Ontario Animal Health Network (OAHN)
Poultry Expert Network
Quarterly Producer Report

An overview of the Anatomy, Physiology and Behaviour of Heat Stress in Poultry

Dr. Emily Martin, Animal Health Laboratory, University of Guelph

Raising poultry in warm weather creates challenges for temperature regulation of barns to keep birds comfortable. Understanding how birds respond to increased temperature could help to interpret behaviour and detect when birds are uncomfortable.

Birds have a higher normal body temperature than mammals with a range of 40.5°C to 41.5°C. This temperature can be increased by 1-2°C but there is a limit before birds become hyperthermic (over heat). There are multiple interrelated factors including activity, feeding, basal metabolic rate and thermal requirements that interact with physical and biochemical changes allowing birds to maintain homeostasis and thermoregulation. Response to heat stress can vary depending on whether it is acute (very short duration, hours/a few days) or chronic (several days/weeks); however, the main changes are similar.

Between 30°C and 33°C (ambient temperature), the body temperature starts to increase. The peripheral tissues heat and then this heat is transferred to the core body temperature. This heat can be transferred to the environment if the ambient temperature is lower than body temperature. It takes 3-5 days for adult chickens to acclimatize to ambient temperature change. Birds that are acclimatized gradually are more resilient than those experiencing a sudden increase in temperature. Birds do not have sweat glands, but they have several other ways to release body heat.

Anatomic adaptations:

• Legs and feet: There are shunts between veins and arteries to allow heat exchange and heat loss from uninsulated (unfeathered) areas of the body.
• Behind the eyes: There is a vascular heat exchanger between the optic cavity and brain. This allows dissipation of heat through the cornea, eye, buccal cavity, beak and nasal passages.
• Comb and wattles: There is dilation of peripheral blood vessels allowing transfer of heat to the environment.

Physiologic adaptations: Respiration and pH

• Panting:
  • Loss of heat by evaporative cooling from surfaces of the mouth and respiratory system. Birds start to pant when body temperature reaches 42°C. It is thought that hens reach their maximum ability to lose heat through evaporation at an ambient temperature of 32°C and RH of 50-60%.
  • Increased loss of CO2 from lungs followed by decreased bicarbonate in blood results in a rise of plasma pH resulting in respiratory alkalosis. This depends on the degree and length of thermal stress, as well as acclimatization. To balance pH, the kidneys excrete bicarbonate and retain hydrogen ions leading to metabolic acidosis. When acid-base balance is altered this results in poor production performance.
    • Laying hens: Loss of bicarbonate affects eggshell formation due to limiting availability of the anion needed for formation of CaCO3 (calcium carbonate) crystals in the shell.
• Heart: The circulatory system contributes significantly to heat dissipation by moving heat from the core body to the peripheral tissues as well as altering O2 supply.

There are 5 mechanisms used to maintain body temperature: excretion, evaporation, convection, conduction and radiation. Bird behaviour is modified in order use the above mechanisms as well as anatomic and physiologic adaptations:

• Less time walking/standing/socializing, changing posture, extend neck while standing
• Increase distance from other birds (increase heat loss by radiation)
• Droop and hold wings out from body (increase heat loss by convection – air movement)
• Consume more water (immediate response, to compensate for evaporative cooling) leads to increased excretion
• Consume less feed (delayed response – hours, decreases metabolic heat)
• Splash water on combs and wattles (increase evaporative cooling)
• Reduce egg production
• Will seek shade or select a microenvironment to avoid environmental extremes
• Panting (increase evaporative cooling)
• Gular flutter: Rapid vibration of upper throat passages not involved in gas exchange (nasal cavities, nasopharynx, larynx, trachea). Driven by the hyoid apparatus and is used as an attempt to reduce respiratory alkalosis in heat stressed birds.

When coping with heat stress, thermoregulation competes with multiple systems for energy. There are adverse effects on intestinal integrity and permeability allowing pathogen entry. The immune system is weakened causing increased susceptibility to infections. Energy is not directed to reproductive organs resulting in infertility. Production parameters are altered including decreased feed intake, decreased body weight gain, decreased egg production/quality (decreased shell weight), and increased feed conversion ratio. Meat quality is compromised as increased ambient temperature results in meat having decreased protein content, increased fat content (breast, thigh and drumstick), and other quality issues.

General management strategies revolve around housing and nutrition.

