Pig_Summer14_p16-17:FB_0606_p12-13_Marketing.qxd 06/06/2014 13:01 Page 16 POULTRY HEALTH Hot and bothered Devon-based poultry vet Ben Crisp (BVSc MRCVS) says that while warm and dry weather is, theoretically, good for both humans and poultry, excessively warm days can take their toll on broilers and laying birds Chickens are designed to be able to produce and lose heat easily and with little effort between set ambient temperatures. Once the ambient temperature and, therefore, the temperature of the bird rises above the ‘upper critical limit’ then the bird has to actively lose heat via open mouth breathing. Eventually, however, excessive open mouth breathing leads to more heat being produced than the heat that is lost. At this critical turning point the bird is under ‘acute heat stress’ and should this continue the bird then becomes ‘chronically heat stressed’. While temperatures above 27°C or relative humidity above 50% are enough to cause panting, the negative effects of heat stress can be seen at temperatures above 24°C. However it must be remembered that this will vary depending on the age of birds and the relative humidity. release of heat shock proteins. Their function is to shut down metabolic reactions to protect vital organs. Post-mortem findings usually include congested carcases, varying in severity, depending upon how long birds have been heat stressed for. Generally the carcases are dry and tacky to the touch. Blood is darker and thicker than usual. There may be a mucoid exudate found in nostrils or mouth, again depending upon the severity of heat stress. The effects of elevated temperatures on poultry “Encourage birds to drink and provide electrolytes in the drinking water” When temperatures rise above 43°C birds are at risk of hyperthermia and death if immediate action is not taken. It is worth noting that a sudden increase in environmental temperature, typically above 5°C, can induce acute signs of heat stress even with relatively low overall temperatures. The broiler can adapt to higher temperatures, but it takes about five days for this to occur. HEAT-STRESS SIGNS Visible signs of heat stress include panting, a gradual or spike in water consumption and a reduced 16 feed intake as the birds try to limit their movements around the shed. In a layer environment, egg production can acutely reduce. Birds will often stretch out their wings and legs in an attempt to increase their surface area and aid heat reduction. There are also a number of invisible signs that can have a neg- ative effect on the bird. The pH of blood plasma rises while the pH of cells falls. The urine output of the bird will increase and, with this, so does the quantity of electrolytes. The birds’ resources are being diverted to heat loss and so production, whether it be weight or eggs, will be negatively affected. There is also thought to be the SO, WHAT ARE THE POTENTIAL HARMFUL EFFECTS OF HEAT STRESS IN BIRDS? ● A decrease in egg size when temperatures exceed 24°C and, in extreme cases, the cessation of egg laying altogether ● Dehydration, which if severe enough can kill birds ● Prolonged heat can induce a moult in birds ● A decrease in the function of the immune system ● Prolonged and excessive sunlight can lead to a reduction in the colour of egg shells ● Temperatures above 43°C can lead to death by hyperthermia ● Reduced feed intake leading to poor production. WHAT CAN BE DONE TO IMPROVE THE SITUATION? All strategies are designed to lower the ambient temperature or Pig&PoultryMarketing Summer 2014 Pig_Summer14_p16-17:FB_0606_p12-13_Marketing.qxd 06/06/2014 13:01 Page 17 POULTRY HEALTH increase the ability of the bird to lose heat. This, in practice, involves increasing the ventilation and openings to allow fresh air to flow in and pull out warm air. This will also help to increase the air speed across each bird. Higher air speeds ensure adequate removal of the hot air boundary surrounding each bird, aiding convectional heat loss. This is particularly important when birds are close to peak stocking densities. “While temperatures above 27°C or relative humidity above 50% are enough to cause panting, the negative effects of heat stress can be seen at temperatures above 24°C” Increased flow also removes humid air, a by-product of breathing. Reducing humidity allows panting to be more efficient. Recommended air speed in hot weather is between 1.5 and 3 metres per second. This will need to be measured at bird level and, in practice, to achieve 3m per second will be difficult in all but the more modern sheds. Looking at long-term investment, there are now renewable systems that can be used in both cooling and heating modes and will both cool the air and the ‘under-floor’ heating pipes, allowing complete environmental con- trol whatever the weather. Try to provide shade for your birds if they are a free-ranging flock, although with certain farms established trees will already be doing this job. Encourage birds to drink and provide electrolytes in the drinking water. The electrolytes are designed to rebalance the potassium and carbonate level to reduce the alkalosis. Electrolytes are more efficient at hydration than plain water alone and will help to reduce mortality due to dehydration. If birds are panting and stressed then avoid stimulating the birds. This may even involve avoiding a shed walk in the heat of the day or, in some situations, changing the feeding patterns. But this can cause problems due to rushing for the food when reintroduced, so it should only be carried out under consultation with a vet and feed adviser. Reducing stocking density can also greatly reduce the heat produced in a house. This is particularly true for broiler farms. However, catching and transporting birds on a severely hot day can cause even more problems with heat stress and higher mortality levels in those birds being moved. Platinum Pla tinum P Programme rog gramme 1 - BioT BioTurbo Turbo urbo Ultra-Powerful Foam Foaming ming Cleaner 8 8 * ' :* ) k $ 8Customer # ' + ; 8Comment ' + + ; ) # 2 - Bi-OO-Cyst Super Strength Phe Phenol enol Disinfectant Bacteria/Viral/Yeasts/Moulds/Cocci Bacteria/V Viral/Yeasts/Moulds/Cocci Truly Truly Broa Broad ad Spectrum 3 - BioShield P Spray/Fog - Formald Formaldehyde dehyde Free Three Hour Hou ur Re-Entry T Time ime Better Price Pric ce An industry leading g programme. 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