LAUSR

Abstract This study investigated the effect of a novel phosphorylated tocopherol mixture (TPM) on the growth performance, nutrient digestibility, meat quality, and blood plasma markers of inflammation in broilers reared in normal temperatures (NT) or cyclical high temperatures (CHT). TPM has previously been shown to increase the oral bioavailability of lipid soluble nutrients. Following a preliminary dose optimisation study, three hundred and sixty Ross 308 day old broilers were housed in groups of 5 in cages ( n  = 12). Treatments were arranged in a factorial design encompassing 3 dietary TPM levels and ± CHT. From day of placement until d 35, broilers were assigned to 1 of 3 vitamin E-adequate, wheat and soybean meal-based diets containing TPM at 0 (Control), 10 or 20 mg/kg diet. From 21-35 d of age, birds were exposed to either normal temperatures (NT; 22 ± 1 °C; 60% RH) or cyclical high temperature (CHT; 32 ± 1 °C; 8 h; 80–90% RH and 16 h at 22 ± 1 °C; 60% RH). Implementing CHT negatively impacted feed intake (FI), body weight (BW) gain, feed conversion ratio (FCR) and final BW (d 35), apparent ileal digestibility (AID) and shear force of cooked breast muscle. Under both NT and CHT regimes, the TPM 10 group had improved BW gain (d 0-35), FCR (d 0-21) and final BW (d 35) when compared with Control diet groups containing TPM at 0. There was an interaction between diet and temperature regime on AID. The TPM 20 + CHT group had decreased AID of nitrogen (N) and gross energy (GE) when compared with the TPM 20 + NT group. However, there was no effect of the Control or TPM 10 on AID under either temperature regime. Breast muscle from CHT birds had increased temperature and shear force when cooked, and decreased pH and drip loss when compared with NT birds. The TPM 10 group tended to have lower drip loss (P = 0.057) under both temperature regimes when compared with the Control group. Implementing CHT increased the plasma concentration of select cytokines and chemokines (INFγ, IL-6, IL-10, IL-16, IL-21 and CCL5) when compared with the NT treatment. Birds offered the TPM 10 diets had numerically lower concentrations of all plasma chemokines and cytokines when compared with the Control diets. In summary, CHT depressed performance and nutrient digestibility and negatively impacted breast muscle quality. The TPM 10 treatment improved growth performance variables under both NT and CHT regimes and tended to reduce muscle drip loss.