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study, under the conditions of full ventilation and low ambi- ent temperature (10°C), when compared to the other two groups of hens, the provision of warm perches prevented an increase in feed consumption while body weight and egg production rate were maintained. Egg production and quality are closely related to circulating calcium availability. During exposure to cold, chickens experi- ence vasoconstriction which reduces the flow of an adequate blood supply to the gut and uterus – impairing nutrient ab- sorption and eggshell calcium deposition. In this study, eggs collected from hens in the warm perch system had thicker eggshells than those from both the regular perch and no perch systems by the end of the three week trial period. The researchers concluded that installing a warmed perch system for laying hens enables the birds to cope better with low am- bient temperature and utilise calcium better during eggshell formation. Other egg quality measurements did not differ between the three perch systems.


The results show that a warmed perch system could provide a novel thermal device to help reduce cold stress during the winter season without compro- mising air quali- ty in the poultry house.


The researchers noted that: “The provision of warm perches could allow the chickens to gain heat from the warmed perches which, in turn, reduces the need for endogenous heat production from the conversion of T4 to T3. Therefore, the higher T4 in the hens using the warm perch system can be considered an indicator of an ameliorated stress response further to the provision of warm perches. While the higher T4 levels found in the no perch hens probably resulted from the increased metabolic and digestive heat resulting from the ex- cessive feed intake that was observed in that group”.


Egg production and egg quality Looking at several studies, low ambient temperatures in lay- ing hens lead to an increase in feed intake, while egg produc- tion, egg quality and feed efficiency decrease. In the current


Table 1 – Effects of warm perches on body temperature, feed intake, BW loss and egg production in cold-stressed laying hens.


Measurement Rectal temperature (°C)


Foot surface temperature (°C) Feed intake (g)


Body weight loss (%) Hen-day egg production (%) 14


Perch system No perches 40.29 13.01 141.7 8.0


84.9


Regular perches 40.66 18.39 133.9 10.0 87.8


▶ POULTRY WORLD | No. 2, 2022


Warm perches 40.64 29.14 121.3 5.3


93.6


Immune regulation Prolonged exposure to environmental stressors can weaken the immune system, leading to immunosuppression. Studies in chickens have reported that cold stress decreases the num- ber of lymphocytes which leads to an increased heterophil to lymphocyte ratio which has been used as a stress indicator in chickens. For immune regulation, the researchers in this study measured plasma concentrations of cytokines, interleukin-6 (IL-6) and interleukin-10 (IL-10). IL-6 promotes the migration and proliferation of both T and B lymphocytes. Their results showed a higher peripheral IL-6 level in the warm perch sys- tem compared to the regular and no perch systems when hens were exposed to a cold ambient temperature for three weeks. “This signals the contribution of prolonged cold stress to immunosuppression in the regular perch and no perch groups of hens, while the provision of warmed perches cush- ions the negative effects of a low ambient temperature”, they concluded.


Perches for different growth phases It was concluded that provision of constantly warmed perch- es assists laying hens with thermoregulation during exposure to the cold, as indicated by the measured outcomes of feed consumption, body weight loss, rectal temperature, foot sur- face temperature, egg quality traits, thyroid hormones and immunoregulation. The researchers commented that: “The re- sults show that the use of a warmed perch system could pro- vide a novel thermal device to help reduce cold stress during the winter season without compromising air quality in the poultry house. Considering the variation in plumage cover observed in laying hens with age, this study also provides in- sights for examining the effects of a warm perch system on the different growth phases of laying hens under various cold conditions”.


PHOTO: KOOS GROENEWOLD


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