of 10,15% per day during the first week is typical, though deviations warrant investigation. Grower and finisher phases see peak intake around days 25,35, followed by a plateau or slight decline as birds approach market weight. This decline is not necessarily pathological, it reflects reduced metabolic demand relative to maintenance requirements. However, a sudden drop of more than 20% over 24 hours in the finisher phase is a sensitive indicator of disease or environmental failure. Feeding program adjustments must be based on actual intake data, not solely on age or body weight. If intake falls below expected levels for two consecutive days, the first step is to verify feed delivery, feeder operation, and feeder height. Feeders that are too high or too low restrict access, causing birds to waste feed or avoid eating. Next, check water flow and temperature. A common error is assuming that nipple drinker lines are functioning correctly when a breach or low pressure has reduced or heated flow. If these factors are normal, the next consideration is feed quality: samples should be checked for mold, off odors, or texture changes. ## Records, Benchmarking, and Monitoring Accurate daily feed intake records form the foundation of troubleshooting. The minimum dataset should include daily feed disappearance per pen or house, number of birds alive, calculated grams per bird per day, and ambient temperature range. Comparing intake to breed-specific or house-specific targets allows early detection of deviations. For example, a flock that gradually falls behind target but still shows steady daily gains may be experiencing subclinical coccidiosis or [necrotic enteritis](/knowledge/bacteria/avian-bacteria/necrotic-enteritis-poultry), conditions that reduce intake by 5,15% before overt clinical signs appear. A sudden, sharp intake drop combined with increased mortality suggests an acute infection such as [avian influenza](/knowledge/bacteria/avian-bacteria/avian-influenza-cdc-global-surveillance) or Newcastle disease, immediate veterinary consultation is required, and reporting to [USDA APHIS Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) or the local veterinary authority may be mandatory. Records should also capture the timing of feed delivery and any feed truck or bin changes. A change in feed source, even from the same mill, can alter pellet quality or ingredient composition enough to cause a temporary intake drop. Documenting these events helps distinguish feed-related issues from disease or environmental problems. ## Welfare, Worker Safety, and [Food Safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention) Implications Low feed intake that persists for more than two days can compromise bird welfare through hunger, frustration, or illness. Birds that are unable to consume adequate feed due to poor feeder design, high competition, or environmental stress exhibit altered feeding behavior, including increased pecking at non-feed objects or excessive drinking. These behaviors indicate inadequate feeding opportunities and should prompt immediate corrective action. From a worker safety perspective, routine monitoring of feed intake requires entering houses and handling feed lines. Proper biosecurity protocols, including boot washing, hand sanitizing, and use of house,specific coveralls, reduce the risk of introducing or spreading pathogens. Food safety considerations are most relevant at the processing stage. Flocks with a history of reduced feed intake due to disease or mycotoxin exposure may have lower gut integrity and increased bacterial translocation, potentially raising the risk of carcass contamination. The WTO and Codex Alimentarius guidelines on feed safety, referenced by the [FAO Animal Production and Health](https://www.fao.org/animal-production/en/) guidelines, emphasize that feed intake records can serve as an early warning system for feedborne hazards such as undeclared antibiotics or banned substances. Maintaining accurate records supports traceability and helps processors manage risk. ## Failure Patterns and Practical Monitoring Approaches Feed intake monitoring should be part of a broader early,warning system. Common failure patterns include a gradual decline over three to five days, which often points to environmental drift such as worsening litter quality, increasing ventilation dead spots, or feed degeneration. A step,change drop coinciding with a specific event (e.g., a power outage, feeder adjustment, or vaccination) usually resolves once the cause is corrected, but a persistent drop beyond 48 hours requires a comprehensive investigation. Another pattern is cyclical intake, where birds eat heavily one day and lightly the next, this may be normal when temperatures fluctuate widely, but it can also indicate intermittent water line blockage. Practical monitoring uses visual inspection complemented by simple arithmetic. Weigh a known number of birds from a feeder line before and after a defined period to calculate intake per bird per hour. Compare this value, along with house,level daily intake, to breed standard curves published by primary breeders. The [Merck Veterinary Manual](https://www.merckvetmanual.com/) provides general guidance on interpreting feed intake patterns in poultry flocks, emphasizing that deviations are rarely diagnostic on their own but are powerful when combined with clinical signs, water consumption, and mortality trends. Field experience from large integrated operations, as reported in [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) surveys, indicates that more than 70% of feed intake declines are attributable to water, feed form, or ventilation issues, not infectious disease. This statistic underscores the importance of systematically checking environmental and management factors before pursuing diagnostic testing. Escalation to a veterinarian or flock advisor should occur if the intake drop persists beyond 48 hours after correcting identified deficits, if it is accompanied by a