• Housing: Decrease stocking density, housing design, ventilation, cooling systems.
• Nutrition: Cool water, modified feeding times, electrolytes, feed supplements (vitamins, minerals), other additives (probiotics, bioactive compounds).

Being able to identify the physical signs of heat stress and understanding the various ways heat can be shed by birds can support decisions on barn management to mitigate heat stress. Talk to your veterinarian about your particular situation to plan for heat stress management.

References:

Etches, R. J. et al. Chapter 4: Behavioural, Physiological, Neuroendocrine and Molecular Responses to Heat Stress. In: Poultry Production in Hot Climates. 2nd edition. N.J. Daghir, ed. CAB International 2008:48-79.

DEFRA: Heat Stress in Poultry – Solving the Problem https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69373/pb10543-heat-stress-050330.pdf

Goel, Akshat. Review: Heat stress management in poultry. J Anim Physiol Anim Nutr. 2021;105:1136–1145

Ullah Khan, Rifat, et al. (2021) Physiological dynamics in broiler chickens under heat stress and possible mitigation strategies, Animal Biotechnology,

DOI: 10.1080/10495398.2021.1972005

Poultry Veterinarian Survey Highlights – Q2 2022

Broilers

The ILT in a commercial broiler flock from December is resolved.  

Early systemic bacterial infections (<14 days) were generally stable with an equal number of practitioners indicating decreased or increased cases this quarter. Escherichia coli in combination with Enterococcus cecorum and Clostridium perfringens were identified by practitioners. Salmonella isolations were reported as stable to decreased. The AHL reported confirmed cases due to mixed infection of E. coli with or without E. cecorum.

Other causes of early mortality (<14 days) were generally stable with an equal number of practitioners indicating decreased or increased cases this quarter. AHL identified a case of mycotic pneumonia and a case of myocarditis.

Late systemic bacterial infections (>14 days) were reported as stable to slightly increased by practitioners. E. coli and Enterococcus cecorum were the main bacteria reported. AHL reported stable numbers of cases attributed to either E.coli and/or E. cecorum, or both in combination with G.anatis, C. perfringens, or S. Typhimurium. Practitioners reported 0-46% of E. coli isolates have been resistant to Trimethoprim sulfa (TMS).

1. C. perfringens was identified again in late bacterial infections after not being detected in either early or late bacterial infections in the last quarter (Q1 2022).

The number of cases of nutritional and developmental lameness were reported as stable by the responders. Rickets (calcium or vitamin D deficiency), tibial dyschondroplasia and overheating were noted as a diagnoses by practitioners. AHL also reported 3 cases of tibial dyschondroplasia.

Bacterial lameness was reported as stable to slightly increased for this quarter and was attributed to E. coli and E. cecorum, alone or in combination with S. aureus. AHL reported decreased cases of bacterial lameness. E.coli was isolated from one case, otherwise, tenosynovitis was diagnosed on histopathology.

Viral associated lameness (reovirus) cases were reported as stable to decreased. AHL reported a decrease in confirmed and suspect cases for a second quarter as well as fewer strains being identified. Only SK_R38 and SK_R12 were identified.

Infectious bursal disease virus (IBDV) infections were reported as generally stable with an equal number of practitioners indicating decreased or increased cases this quarter. AHL reported decreased cases as well as fewer strains being identified that were equally divided between field strains (6) and vaccine strains (6) based on virology data. A previously unidentified strain was BC_586-03-42857.

In January 2022, AHL introduced a combined IBDV and CAV (Chicken Anemia Virus) PCR. In Q2 there were 42 of these PCRs run resulting in 21 IBDV positive, 4 CAV positive, and 7 IBDV/CAV positive.

Inclusion body hepatitis (IBH) cases were reported to be increased compared with last quarter by most respondents. AHL reported decreased histopathology cases but stable virology PCR testing. Genotyping on confirmed cases identified both FAdV08b and FAdV11 in birds <14 days and >14 days old. FAdV08b continues to be more common.

The number of flocks with infectious bronchitis virus (IBV) were reported as stable by the majority of poultry practitioners and decreased by AHL. Again, two strains of DMV (IBV_DMV_ON_21-017385 and IBV_DMV_ON_15-077145) were identified by AHL. The most common isolate was IBV_DMV_ON_21-017385. The remaining isolates were vaccine related (AHL_Conn or AHL_Mass).

