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Effects of dietary fat source and embryonic thermal manipulation on muscle yield and meat quality of heat stressed birds

Wall, B., K. Brannan, M. Livingston, K. Livingston and C. Jansen van Rensburg

In the broiler industry, heat stress continues to be an issue that hinders growth performance. Dietary supplemental fats have been shown to aid in the recovery of the birds under heat stress due to high temperatures. Another heat management strategy is the use of thermal manipulation (TM) during incubation. This study sought to investigate alternative dietary supplemental fats and TM during incubation on growth performance and meat quality characteristics, including wooden breast and white strip- ing, in broilers exposed to heat stress during late rearing. All eggs were set in one incubator at 37.6C with a relative humidity (RH) of 56% for the first week. After E7, half of the eggs were incubated at 39.5C with a RH of 65% for 12h a day from E7 to E16. After E16, the eggs were returned to the initial setter at starting temperature until transfer to hatcher at 36.9C with a RH of 54.6%. After hatch, one experimental house was placed with 60 floor pens (18 chicks per pen) and split into a 2×3 factorial design of incubation x diet. Standard commercial starter and grower diets were fed from 0d to 14d and 14d to 28d, respectively. Dietary treatments consisted of poultry fat (4.6%), soy oil (4.6%), and olive oil (4.6%) fed from 28d to 49d. Optimal house temperatures were utilized until 43d, when heat stress was applied for 4h ranging from 34C to 36C. After heat stress, birds remained at optimal temperatures until processing at 49d. Yield cut-outs, cook loss, drip loss, meat color, and myopathy scores were obtained. Data were analyzed as two-way ANOVA using JMP Pro 14. TM resulted in decreased in broiler performance, reduced carcass weight, fat pads, and percent fat pad (P<0.05). Dietary soy oil resulted in reduced drip loss (P<0.05). TM and olive oil resulted in an increase in the b* value of breast muscle (P<0.01). TM resulted in reduced prevalence in muscle myopathies (P<0.05).

To conclude, dietary fat changes did not affect broiler performance or meat yield, however there was an improvement in meat quality characteristics. TM resulted in reduced broiler performance when compared to birds under standard incubation temperatures, and improvements in meat quality characteristics. TM may decrease the prevalence of muscle myopathies due to a decrease in growth performance.