Effects of brown seaweed products on growth performance, plasma biochemistry, immune response, and antioxidant capacity of broiler chickens challenged with heat stress

Brown seaweed (Ascophyllum nodosum) is an exceptional bioactive substance known for its excellent antioxidant ability. Given the potential benefits of brown seaweed, the current study was conducted to determine its efficacy on growth performance, blood biochemistry, immunoglobulins (IgG and IgM), and the antioxidant capacity of broiler chickens challenged with heat stress (HS). A total of 336 mixed-sex Ross 308 broiler chicks (one-day-old) were randomly assigned into two groups; The thermoneutral group (TN, broilers were raised at 24 ± 1°C); and the heat stress group (HS; broilers were exposed to 32°C to 34°C, 8 h/d from day 21 to 27; the temperature in the remaining time was same as TN group). All birds in each group were randomly allotted to 4 dietary treatments—Negative control (NC) (without seaweed), NC + 1 mL seaweed extract (SWE) in drinking water, NC + 2 mL SWE in drinking water, and NC + 2% seaweed meal (SWM) in feed. Each treatment was assigned to six replicates with 7 broilers/replicate. Average body weight gain (ABWG), average feed intake (AFI), average water intake (AWI), feed conversion ratio (FCR), and mortality were determined weekly. On day 28, two male birds/cage were euthanized to collect blood and immune organs for subsequent biochemical, antioxidant, and immune status analysis. Data were analyzed as a 4 × 2 factorial analysis of variance using the GLM procedure of Minitab software. Overall, 2% SWM inclusion significantly increased (P < 0.05) the AFI, ABWG, and AWI of broiler chickens irrespective of HS. HS significantly reduced (P < 0.05) AFI and increased (P < 0.05) the bird's rectal temperature, plasma concentrations of sodium, chloride, glucose, amylase, and uric acid compared to TN birds. HS increased (P < 0.05) serum IgM and IgG and decreased plasma glutathione reductase and glutathione peroxidase compared to TN birds, while the activity of superoxide dismutase was not affected by HS and dietary treatments. 1 mL SWE in water and 2% SWM in feed significantly reduced (P < 0.05) the plasma activity of alanine aminotransferase and gamma-glutamyl transferase of heat-stressed broilers, respectively compared to other treatments. Conclusively, dietary supplementation of brown seaweed improved the growth performance of birds irrespective of HS and may help to reduce the negative effects of HS by improving the plasma enzyme activities of heat-stressed birds.