There are different types of stresses, namely:
Climatic stress (heat stress and cold stress)
Managemental stress (excess light, wet litter and poor ventilation)
Nutritional stress (excess salt and low nutrients)
Physiological stress(rapid growth, sexual maturity)
Physical stress (catching, injection, immobilization and transportation)
Social stress (overcrowding, poor body weight)
Psychological stress (fear and harsh caretakers)
Among all these types of stressors, environmental stress adversely affects the production performance of commercial poultry. In general the ideal temperature for optimum poultry production is 65-75oF. Birds like mammals are homoeothermic which means they can maintain a relatively constant deep body temperature 41.7oC (107oF).
The environment in which poultry is maintained is the single most important factor affecting productivity. The thermoregulatory mechanism in birds is effective only upon the ambient temperature within certain limits (18-28oC). Beyond this bird cannot adjust well. The upper lethal temperature in birds is about 47o C (116.8oF), this is called thermo neutral or zone of comfort during which birds do not change their behavior or signs of discomfort and use minimum amount of metabolic energy to maintain homoeothermic range of body temperature. Within the thermo neutral zone, body temperature is maintained by the thermal equation (heat production=heat loss).
1.0 Management in Poultry Farming in Summer.
Summer season causes number of deleterious effects on broilers and layers which ultimately reduces profitability. Summer stress a serious concern for poultry producers as it directly leads to financial losses by impaired poultry performance.
What happens in heat stress?
Birds become heat stressed when they have difficulty in achieving balance between body heat loss and body heat production, the normal body temperature of poultry being 41°C. When environmental temperature exceeds 35o C bird is likely to experience heat stress. In an effect to maintain body temperature birds first rely on losing heat from blood vessels near surface of skin by process called non-evaporative cooling. However, this mechanism is only effective when ambient temperature is lower than bird’s body temperature. As ambient temperature increases beyond bird’s thermo neutral zone, non-evaporative cooling becomes ineffective. At these higher temperatures, bird relies on panting / evaporative cooling as mechanism for controlling body temperature. Panting is an effective but energy expensive way for the bird to control body temperature and typically results in lower feed intake and growth as well as reduced feed efficiency between 20-30o C feed intakes is reduced by 1-1.5% for 1o C rise in temperature and by 5% above 32o C.
The will increase water intake to offset water loss but situation is complicated by the fact that body’s ability to retain water is reduced as the evaporative cooling process escalates. During high ambient temperatures, the birds increase panting up to 10 times from a normal rate of 25 breathes/min to 250 breathes/min .This leads to an excessive loss of carbon dioxide resulting in raised blood plasma bicarbonate levels and increased blood ph. The bird attempts to correct blood ph by excreting bicarbonates via urine. Bicarbonates are negatively charged ions that must be coupled with positively charged ions such as potassium to be excreted in urine. However, as potassium is important in maintain intracellular water balance, a loss of potassium ions via urine reduces ability to maintain this water balance. Consequently, while birds do compensate for water losses associated with panting by consuming more water, its retention in the body cells is limited by simultaneous loss of electrolytes such as potassium in urine.
1.1 Effect of Heat in Poultry Farming in Summer.
Most important effect of heat stress is decrease in body resistance and more susceptibility to E.coliand CRD etc. In summer outbreaks of gout may be seen in broilers and layers. In heat stressed birds blood flow increases to upper respiratory tract, skin and abdominal muscles for relieving heat, however, blood flow to intestinal tract is decreased. As a result there is reduction in appetite leading to lower feed intake. Concurrently water intake is increased resulting in fluid contents in intestinal tract. This further cause’s diarrhea that results in loss of electrolytes needed to maintain acid base balance.
1.2 Clinical Sign and Symptom.
The following clinical signs will be observed in heat stressed birds:
More intake of water
Reduction of egg production
Poor egg shell quality
Less body weight gain in broilers
Reduced feed efficiency
Increase in body temperature
1.3 Post Mortem Lesions.
Mucoid exudates in mouth and nostrils
Pale breast muscles
Congestion of liver, spleen, kidney and lungs.
Fluid contents in intestines.
Rapid decomposition of carcass
2.0 Steps to Combat Heat Stress in Poultry Farming in Summer
The aim of adopting measures to combat heat stress is not only to keep birds alive but also to get production out of them to achieve targeted figures i.e. number of egg from layers and a better body weight at particular age with specific FCR in broilers.
Following steps will help to combat heat stress in Poultry Farming in Summer :
2.1 Housing Management in Poultry Farming in Summer
Orient the long axis of poultry house in an east-west direction to minimize solar heating and direct access to sunlight.
Poultry houses in tropics should have good roof insulation (if possible with false roof to reduce the conduction of heat) with support of foggers and cooler systems.
