Skeletal Disorders in Poultry

Prof.R.N.Sreenivas Gowda

Introduction

Skeletal problems in poultry are a significant concern, leading to lameness, reduced growth, and increased mortality. These problems can stem from various factors, including genetics, nutrition, and infectious diseases. Common issues include tibial dyschondroplasia, rickets, and various leg deformities. Losses due to skeletal problems in poultry are caused by an increase in  reduced FCR, increased mortality and the number of cull birds, increased condemnations from septicemia-toxemia, and more downgrading from the trimming of breasts and legs.

Causes and Contributing Factors:

• Genetics: Rapid growth rates in broiler breeds can increase bone disorders.
• predispose them to skeletal problems.
• Nutrition: Deficiencies in vitamin D, calcium, phosphorus, or other essential nutrients can impair bone development.
• Rearing Conditions: Inadequate litter management, slippery surfaces, and overcrowding can exacerbate leg problems.
• Infectious Diseases: Viral and bacterial infections can affect bone development and joint health.
• Environmental Factors: Poor ventilation and temperature control can contribute to skeletal issues.

 Noninfectious Skeletal Disorders 

• Tibial Dyschondroplasia(TD): A disorder where cartilage fails to fully replace by bone, resulting in a permanent plug of cartilage in the long bones of rapidly growing birds. TD characterized by an abnormal accumulation of cartilage in the growth plate of the long bones, often leading to lameness.

• Fig: 1.Tibial dyschondroplacia- Widening of abnormal cartilage masses under the growth plates of long bones. (Source: google Images)
• Rickets: This condition is caused by a deficiency in Vitamin D, calcium, or phosphorus, leading to poor bone mineralization and soft, deformed bones in growing birds resulting in soft, deformed bones.

Fig: 2. a) increased width of the growing plates b)Beaded costrochonral joints, c)       Curved and deformed keel bone (sternum).         

• Leg Deformities: Various forms like valgus (bow-legged) and varus (knock-kneed) deformities, twisted legs, and slipped tendons can occur.

Osteoporosis:

• Bone density loss, making bones brittle and prone to fractures, particularly in laying hens:
• Cage layer fatigue is a form of osteoporosis seen in laying hens

Fig:4. Difference between normal healthy bone matrix and an osteoporetic bone. (Source: This image is from www.drwolgin.com)

Articular Gout: A condition where uric acid crystals accumulate in joints, causing inflammation and pain.

Fig: 10. Articular Gout; Deposition of ureatic crystals joints  (Source:Diseases of Poultry-van Dinev2010)

Degenerative Joint Disease: Includes conditions like femoral head necrosis

Femoral Head Necrosis: Degeneration of the femoral head, causing lameness and affecting mobility.

Fig.5 Femoral head necrosis: Normal head of femur, asterisk (★) shows the fovea for ligament of femoral head; FHS – femoral head separation (epiphyseolysis); FHT – femoral head transitional degeneration; FHN – femoral head necrosis; Arrow head (▶) indicates bacterial fibrosis. (Google image)

• Spondylolisthesis:

Abnormal curvature or slippage of vertebrae, sometimes leading to spinal cord compression.

Fig:6. (1) Clinical sign of vertebral osteomyelitis. (2) Gross changes in the vertebral osteomyelitis showing enlargement of affected vertebral body. (source: google image)

Infectious Skeletal Disorders

• Bacterial Osteomyelitis and Arthritis:

• Inflammation and infection of the bone and joints, often resulting from bacteria entering the bloodstream or from infected tissues.

• Viral Arthritis:

• Inflammation of tendons and joints caused by certain strains of reoviruses.

• Osteopetrosis:

• Caused by infection with certain avian leukosis/sarcoma viruses, which alter bone development and growth.

Marek’s Disease: A viral disease that can cause nerve damage and paralysis, affecting mobility.

Fig:9.   Marek’s disease: paralysis of legs –sportsman posture

• Bacterial Chondronecrosis:

Bacterial infection leading to cartilage damage and bone lesions. Vertebral BCO: also is known as vertebral osteomyelitis, spondylitis, spondylopathy, and more recently albeit incorrectly as “kinky back.

Fig:8.  Bacterial Chondronecosis of vertebral column

Impact of Skeletal Problems:

• Lameness and Reduced Locomotion:

• Difficulty in walking, reaching food and water, and reduced overall activity.

• Poor Growth and Reduced Feed Efficiency:

• Lameness can hinder growth and increase the time it takes for birds to reach market weight.

• Increased Mortality:

• Birds may be unable to access food and water, leading to starvation or dehydration.

• Carcass Condemnation and Downgrading:

• Skeletal abnormalities can lead to carcass downgrades or condemnations at processing.

• Economic Losses:

• Reduced production, increased mortality, and condemnations result in significant financial losses for producers.

• Welfare Concerns:

• Skeletal problems can cause pain and distress, impacting overall bird welfare.

Management and Prevention:

• Optimizing Nutrition: Ensuring a balanced diet with adequate levels of essential nutrients.
• Selecting Appropriate Genetics: Choosing strains with better leg conformation and growth characteristics.
• Managing Rearing Conditions: Providing adequate space, proper litter management, and appropriate temperature and humidity.
• Controlling Infectious Diseases: Implementing biosecurity measures and vaccination programs.
• Regular Monitoring and Assessment: Conducting lameness scoring and skeletal assessments to identify and address issues early.

In conclusion skeletal problems in poultry include noninfectious conditions like rickets, dyschondroplasia, leg deformities (valgus/varus), and osteoporosis (such as cage layer fatigue), often caused by nutritional deficiencies or rapid growth. Infectious causes, such as bacterial osteomyelitis, viral arthritis, and osteopetrosis, are also significant, leading to lameness, poor growth, and carcass condemnation

(Acknowledgements: Google images)