title: Dietary chromium methionine supplementation could alleviate immunosuppressive effects of heat stress in broiler chicks.
abstract: The present study was conducted to investigate the effects of dietary supplementation of chromium methionine (CrMet) on performance, immune responses, and stress status of broiler chicks subjected to heat-stress conditions. A total of 450 day-old Ross 308 broiler chicks were randomly distributed between 5 replicate pens (15 birds each) of 6 experimental treatments according to a 2 × 3 factorial arrangement of treatments including 2 temperature conditions (thermoneutral and heat stress) and 3 supplemental Cr levels (0, 500, and 1,000 μg/kg as CrMet). For induction of heat stress, the house temperature was set at 35 ± 2°C from 15 to 42 d of age. Results showed that the chicks subjected to heat-stress condition had lower (P < 0.01) feed intake, BW gain, and deteriorated (P < 0.05) feed conversion values compared with those kept in the thermoneutral house. Dietary supplementation with CrMet increased (P < 0.01) feed intake and improved (P < 0.01) weight gain and feed efficiency. There were significant Cr level × temperature interactions, so that inclusion of CrMet into the diets was more effective in heat-stressed chicks. Exposure to heat stress suppressed (P < 0.01) cutaneous hypersensivity response to phytohemagglutinin-P injection at 30 d of age, and dietary supplementation of 500 μg Cr/kg induced (P < 0.05) this response, with the greater impacts in heat-stressed chicks, resulting in a significant (P < 0.01) Cr × temperature interaction. Antibody responses against Newcastle and infectious bronchitis disease viruses were diminished (P < 0.01) in heat-stressed chicks. Dietary inclusion of CrMet improved (P < 0.05) antibody responses to different immunostimulants, and this effect was more pronounced in heat-stressed chicks. Exposure to heat stress caused a significant (P < 0.05) decrease in the proportion of helper (CD4+) T lymphocytes and increased cytotoxic (CD8+) T lymphocytes, resulting in a decreased (P < 0.01) CD4+ to CD8+ ratio in peripheral blood circulation. Supplementation of CrMet to heat-stressed chicks modulated (P < 0.01) plasma corticosterone level. The present findings indicate that dietary CrMet supplementation could alleviate heat-stress-induced growth retardation in broiler chicks. Moreover, supplemental CrMet modulated suppressive effects of heat stress on cellular and humoral immune responses.
authors.forename: R
authors.initials: R
authors.lastname: Jahanian
authors.forename: E
authors.initials: E
authors.lastname: Rasouli
mesh_terms: D000818:Animals; D002645:Chickens / Q000502:physiology; D002857:Chromium / Q000008:administration & dosage / Q000494:pharmacology*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D018882:Heat Stress Disorders / Q000097:blood / Q000662:veterinary*; D006358:Hot Temperature / Q000009:adverse effects; D007165:Immunosuppression Therapy / Q000662:veterinary*; D008715:Methionine / Q000008:administration & dosage / Q000494:pharmacology*; D011201:Poultry Diseases / Q000097:blood / Q000517:prevention & control*
chemical_list: D002857:Chromium; D008715:Methionine