Runting-Stunting Syndrome (RSS) is one of the most challenging conditions affecting broiler chickens. It leads to poor growth, uneven flock sizes, increased feed costs, and high mortality rates in severe cases. This condition is widespread in commercial poultry farms and can severely impact profits.
RSS is not a single disease but rather a syndrome caused by a combination of viral infections, nutritional deficiencies, and poor management. The birds affected by RSS show poor weight gain, delayed growth, abnormal feathering, and weak immunity, making them prone to secondary infections.
In this blog post, we will explore the causes, symptoms, prevention strategies, and best treatment options for RSS. By understanding this condition in detail, poultry farmers can take the necessary steps to protect their flocks and ensure maximum profitability.
What is Runting-Stunting Syndrome (RSS)?
Runting-Stunting Syndrome (RSS) is a growth disorder primarily affecting broiler chickens during their early stages of development (first two weeks). Chicks affected by RSS fail to grow at a normal rate, remain significantly smaller than their healthy counterparts, and suffer from digestive and metabolic issues.
Key Features of RSS:
- Affected chicks appear stunted and weak compared to their healthy flockmates.
- The condition results in poor weight gain despite adequate feeding.
- RSS birds consume more feed per unit of weight gain, leading to high feed costs.
- Increased susceptibility to secondary infections due to weakened immune function.
- Flock uniformity is lost, making broiler processing and marketing difficult.
Causes of Runting-Stunting Syndrome (RSS)
RSS is a multifactorial condition, meaning it arises due to multiple interacting causes. Below are the most common factors that contribute to RSS in broilers:
1. Viral Infections (Major Cause)
Several poultry viruses have been associated with RSS:
- Reovirus – Causes enteritis, damaging the intestinal lining and impairing nutrient absorption.
- Parvovirus – Affects the digestive tract, causing malabsorption syndrome in broilers.
- Adenovirus – Suppresses immune function and leads to liver damage, affecting overall bird health.
These viruses primarily affect the gut and liver, reducing the ability of birds to process and absorb nutrients, leading to poor weight gain and stunted growth.
2. Poor Nutrition and Feed Quality
The quality of feed plays a major role in growth rate. Poor feed can worsen the symptoms of RSS. Nutritional causes include:
- Protein deficiency – Low protein intake leads to muscle wastage and poor development.
- Vitamin & mineral deficiencies – Lack of vitamins A, D, E, and minerals like calcium and phosphorus affects bone development and immunity.
- Contaminated feed – The presence of mycotoxins (toxins from moldy feed) damages the liver and intestines.
- Unbalanced amino acids – Methionine and lysine deficiencies slow down muscle growth.
3. Poor Brooding Management
The first few days of a chick’s life are critical for growth. Poor brooding conditions can increase RSS cases. Common management mistakes include:
- Incorrect brooding temperature – Too cold or too hot conditions stress chicks, slowing growth.
- Poor ventilation – High ammonia levels damage the respiratory system.
- Overcrowding – High stocking density leads to competition for feed and water, affecting growth.
- Poor lighting schedules – Improper light exposure can affect feeding behavior and metabolism.
4. Bacterial Infections & Secondary Diseases
While RSS is primarily viral, affected birds become highly susceptible to bacterial infections such as:
- Escherichia coli (E. coli) – Causes gut infections and diarrhea.
- Salmonella – Leads to food poisoning and poor weight gain.
- Clostridium perfringens – Causes necrotic enteritis, further damaging the intestines.
5. Immune Suppression
Weakened immune function can make chicks more prone to RSS. Factors contributing to immune suppression include:
- Poor vaccination programs – Lack of proper vaccinations increases viral outbreaks.
- High stress levels – Transport, overcrowding, and poor handling can weaken immunity.
Symptoms of Runting-Stunting Syndrome (RSS)
Early Symptoms (First Week of Life):
- Chicks appear smaller than others in the flock.
- Poor feeding behavior – birds peck but don’t consume enough feed.
- Lethargy – Reduced activity and movement.
Growth-Related Symptoms:
- Severe weight loss and stunted growth.
- Uneven flock sizes – Some birds grow normally, while others stay small.
- Poor feather development – Feathers look thin, dull, or uneven.
Digestive Symptoms:
- Watery droppings (diarrhea) due to poor nutrient absorption.
- Enlarged, inflamed intestines (seen during necropsy).
Behavioral Symptoms:
- Weak pecking behavior.
- Birds huddle together due to weakness.
Prevention of Runting-Stunting Syndrome (RSS)
1. Strong Biosecurity Measures
- Restrict farm visitors to prevent viral transmission.
- Disinfect feeders, drinkers, and equipment daily.
- Use separate clothing and footwear for farm staff.
2. Proper Nutrition & Feed Quality
- Use high-protein starter feed (22-24% protein) for the first three weeks.
- Supplement with essential vitamins & probiotics to improve digestion.
- Store feed properly to prevent fungal contamination.
3. Optimal Brooding Management
- Maintain correct temperature (32-35°C or 90-95°F in the first week).
- Provide clean, dry bedding (wood shavings, rice husks).
- Reduce stress by avoiding loud noises and excessive handling.
4. Vaccination & Disease Prevention
- Vaccinate against Reovirus, Adenovirus, and Parvovirus.
- Monitor flocks for early signs of infection.
- Use probiotics to strengthen gut health.
Best Treatment for Runting-Stunting Syndrome (RSS)
There is no direct cure for RSS, but supportive treatment can help affected birds recover.
1. Nutritional Therapy
- Offer electrolytes & vitamin supplements to boost weak chicks.
- Provide high-energy feed to help stunted birds catch up.
- Use digestive enzymes & probiotics to improve gut function.
2. Antibiotics for Secondary Infections
- Use amoxicillin or enrofloxacin for bacterial infections.
- Probiotics can help reduce harmful bacteria in the gut.
3. Environmental & Management Adjustments
- Separate weak chicks and give them extra care.
- Maintain optimal temperature and humidity levels.
Economic Impact of RSS in Poultry Farming
RSS leads to major financial losses due to:
- Increased feed costs – Birds take longer to reach market weight.
- Poor meat quality – Stunted chickens yield lower-quality meat.
- Delayed processing time – Birds require extra days to grow, reducing farm efficiency.
Estimated Loss per 10,000 Birds Affected by RSS:
- 10-20% reduction in average weight → $5,000-$10,000 loss.
- Higher feed costs → $3,000-$6,000 loss.
- Increased mortality (5-10%) → $2,000-$5,000 loss.
Total losses per 10,000 birds can range from $10,000 to $20,000, depending on severity.
Conclusion
Runting-Stunting Syndrome (RSS) is a serious issue in broiler farming that requires a multi-step approach to prevent and control. By implementing proper biosecurity, high-quality nutrition, and optimal management practices, poultry farmers can reduce RSS cases and maximize profit