In open sided houses, width of house will be a limiting factor so keep the optimum width (24-32 ft) based on temperature, humidity and wind velocity, type of house and nature of bird for effective cross ventilation.
Increased air movement over the birds by cooler fans/exhaust to produce a wind chill effect which will cool birds even without drop in the house temperature.
Shed design and construction should not allow direct sunlight on birds.
Thatching of roof with paddy straw or sugar cane leaves will reduce temperature inside the shed.
The roof should be painted with white wash to reflect light.
Shades from tall trees and plantation around the sheds can reduce the radiant heat. The plantation of trees should be such that trees will be leafy during summer and bald during winter.
Roof overhangs should be sufficient (3-5 ft) to protect the birds from strong sunrays.
2.2 Water Management in Poultry Farming in Summer
Practically water is the most important criteria of these four managemental factors during summer. In summer water consumption is 3-4 times more. Even a slight shortfall of water can lead to heat stroke and mortality. Normally feed and water consumption ratio is 1:2 but when temperature shoots beyond 95oF, this ratio may increase up to 1:4 or more.
Points to be taken into consideration:
Supply of plenty of clean and cool water (60-70oF) must be ensured during summer months.
Use Aquacure in water to control infections through water.
For day old chicks provide cool water and electrolytes on their arrival to farm before offering feed to avoid dehydration after transportation.
Cover water tanks with wet gunny bags to avoid direct exposure to sun.
Increase number of waterers by 25%.
Increase frequency of watering.
In case of nipple drinkers, insulate nipple pipe with wet gunny cloth.
Provide Electral Energy (1-2 gm/liter) in water during hot hours.
Addition of 0.25% of salt to drinking water increases water consumption.
Adjust the amounts of medications and volumes of water used for water vaccination to reflect the increase water consumption of the flock during hot weather.
Do not withhold drinking water from the flock when vaccine is provided through drinking water.
Use Aquacure in water to control infections through water.
For day old chicks provide cool water and Electral Energy on their arrival to farm before offering feed to avoid dehydration after transportation.
Cover water tanks with wet gunny bags to avoid direct exposure to sun heat.
Increase frequency of watering.
2.3 Feed Management in Poultry Farming in Summer.
During summer consumption of feed by birds is reduced considerably leading to reduced body weight, egg production and shell quality.
Increase the frequency of feeding.
Do not offer feed during day time in broilers.
Certain changes in feed formulations are necessary.
Increase nutrient density of feed to compensate for depressed feed intake.
Energy of feed should be reduced. Crude protein content should not be increased because heat generated by one gram of fat is 16.5% or one gram of fat is 22.5%.
Similarly 20-30% extra vitamins and trace minerals should be added to feed.
Available phosphorus content of feed should be increased.
Vitamin C is necessary to maintain integrity of blood vessels. Supplementation of vitamin C @ 200-500 gm /ton feed will be beneficial.
Grow E-Sel @ 50 gm /ton feed will also be beneficial.
Pelleted feeding is beneficial where low energy fiber diets are used
Add soda-bicarbonate @ 0.1% for improvement of shell quality.
Since hot humid climate favors growth of moulds/fungi in feed, so constant use of anti-fungal is recommended.
The diet should be balanced with limiting amino-acids, methionine and lysine which will give better results.
Increase the calcium level from 3-3.5% in layer diet.
Inclusion of Growvit-A and Grow E-Sel 250mg /kg diet for better performance and combat heat stress.
2.4 General Management in Poultry Farming in Summer.
Litter preferably fresh litter of 2 inches thickness with racking or stirring of litter 2-3 times a day during cool hours is recommended.
10% extra floor space should be provided in summer.
Overcrowding of birds should be avoided.
Shifting, transportation, de-beaking and vaccination should be done during night or cool hours of the day.
Birds severely heat stressed may be dipped in cold water for 2-3 minutes keeping their neck and head above water level.
Provide proper cross ventilation.
Fans (pedestal, ceiling or exhaust) may be fitted in sheds.
Use foggers in the shed which could reduce the shed temperature up to 5-10oC depending upon quality.
Use of paint ,white lime etc practically reduces the shed temperature up to 2oC
Use side curtain in shed which should be sprinkled with water.
Provide 3 exhaust fans on one side and pad cooling on other side (200ft) which completely seals the shed sides and brings down temperature below 8oC.
Use sprinklers on the top or inside shed.
Surround the house with tall trees.
Thatched roof is suitable for hot areas.
The house should be situated away from other buildings in order to facilitate free movement of air.
High altitude of roof is ordinarily 2.6 to 3.3 m from foundation to the roof line to provide maximum ventilation.
Provide 1 meter overhang to cut the direct sun and rain into the house.