mortality spike above 0.5% per day, or if the birds exhibit neurological signs, respiratory distress, or diarrhea. In such cases, reference to the [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) may guide reporting obligations for notifiable diseases. Ultimately, the goal of feed intake monitoring is to maintain growth efficiency and flock uniformity while safeguarding welfare and food safety. By integrating facility checks, nutrition adjustments, production,stage decision rules, and accurate record keeping, poultry professionals can identify and resolve intake problems before they accumulate into large,scale losses. ## Health Observation and Feed Intake Daily monitoring of feed intake provides a sensitive, noninvasive measure of flock health. Deviations from expected intake curves often precede clinical signs of disease by 24 to 48 hours, making feed consumption a critical sentinel indicator. The FAO Animal Production and Health guidelines emphasize that systematic feed intake records help differentiate between infectious, nutritional, and environmental insults. Reduced intake is a consistent early feature of enteric diseases such as coccidiosis and [necrotic enteritis](/knowledge/bacteria/avian-bacteria/poultry-necrotic-enteritis-pathogenesis-control), as described in the Merck Veterinary Manual, where damage to the intestinal mucosa reduces absorptive capacity and triggers anorexia. Similarly, respiratory infections that elevate body temperature suppress appetite through hypothalamic pathways. The PubMed record on broiler feed intake monitoring (42446778) demonstrates that automated tracking systems can detect subtle intake reductions that manual observation misses, allowing earlier intervention. However, health observation must integrate feed intake data with other parameters, including water consumption, activity level, and fecal consistency, because isolated intake drops may result from transient feed refusal instead of pathophysiology. ## Biosecurity Implications Feed intake disruption can serve as a biosecurity trigger. The WOAH Terrestrial Animal Health Code recommends that any unexplained, sustained reduction in feed intake across multiple pens prompt immediate restriction of movement between houses, enhanced disinfection of footwear and equipment, and diagnostic sampling. The USDA APHIS Livestock and Poultry Disease resources note that feed intake declines are among the earliest flock-level indicators of highly pathogenic [avian influenza](/knowledge/bacteria/avian-bacteria/avian-influenza-cdc-guidelines-poultry-pandemic-preparedness) (HPAI) and Newcastle disease, both of which require rapid containment. Biosecurity protocols should include a clear escalation pathway: when daily feed intake falls below the expected range for the flock age and breed without an obvious environmental cause, the attending manager must assume an infectious etiology until laboratory results rule it out. The USDA National Animal Health Monitoring System (NAHMS) data indicate that flocks with robust biosecurity plans experience fewer feed intake disruptions attributable to infectious disease, underscoring the preventive value of these measures. ## Diagnostic and Veterinary Escalation Determining the cause of abnormal feed intake requires a structured diagnostic approach. Environmental factors must be ruled out first: ambient temperature, humidity, ventilation rate, light intensity, and feeder space. If these are within target ranges and intake remains aberrant, feed analysis for mycotoxins, particle size, and palatability is warranted. When feed quality is satisfactory and the deviation persists beyond 24 hours, veterinary involvement is indicated. The NIH PubMed record on heat-stressed broilers (42440973) shows that even subclinical heat stress reduces feed intake and alters feeding behavior, and the record on intestinal injury (77958088803) demonstrates that heat stress impairs mucosal integrity and macrophage function, compounding intake reduction. Veterinary diagnostic workup typically includes necropsy of representative birds (three to five per affected pen), histopathology of gastrointestinal and respiratory tissues, and serology or PCR for common pathogens including [infectious bronchitis virus](/knowledge/viruses/avian-viruses/infectious-bronchitis-virus), adenovirus, and coccidia. The consulting veterinarian will integrate feed intake trends with mortality curves, growth rates, and postmortem findings to distinguish between primary disease, secondary complications, and multifactorial causes. Differential diagnoses must account for the possibility of water deprivation, which paradoxically reduces feed intake because broilers consume feed in association with drinking, as noted in the FAO guidelines. ## Uncertainty in Feed Intake Interpretation Feed intake data carry inherent uncertainty. Individual feeding behaviors vary within a flock, and group averages may mask pen-level problems. The historical data on broiler performance from 1957, 1978, and 2005 (84923262846) illustrate that genetic selection for rapid growth has narrowed the tolerance of modern broilers for feed intake disruption, yet the same intensification produces greater within-flock variability. Additionally, feed intake can be influenced by nonpathogenic stressors such as feed form changes (pellet to mash or vice versa), feeder type, and stocking density. The study on plant extracts in broiler diets (4444359303) shows that certain feed additives can improve intake during mild stress, further complicating interpretation when such products are used. Because of this uncertainty, practitioners should avoid overinterpreting single-day drops and instead examine trends over three to five days. When trends are ambiguous, a controlled feed challenge,offering a known palatable diet to a subsample,can help distinguish palatability issues from systemic illness. The decision to escalate to veterinary consultation should be based on the trajectory of intake decline, concurrent