Submissions to the AHL of confirmed runting and stunting syndrome (RSS) caused by astrovirus were increased this quarter but the suspect cases were decreased. AHL reported 14 compatible and 2 suspect lesions in broilers at <14 days of age and 4 compatible and 4 suspect lesions in broilers >14 days of age. The majority of the practitioners reported RSS as being stable.

Histomoniasis was reported stable to slightly decreased by practitioners.

Ascites was reported by practitioners as stable to slightly increased but this condition is not usually identified in the spring.

Coccidiosis and necrotic enteritis cases were reported as stable by the practitioners. The AHL also reported stable coccidiosis cases, identifying the lesions in the small intestine.

Spiking mortality was reported as stable this quarter by practitioners.

Condemnation issues were reported as stable to slightly increased by veterinarians this quarter and included cellulitis, ascites, airsacculitis, and hepatitis. AHL reported liver hemorrhage, heart failure and IBV in DOAs.

Proventricular and ventricular lesions were reported as decreased by AHL. There was 1 case of necrotizing ventriculitis that appeared to be bacterial on histopathology.

Other diagnostic findings reported by practitioners included very early cannibalism (5 days of age) in an organic flock (unknown cause), and significant mortalities due to heat. AHL identified the following cases: sinusitis (E. coli, P. aeruginosa), conjunctivitis, and granulomatous hepatic necrosis.

Slaughter provincial plants: Processing volume ranged between 1.56M to 1.72M. The top 2 condemnation conditions were reported as dead on arrival (DOA) and cellulitis.

Slaughter federal plants: Processing volume ranged between 15.6M to 21.4M. Cellulitis, hepatitis and ascites were reported as the main conditions for condemnation.

Broiler-Breeders

Early systemic bacterial infections (<14 days) were reported as stable by practitioners. Bacteria isolated included E. coli. AHL reported slightly increased numbers compared to the previous quarter. E. coli continues to be the most common isolate either alone or in combination with E. cecorum. In 1 case of yolk sacculitis, E. coli and C. perfringens were both isolated.

Other causes of early mortality reported by practitioners and AHL were stable to slightly increased this quarter. Practitioners mentioned dehydration while AHL diagnosed dehydration/urate nephrosis and visceral gout.

Pre-lay mortality (> 14 days, < 20 weeks) diagnosed by AHL were due to intussusception, mycotic pneumonia (A. fumigatus), bacterial salpingitis, and bacterial septicemia (due to either S. aureus or E.coli, combined with E. cecorum or P. aeruginosa; E. coli alone; E. coli, E. cecorum, and C. perfringens). A case of vertebral osteomyelitis identified a mixed infection with E. coli, E. cecorum and C. perfringens.

In-lay bacterial septicemia was reported as stable by practitioners and slightly increased by AHL. Practitioners listed E.coli, and G. anatis as commonly isolated bacteria. AHL identified either pure culture of S. aureus or E. coli, or both. However, mixed cultures were more commonly identified including: E.coli and E. cecorum with either S. aureus, C. perfringens, G. anatis, or G. anatis and S. aureus. Practitioners report cases of multi-drug resistant E. coli as stable.

One practitioner commented that in cases of mixed bacterial infections, the combined drug resistance patterns leave few options for treatment. Recurring infections often have different resistant patterns from the first infection.

Other causes of in-lay mortality identified by the AHL included salpingitis, cannibalism, liver hemorrhage, amyloidosis, and renal interstitial fibrosis (unknown cause).

Bacterial, viral, developmental and nutritional lameness were reported as generally stable by practitioners but AHL reported a slight increase in bacterial lameness for this quarter. S. aureus and E. coli were the most common bacterial cause of lameness reported by practitioners and AHL. At AHL there were also mixed infections of S. aureus with either E. coli or P. aeruginosa.

Cellulitis/ dermatitis, particularly over the head and neck, was diagnosed in 2 cases at AHL this quarter. Mixed bacterial infections were identified in each case (E. coli/S. aureus, E.coli/E. cecorum/Avibacterium sp.).

IBV infections were reported as stable by practitioners to slightly decreased by AHL. The main strains detected were: CU82792, DMV, California, IBV_ON_AHL19-032390, and a vaccine strain (MA5). Two DMV strains were detected with IBV_DMV_ON_21-017385 still being the most common.

Fowl cholera was reported by practitioners as stable and associated with lameness related to vaccination.

