Heritability of body surface temperature in hens estimated by infrared thermography at normal or hot temperatures and genetic correlations with egg and feather quality.
Exposure of laying hens to chronic heat stress results in loss of egg production. It should be possible to improve hen resilience to chronic heat stress by genetic selection but measuring their sensitivity through internal temperature is time consuming and is not very precise. In this study we used infrared thermography to measure the hen's capacity to dissipate heat, in a commercial line of laying hens subjected to cycles of neutral (N, 19.6°C) or high (H, 28.4°C) ambient temperatures. Mean body temperatures (BT) were estimated from 9355 infrared images of wing, comb and shank taken from 1200 hens. Genetic parameters were estimated separately for N and H temperatures. Correlations between BT and plumage condition were also investigated. Wing temperature had low heritability (0.00 to 0.09), consistent with the fact that wing temperature mainly reflects the environmental temperature and is not a zone of heat dissipation. The heritability of comb temperature was higher, from 0.15 to 0.19 in N and H conditions, respectively. Finally, the shank temperature provided the highest heritability estimates, with values of 0.20 to 0.22 in H and N conditions, respectively. Taken together, these results show that heat dissipation is partly under genetic control. Interestingly, the genetic correlation between plumage condition and shank and comb temperatures indicated that birds with poor condition plumage also had the possibility to dissipate heat through featherless areas. Genetic correlations of temperature measurements with egg quality showed that temperatures were correlated with egg width and weight, yolk brightness and yellowness and Haugh units only under H conditions. In contrast, shell colour was correlated with leg temperature only at thermo-neutrality.
1UR83 Recherches Avicoles,INRA Centre Val de Loire,37380 Nouzilly,France.
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Loyau
2GABI,INRA,AgroParisTech,Université Paris-Saclay,78350 Jouy-en-Josas,France.
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Zerjal
3WUR Animal Breeding and Genomics Centre,P.O. Box 338,6700 AH,Wageningen,the Netherlands.
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Rodenburg
5ISA,1 Rue Jean Rostand,BP 23,22440 Zoopôle,Ploufragan,France.
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Fablet
2GABI,INRA,AgroParisTech,Université Paris-Saclay,78350 Jouy-en-Josas,France.
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Tixier-Boichard
3WUR Animal Breeding and Genomics Centre,P.O. Box 338,6700 AH,Wageningen,the Netherlands.
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Pinard-van der Laan
1UR83 Recherches Avicoles,INRA Centre Val de Loire,37380 Nouzilly,France.
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Mignon-Grasteau
D000818:Animals; D001831:Body Temperature / Q000235:genetics* / Q000502:physiology; D001833:Body Temperature Regulation / Q000235:genetics / Q000502:physiology; D002645:Chickens / Q000235:genetics*; D004531:Eggs / Q000592:standards*; D005241:Feathers / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D007259:Infrared Rays; D010058:Oviposition / Q000502:physiology; D010063:Ovum / Q000166:cytology; D013817:Thermography; D014921:Wings, Animal / Q000502:physiology
adaptation; egg quality; genotype–environment interaction; heat stress; laying hens