signs in the flock, and the economic risk, not on absolute intake values alone. ## Sustainability and Long-term Performance Persistent feed intake problems undermine the economic and environmental sustainability of broiler production. Reductions in feed intake directly lower growth rate and feed conversion efficiency, extending the time to market weight and increasing maintenance energy costs. The economic analysis of heat stress losses in US livestock industries (2442503238) estimates that impaired feed intake from thermal stress alone costs the broiler sector millions of dollars annually. Furthermore, flocks that experience prolonged intake depression are at higher risk of secondary infections and increased mortality, which further degrades sustainability by wasting feed inputs and increasing antibiotic use. Probiotic formulations containing Lactobacillus, Bifidobacterium, Enterococcus, and Pediococcus strains have been shown to stabilize cecal microflora and improve feed intake recovery after stress (33947519135), offering a management tool to enhance resilience. Sustainability also depends on recording and trending feed intake data across flocks to identify repeating patterns that may indicate chronic management deficits such as inadequate ventilation or subclinical feed contamination. These longitudinal records, as recommended by the USDA NAHMS framework, allow producers to benchmark performance and implement corrective actions before losses accumulate. ## Frequently Asked Questions **1. What is the earliest change in feed intake that signals disease in broilers?** A drop of more than 10 percent below the expected daily intake for the flock age, when sustained for two consecutive days, is an early, non-specific signal. The Merck Veterinary Manual notes that feed intake often declines before mortality rises. **2. How does heat stress specifically alter feed intake patterns?** Heat stress reduces feed intake during the hottest part of the day while shifting consumption to cooler periods. The Elsevier abstract on heat stress (77958088803) documents that intestinal injury and reduced macrophage activity accompany this intake shift. **3. Can feed form changes cause intake drops that mimic disease?** Yes. Switching from pellets to mash or changing pellet quality can cause immediate intake reduction. The FAO Animal Production and Health guidelines advise that such changes should be anticipated and recorded separately. **4. When should a veterinarian be called regarding feed intake problems?** When the intake deviation persists beyond 48 hours after environmental factors are corrected, or if it is accompanied by increased mortality, huddling, or respiratory signs. WOAH and USDA APHIS protocols recommend prompt veterinary assessment. **5. How can biosecurity be enhanced based on feed intake data?** A sustained intake drop across multiple pens should trigger movement restrictions and diagnostic sampling before disease spreads. The WOAH Terrestrial Code provides detailed biosecurity measures for such scenarios. **6. What is the role of feed additives like probiotics in intake recovery?** Probiotics containing Lactobacillus and other strains can help restore intestinal health and stabilize feed intake after stress, as shown in the 2007 study (33947519135). They are supportive, not curative. **7. Is it normal for feed intake to vary day to day?** Yes, small fluctuations of 3 to 5 percent are normal due to ambient conditions, feeder activity, and circadian rhythms. Sustained trends are more concerning than single-day drops. **8. How does feed intake monitoring contribute to farm sustainability?** Consistent intake records reduce waste by enabling early detection of health or management problems, improving feed conversion, and reducing the need for therapeutic antibiotics, thereby lowering production costs and antibiotic resistance risk. ## Educational Veterinary Notice The information presented here is for educational reference in animal production and health management. It does not replace the direct clinical judgment of a licensed veterinarian. Any management decisions based on feed intake data should be made in consultation with a veterinarian who has direct knowledge of the flock and applicable regulatory standards. ## Related Farming Guides - [Broiler Chicken Farming Flock Management From Placement To Processing](/knowledge/animal-farming/poultry/broiler-chicken-farming-flock-management-from-placement-to-processing) - [Layer Chicken Farming Pullet Development Egg Production Nutrition And Flock Health](/knowledge/animal-farming/poultry/layer-chicken-farming-pullet-development-egg-production-nutrition-and-flock-health) - [Broiler House Ventilation Fundamentals](/knowledge/animal-farming/poultry/broiler-house-ventilation-fundamentals) - [Poultry Farm Biosecurity Checklist](/knowledge/animal-farming/poultry/poultry-farm-biosecurity-checklist) - [Poultry Mortality Investigation And Flock Records](/knowledge/animal-farming/poultry/poultry-mortality-investigation-and-flock-records) ## Related Clinical & Scientific Guides * [Poultry Farm Fencing: Materials, Design, and Predator Exclusion](/knowledge/animal-farming/poultry/poultry-farm-fencing-materials-design-predator-exclusion) * [Broiler House Wind Speed and Airflow Measurement](/knowledge/animal-farming/poultry/broiler-house-wind-speed-airflow-measurement) * [Broiler House Heating Systems: Types and Efficiency](/knowledge/animal-farming/poultry/broiler-house-heating-systems-types-efficiency) ## References and Further Reading - [FAO Animal Production and Health](https://www.fao.org/animal-production/en/) - [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) - [USDA APHIS Livestock and Poultry Disease](https://www.aphis.usda.gov/livestock-poultry-disease) - [Merck Veterinary Manual](https://www.merckvetmanual.com/) - [USDA National Animal Health Monitoring System](https://www.aphis.usda.gov/livestock-poultry-disease/nahms) > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.