The number of coccidiosis and necrotic enteritis cases reported by practitioners were stable this quarter. AHL reported an increase in coccidiosis cases with cecal coccidiosis being the most common.

Histomoniasis and Fowl pox remained stable as reported by practitioners. One case of Histomoniasis was identified at AHL.

Aggression, cannibalism, disease related hatchability issues, and mycoplasmosis were reported as stable for this quarter. One case of Mycoplasma synoviae was mentioned.

Poultry practitioners reported a variety of Salmonella isolates including: S. Livingstone, S. Hadar, S. Mbandaka and S. Putten. One practitioner mentioned that they only saw Salmonella isolated from environmental samples.

Other diagnoses reported by AHL included bacterial pneumonia (E. coli alone or with E. cecorum and S. aureus), airsacculitis, sinusitis (E. coli, E. cecorum, S. aureus, G. anatis), hydropericardium, and eye lesions. There were 2 cases with severe inflammatory eye lesions but the initiating cause was not identified.

Layers

Overall, good and stable health status for this quarter.

Early systemic bacterial infections (<14 days) were stable to slightly decreased for this quarter. AHL isolated E. coli from cases of septicemia.

Practitioners identified dehydration as another cause of early mortality. Other causes of early mortality identified at AHL included urate nephrosis/visceral urates, dehydration, and oral necrosis/osteomyelitis.

In-lay mortality (>20 weeks) was stable at AHL. Cases of septicemia identified E. coli either alone or in combination with E. cecorum. Other causes of mortality included: urate nephrosis/gout, and yolk peritonitis.

Bacterial peritonitis/salpingitis due to E. coli, E. cecorum, and G. anatis were stable as reported by practitioners. Also, multi-drug resistant E.coli was reported as stable.

Focal duodenal necrosis (FDN) was reported as stable to slightly increased by practitioners. This condition is starting to be identified more frequently and it is often associated with a history of decreased egg size. No cases were diagnosed at AHL.

IBV with drop in production and abnormal eggs was reported as stable to slightly decreased by practitioners and IBV with respiratory issues was reported as stable by practitioners. At AHL, IBV cases were slightly increased since last quarter and the following strains were identified: DMV, IBV_ON_AHL22-001651, and multiple vaccine strains (Mass MA5, Conn, GA2012).

Mycoplasmosis was identified as stable by practitioners and there is 1 mention of a diagnosis of M. synoviae.

Necrotic enteritis and coccidiosis cases were reported as stable by practitioners. One practitioner identified a case of necrotic enteritis associated with coccidiosis in a flock of young layers that responded well to treatment.

Aggression and hysteria were reported by practitioners as stable for this quarter.

The most common Salmonella isolate was S. Enteritidis. SE has a serious impact on the layer industry due to the zoonotic potential of this organism.

Other diagnoses by practitioners included fatty liver hemorrhage, and vaccination reaction (neck). AHL identified a variety of other diagnoses including fatty liver hemorrhage, lymphoid neoplasia, renal interstitial fibrosis, comb necrosis (E. coli, E. cecorum, G. anatis, C. perfringens, Bacteroides vulgatus), cutaneous necrosis (head), eyelid follicular cysts, and ventricular mucosal necrosis.

Turkeys

Early systemic bacterial infection (<14d) was reported as stable to decreased by practitioners. At AHL, septicemia was diagnosed on histopathology.

Other causes of early mortality (<14d) were stable to slightly increased with starveout being listed as a cause. At AHL there was a case of necrotizing bacterial ventriculitis diagnosed.

Late systemic bacterial infections (>14d) were stable to slightly increased. One practitioner reported a case of E. coli airsacculitis. At AHL there was also a slight increase in cases since last quarter with E. coli isolated alone or in combination with E. cecorum or P. aeruginosa.

Practitioners reported cases of multi-drug resistant E. coli as stable.

Practitioners reported stable causes of respiratory disease. AHL reported 1 case of sinusitis/airsacculitis.

A case of Mycoplasma synoviae was reported by 1 practitioner.

Necrotic enteritis, enteritis and coccidiosis were reported as stable by practitioners. AHL identified 2 cases of coccidiosis in the small intestines and 2 case of necrotic enteritis.

Veterinarians and AHL reported tenosynovitis due to reovirus as stable this quarter. AHL had 1 case positive for reovirus on PCR and 1 case that was suspicious for reovirus on histopathology.

Two cases of tibial dyschondroplasia were reported by the AHL.

