Effects of Chromium Supplementation on The Performance and The Blood Level of Thyroid Hormones and Cortisol of Broiler Chickens in Normal Condition and Under Physiological Stress

Although numerous reports support the beneficial effects of supplementing chromium (Cr) on broiler performance under normal and stress conditions, the optimal level has not been determined yet.

This study was conducted to investigate the effects of different levels of supplemental Cr on performance, cortisol, and thyroid hormones of broiler under normal and stress conditions.

A total of four hundred forty-eight broilers were used. Broilers allocated into 2×4 factorial experiment included: stress (normal and stress) and 4 levels of supplemental chromium (0, 1000, 2000, 3000 ppb) since day 18. A completely randomized design with 8 treatments and 4 replicates (14 birds per replicate) was used. Dexamethasone used as a stressor for one week (stress period, STP) then experiment continued to day 46 (recovery period, RCP).

Feeding 1000 and 2000 ppb Cr improved feed conversion ratio (FCR) and increased T4 compared to 0 and 3000 ppb Cr in stressed broilers in STP (P<0.05). Feed intake (FI), body weight (BW) and T3 concentration were higher in broilers fed with 1000 ppb Cr in the diet and reared without stress in STP (P< 0.05). Despite the negative effect of stress on performance in RCP, dexamethasone-stressed broilers had better FCR. Feeding stressed birds with 1000 ppb Cr increased blood cortisol whereas it reduced cortisol in the normal-reared birds.

The Dietary supplementation of 1000 and 2000 ppb Cr reduced deleterious effects of physiological stress. Moreover, 1000 ppb Cr improved FI and BW of broilers under normal condition at first week. Feeding high level of chromium under normal and stress conditions did not improve the performance.