Dietary chromium-methionine supplementation and broiler (22–43 days) responses during heat stress. 2 - Physiological variables, and heat shock protein 70 and insulin-like growth factor-1 gene expression

Abstract

Context

Dietary supplementation with trace mineral chromium (Cr) has been shown to enhance the physiological responses of broilers subjected to heat stress (HS), modulate gene expression, and improve performance.

Aims

This study aimed to evaluate the impact of chromium–methionine (CrMet) supplementation on growth performance, body temperatures, lymphoid organ weights, hormones, blood parameters, and the expression of heat-shock protein-70 (HSP-70) and insulin-like growth factor-1 (IGF-1) genes in broilers under HS conditions (33°C for 12 h/day).

Methods

In the first experiment, 336 22-day-old male broilers were randomly distributed into four blocks with six treatments (0, 0.10, 0.20, 0.40, 0.80, and 1.20 mg/kg CrMet) and eight replicates with seven birds per cage. These broilers were subjected to HS from 22 to 43 days of age. In the second experiment, 24 male broilers, in total, at 43 days of age, previously exposed to HS, were randomly distributed to the same six treatments from the first experiment, with four replicates. Breast samples were collected for the analysis of HSP-70 and IGF-1 expression.

Results

A quadratic effect (P < 0.05) was observed on bodyweight gain (BWG) and feed conversion ratio (FCR). The supplementation of 0.71 and 0.68 mg/kg improved BWG and FCR, respectively. At 28 days of age, cloacal and mean body temperatures, corticosterone, and thyroid hormones were quadratically affected (P < 0.05), while at 43 days of age, a linear effect (P < 0.05) was observed on haemoglobin concentration. There was a reduction (P < 0.05) in the expression of HSP-70 and an increase in IGF-1 (P < 0.05) in the breast tissue of broilers supplemented with CrMet.

Conclusions

The supplementation with 0.71 mg/kg and 0.68 mg/kg of CrMet improved BWG and FCR, respectively. Additionally, the supplementation with 0.80 mg/kg improved hormones, reduced HSP-70 and increased the expression of IGF-1 in broilers during HS.

Implications

These findings suggest that CrMet can be included in the diet of broiler chickens subjected to HS to enhance physiological responses and performance.