Aggression and cannibalism were reported as stable to slightly increased by practitioners.

Histomoniasis (blackhead) was reported as stable this quarter and no cases were diagnosed at AHL.

Other conditions reported as stable this quarter by practitioners included ORT, and Salmonellosis (clinical). Round heart was reported as stable to slightly decreased.

Other diagnoses identified by AHL included tenosynovitis, arthritis/osteomyelitis, intersitial hepatic fibrosis, round heart, dehydration, and histologic lesions suspicious for Turkey Viral Hepatitis.

Provincial slaughter plants: Processing volume ranged between 1,400 to 50,000. The top 3 conditions of condemnation were cellulitis, abscesses and air sacculitis.

Federal slaughter plants: Processing volume ranged between 500,000 to 900,000. The top 2 conditions of condemnation were dead on arrival (DOA) and cellulitis.

Rural/Backyard/Non-Quota Flocks

AHL continues to receive numerous submissions from backyard flocks. The majority of cases include various breeds of chickens.

The AHL reported an increased number and variety of intestinal parasites. Nematodes (Ascaridia and Heterakis) were identified most frequently followed by coccidiosis (small intestine and ceca) and tapeworms.

Marek’s disease continues to be diagnosed and the number of cases increased this quarter. Other neoplasia cases also increased including squamous cell carcinoma, carcinoma and adenocarcinoma.

Practitioners continue to identify more cases of Streptococcus suis infections that tend to occur in a wide range of flocks. The AHL identified multiple cases of bacterial septicemia involving mixed bacterial infections (Salmonella Uganda, E. coli, P. aeruginosa, C. perfringens, E. cecorum; E. coli, E. cecorum, C. perfringens).

The AHL identified 2 cases of mycotic pneumonia, tracheitis and airsacculitis.

One case of ILT was diagnosed by AHL in small/exhibition flocks. Unfortunately, the isolate was too weak to type.

The most encountered clinical cases reported by practitioners were bumblefoot, Mycoplasma synoviae, Mycoplasma gallisepticum, Marek’s disease, tumours, blindness, feather pecking, lice, mites, and intestinal parasites (coccidia, roundworms, tapeworms).

AHL reported a large variety of diagnoses: salpingitis, urate nephrosis/visceral gout, cannibalism, emaciation, right heart failure, atherosclerosis, entrapment, lymphoplasmacytic dermatitis (head), umbilical hernia/ulceration, grass impaction, vent trauma, epidermal/dermal ulceration, and toxicity (Celandine or St. John’s wort).

Other species examined at AHL included one duck that was suspicious for Leukocytozoon.

Poultry research from Ontario and beyond

Characteristics of Broiler Chicken Breast Myopathies (Spaghetti Meat, Woody Breast, White Striping) in Ontario, Canada – https://www.sciencedirect.com/science/article/pii/S0032579122000529?via%3Dihub

Strategies for enhancing immunity against avian influenza virus in chickens: a review – https://pubmed.ncbi.nlm.nih.gov/35297706/

Respiratory health of broilers following chronic exposure to airborne endotoxin – https://pubmed.ncbi.nlm.nih.gov/35483171/

Big data-based risk assessment of poultry farms during the 2020/2021 highly pathogenic avian influenza epidemic in Korea – https://pubmed.ncbi.nlm.nih.gov/35671297/

Risky business in Georgia’s wild birds: contact rates between wild birds and backyard chickens is influenced by supplemental feed – https://pubmed.ncbi.nlm.nih.gov/35508913/

Events and News

Poultry Industry Council events: https://www.poultryindustrycouncil.ca/events

Poultry Health Research Network information, events, and lectures can be accessed on the PHRN website: https://phrn.net/ or on the PHRN YouTube channel: https://www.youtube.com/user/PoultryHRN

Thank You!

We thank the following poultry veterinarians who completed the veterinary survey: Dr. Elizabeth Black, Dr. Joanne Dias, Dr. Shahbaz Haq, Dr. Anastasia Novy, Dr. Mike Petrik, Dr. Erin Preiss, Dr. Joanne Rafuse, Dr. Steph Rheaburgen, Dr. Fernando Salgado-Bierman, Dr. Kathleen Sary, Dr. Ben Schlegel, Dr. Chanelle Taylor, Dr. Brenna Tuer, Dr. Lloyd Weber, Dr. Alex Weisz, and Dr. Jessalyn Walkey.