Managing Layers in Summer

By Learnmore Chiposo | Supra Feeds

High environmental temperatures, often coupled with high relative humidity, are common during the summer season. These conditions can lead to heat stress in layers, which profoundly affects overall flock performance. Significant losses, including high mortality and reduced egg production, are observed when temperatures exceed 33°C. Even mild heat stress, often overlooked, can subtly impact flock performance, leading to losses in egg production and shell quality.

Thermoregulation Mechanisms in Birds

Heat is lost from an animal's body through radiation, convection, and conduction, collectively known as sensible heat loss. For layers, the thermoneutral zone (TNZ) ranges between 18–28°C. Within this range, sensible heat loss suffices to maintain a bird’s normal body temperature of 40.6–41°C. However, beyond the TNZ, the efficiency of sensible heat loss deteriorates. Birds rely on evaporative cooling via panting, which expends significant energy—540 calories are required to evaporate 1g of water. Consequently, energy diversion to cooling processes results in reduced growth and egg production, causing performance losses.

Effects of Heat Stress in Layers

Heat stress results in:

• Reduced feed intake

• Reduced egg production

• Decreased egg weight

• Poor shell quality

• Low albumen height

• Increased mortality due to immunosuppression

• Higher cannibalism rates

The extent of production losses depends on:

1. Maximum temperature exposure

2. Duration of high temperatures

3. Rate of temperature change

4. Relative humidity of the air

At high temperatures, birds display rapid, shallow, open-mouth breathing (gular reflex) to enhance evaporative cooling. Prolonged exposure leads to listlessness, coma, and death. Flocks not acclimated to high temperatures are most susceptible. Young birds exposed to high heat develop thermotolerance later in life, aided by heat shock proteins.

Relationship Between Environmental Temperature and Relative Humidity

Heat stress arises from the combined effects of temperature and humidity, termed effective temperature. Higher humidity exacerbates bird discomfort and heat stress. Producers should use temperature and humidity loggers to monitor conditions accurately. During the day, higher temperatures and lower humidity favor evaporative cooling via ventilation or foggers. Conversely, during the evening, when humidity rises, additional humidity from foggers may worsen heat stress. In such cases, increased air movement alone helps reduce stress by creating a wind-chill effect.

The Effect of Heat Stress on Eggshell Quality

Heat-stressed layers often produce eggs with thinner shells due to respiratory alkalosis caused by hyperventilation. Excessive panting reduces blood carbon dioxide levels, elevating blood pH and disrupting calcium transfer to the shell gland. Additionally, reduced feed intake further limits calcium intake, exacerbating the issue. Increasing dietary calcium does not resolve this problem; phosphorus loss also contributes to weakened shells.

Restoring Acid/Base Balance

Electrolytes in drinking water during hot periods encourage water consumption and reduce mortality in acutely heat-stressed flocks.

Drinker System Management for Heat-Stressed Flocks

• Ensure adequate water supply, with flow rates exceeding 70 ml/minute per nipple drinker.

• Provide sufficient drinker space and functionality.

• Add drinkers for floor-reared flocks to accommodate increased water demand.

• Use cooler water to lower birds’ core temperatures.

• Flush water lines in the afternoon to maintain water temperatures below 25°C.

• Insulate overhead water tanks and avoid direct sunlight exposure.

• Use vitamin and electrolyte supplements to replenish lost minerals.

Management of Heat-Stressed Flocks

• Avoid disturbing birds during the hottest times (afternoon and early evening).

• Schedule routine tasks like beak trimming and vaccinations during cooler morning hours.

• Use foggers and misters for evaporative cooling; adjust timings based on house conditions.

• Employ roof sprinklers to cool the interior of poultry houses.

• Avoid running feeders during peak heat.

• Run fans continuously at night to maximize cooling.

• Ensure air movement within bird areas reaches a minimum velocity of 1.8–2.0 m/s.

• Avoid overcrowding cages to improve ventilation.

• Transport birds during early morning or nighttime, using fewer birds per crate.

Lighting Programs for Heat-Stressed Flocks

• Adjust lighting schedules to provide more morning hours for feed consumption.

• Lower light intensity during peak heat to reduce bird activity.

• Use intermittent lighting programs to promote feed intake.

Nutritional Management for Heat-Stressed Flocks

Monitor feed consumption closely and adjust diets for amino acids, calcium, sodium, and phosphorus according to production demands. Supra Layers Feed is specially formulated for hot conditions, incorporating strategies such as:

• Avoiding feeding during peak heat.

• Using highly digestible protein sources to reduce metabolic heat production.

• Increasing phosphorus content to compensate for higher urinary excretion.

• Maintaining an optimal dietary electrolyte balance.

Vaccination Considerations During Heat Stress

• Adjust water medication volumes to reflect increased consumption.

• Complete water vaccinations within one hour.

• Avoid withholding water during hot periods.

• Exercise caution with spray vaccinations to prevent adverse reactions.

Effective summer layer management requires an integrated approach involving thermoregulation, nutrition, water management, and housing modifications. Supra Feeds is committed to supporting farmers with innovative solutions to optimize flock performance during the challenging summer months.