Effects of dietary supplemental chromium methionine, zinc oxide, and ascorbic acid on performance, egg quality traits, and blood parameters of laying hens subjected to heat stress

Based on a 2x2x2 factorial, the effects of three dietary supplemental including chromium methionine (Cr) (0 and 400g/kg diet), zinc oxide (Zn) (0 and 30mg/kg diet), and vitamin C (VitC) (0 and 250mg/kg diet) on egg production (EP) and mass (EM) and egg traits in heat-stressed (HS) Lohmann LSL-Lite laying hens from 30 to 45 weeks of age were evaluated. The house temperature was kept at 18 degrees C (weeks 30-40 of age) and then increased to 32 degrees C (weeks 41-45 of age). Dietary treatments had no significant effects on EP, egg weight, EM, and feed conversation ratio before and after exposure to heat stress (P>0.05). Decreased feed intake intake was observed in group of VitC during exposing to HS (P<0.05). Dietary supplemental Cr decreased serum glucose concentration before HS (P<0.05). A combination of Cr and VitC increased serum glucose concentration before and during HS (P<0.05). Decreased serum concentration of Zn was detected in hens fed the diets with VitC, Cr, or Zn (P<0.05). Increased serum concentration of Cr was observed in hens fed the diets supplemented with Cr (P<0.05).