Impact of dietary magnesium supplementation from different sources on meat quality of broilers under heat stress

The increase of ambient temperature due to global warming has led to heat stress (HS) in livestock exploitations, particularly affecting broiler production. This work was designed to evaluate the effect of Mg supplementation on mineral absorption and meat quality in broilers under HS by using sulphate (MgSO4, anhydrous) or oxide (MgO) as Mg sources. These sources were previously selected by in vitro digestion and intestinal cell culture absorption assays. For the in vivo trial, Cobb500 broiler chickens were maintained for 28 days under different ambient temperature conditions: thermoneutral (TN, 23-25 °C) or HS (27-33 °C). Mg supplementation did not affect ileal Mg digestibility but impaired those of Ca and P (P<0.05), which may be linked to impaired phytase activity. The damaging effect of HS in breast yield was prevented by dietary Mg addition and the sulphate source resulted in cooked meat with more reddish (higher a*) and intense colour (chroma index C*) than that of control or MgO groups. Moreover, supplemental MgSO4 was effective in reducing water losses of breast meat caused by HS, reducing 22% of the cooking losses compared with the control group. Meat texture analysis showed lower shear force values in breast muscle from broilers fed the MgSO4 compared with controls or MgO groups (P = 0.001), indicating less effort required to chew and swallow the meat. In conclusion, Mg in the sulphate form had better availability than the oxide forms here assayed, and its dietary supplementation was more effective to improve meat quality traits in broilers under HS conditions.