title: Genetic variations alter production and behavioral responses following heat stress in 2 strains of laying hens.
abstract: Genetic differences alter the type and degree of hens' responses and their ability to adapt to a stressor. This study examined the effects of genotypic variations on the productivity and behavior of laying hens following heat stress (HS). Two strains of White Leghorn hens were used: DXL (Dekalb XL), a commercial strain individually selected for egg production and KGB (kind, gentle bird), a strain selected for high group productivity and survivability. Ninety hens (48 DXL and 42 KGB) at 28 wk of age were randomly assigned to either a hot (H: mean = 32.6°C) or control (C: mean = 24.3°C) treatment and housed in pairs by strain for 9 d. Egg production and quality, behavior, body and organ weights, and circulating hormone concentrations were measured. Heat-stressed hens had lower egg production [adjusted (adj) P < 0.001] than their respective controls. Among H-DXL hens, egg weight tended to be reduced at d 1 and was reduced at d 9 (adj P = 0.007), but was reduced only at d 9 among H-KGB hens (adj P = 0.007). Eggshell thickness was also reduced among H hens at d 9 (adj P = 0.007), especially among H-KGB hens (adj P = 0.01). Plasma triiodothyronine concentration was reduced among H-hens (adj P = 0.01), especially among H-DXL hens (adj P = 0.01). Neither temperature nor strain affected the plasma thyroxine and plasma and yolk corticosterone concentrations. Heat-stressed hens spent less time walking (adj P = 0.001) and more time drinking (adj P = 0.007) and resting (adj P = 0.001) than C-hens. The results indicate that although HS reduced production and caused behavioral changes among hens from both strains, the responses differed by genotype. The data provide evidence that genetic selection is a useful strategy for reducing HS response in laying hens. The results provide insights for conducting future studies to develop heat-resistant strains to improve hen well-being, especially under the current commercial conditions.
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Mack
authors.forename: J N
authors.initials: JN
authors.lastname: Felver-Gant
authors.forename: R L
authors.initials: RL
authors.lastname: Dennis
authors.forename: H W
authors.initials: HW
authors.lastname: Cheng
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001835:Body Weight; D002645:Chickens / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D003345:Corticosterone / Q000097:blood; D005247:Feeding Behavior; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D018869:Heat-Shock Response; D007194:India; D009929:Organ Size; D010063:Ovum / Q000254:growth & development / Q000502:physiology; D011863:Radioimmunoassay / Q000662:veterinary; D011897:Random Allocation; D012098:Reproduction; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D013974:Thyroxine; D003345:Corticosterone