Page 6 - National Poultry Newspaper

The effects of severe heat stress in meat chickens
n Using electrolyte supplementation to minimise impacts
UNIVERSITY of Sydney principal investigator Jeff Downing provides a final report summary on the electrolyte supplementa- tion of meat chickens to alleviate the adverse ef- fects of severe heat stress.
Meat chickens may be Good shed insulation and
tion of carbon dioxide in their blood, which increas- es blood pH.
For both experiments, the birds were exposed to a temperature pattern that could be expected in a commercial shed during hot weather.
males of the same age. Giving electrolyte sup- plements one day before expected high tempera- tures (and heat stress) did not significantly affect mortality or improve per- formance and meat quality. The combined results of this study and the previous study suggest that electro- lytesaremosteffectiveun- der conditions of moderate heat stress when given for at least 2-3 days before the
Several strategies are needed to minimise the impact of heat stress on bird welfare and produc- tivity
The objectives of the re- search project were aimed to determine whether sup- plementing meat chick- ens with electrolytes in the final few days of the production period during high temperatures would improve carcass quality and performance and re- duce the effects of dehy- dration and physiological stress during transport and lairage.
Meat chickens can suffer from heat stress during pe- riods of high temperatures or humidity, which can re- duce their feed intake and increase mortality.
However, when outdoor summer temperatures ex- ceed 28-32C, it is difficult to keep the indoor tem- perature within the ideal thermal comfort zone of 18-22C.
However, this can reduce their ability to retain water and can cause dehydration, which may worsen poten- tial stressors associated with pick-up and transport. The efficacy of electro- lytes to minimise heat stress was assessed
Standard husbandry and nutrition were provided un- til the birds were 39 days old.
Heat stress continues to be a concern for the wel- fare and productivity of meat chickens in regions of high summer ambient temperatures.
raised in regions with high temperatures
evaporative cooling can re- duce shed temperatures by 8-10C.
To mitigate these effects, meat chickens will excrete higher amounts of salts in their urine.
Heat-stressed meat chick- ens are also less productive andproducelowerquality meat.
Meat chickens can be particularly susceptible to heat stress in the days be- fore pick-up for transport to the processing plant, when their weight is at its highest.
At this point, the tem- perature was gradually increased to 32C during the day, and then reduced to 20-22C, to replicate the normal summer tempera- ture cycle.
When determining the potential for birds to expe- rience heat stress, ambient temperature and humidity should be considered to- gether.
Meat chickens can produce a considerable amount of heat themselves but will experience heat stress due to a variety of other factors, particularly body weight, and the air temperature and relative humidity in the shed.
To manage heat stress, meat chickens rely on pant- ing to dissipate heat, but this raises the concentra-
A common strategy for minimising heat stress in meat chickens is supple- mentation of their water supply with salts, called ‘electrolytes’, for a short time before pick-up.
Birds were given one of two electrolyte formula- tions, for either one or three days before processing.
expected hot weather.
A key finding of this study was the difference in temperature between the air at the level of the birds’ backs and the temperature under birds sitting on the
Electrolytes given imme- diately before hot weather appear to have some bene- fit in mitigating heat stress.
Meat chickens can suffer from heat stress during periods of high temperatures or humidity, which can reduce their feed intake and increase mortality.
The aim of this research project was to determine whether electrolytes could minimise heat stress at air temperatures above 28C, at one day and at three days before pick-up and processing.
This could be related to differences in body weight, because males are usually heavier than fe-
This finding has implica- tions for older birds that are larger and much more likely to spend time sitting.
For the final report see agrifutures.com. au/product/electrolyte- supplementation-to- alleviate-the-adverse- effects-of-severe-heat- stress-in-meat-chickens
Previous research funded by AgriFutures Australia found that electrolyte sup- plementation two days be- fore transport, and at air temperatures of 26-28C, improved animal outcomes and meat quality.
After the carcasses were collected at the process- ing plant, random samples were assessed for meat quality.
floor.
While it was not possible
However, several strate- gies are needed to mini- mise the potential for heat stress and to limit produc- tion losses, welfare issues and mortality.
However, supplementa- tion for five days before transport improved growth performance but had lim- ited effects on meat quality.
When chickens were exposed to temperatures above 28C before pick-up, unsurprisingly, there were increases in the mortality rate and number of birds needing to be humanely euthanised.
In one instance, the max- imum temperature differ- ence was 10.9C.
Farmers should have sound understanding of the temperature and humidity predictions for their region, and use strategies to reduce the risk of heat stress when high predicted outside tem- peratures (> 32C) make it difficult to keep shed tem- peratures below 26-28C.
In those experiments, chickens started to show signs of severe heat stress at 28C.
While there were no dif- ferences in weight loss dur- ing transport or meat qual- ity, between treatments, fe- males responded less than males to the treatments.
This suggests that heat stress could be more severe than previously thought be- cause the heat under seated birds could have a great- er effect than the ambi- ent temperature in a shed alone.
Electrolytes are most effective when supplied for three days before hot weather
to determine how long the birds had been sitting be- fore the temperatures were taken, the average tem- perature under the seated birds was 4.4C higher than the temperature at the level of the birds’ backs when standing.
The most effective way to improve performance in hot weather is through good housing design.
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Page 6 – National Poultry Newspaper, November 2021
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