Effects of Nano Emulsified Vegetable Oil and Betaine on Growth Traits and Meat Characteristics of Broiler Chickens Reared under Cyclic Heat Stress

SIMPLE SUMMARY: Thermal stress is a critical issue for poultry during the summertime. It is imperative to overcome this problem by controlling the environment inside poultry houses or by water additives. This experiment evaluated the effects of two supplements for broilers in water. Nano-emulsified vegetable oil or betaine was used in two groups of broilers. One group was kept under a thermo-neutral temperature (24 °C) while the other was kept under a high temperature (35 °C). The high temperature lasted from 21 to 35 days old. The high-temperature group consumed less feed and suffered significantly from lower daily gain. Moreover, the thermo-neutral group had good meat attributes when compared to the high-temperature group. The two supplements improved the ability of broilers to use feed more efficiently and convert it to body gain compared to the un-supplemented birds. In addition, betaine enhanced carcass characteristics such as breast temperature and pH compared to the control. In summary, the heat challenge caused significant disadvantageous impacts on growth efficiency and meat qualities, while the two supplements used herein improved the performance. Therefore, it is recommended to use these supplements in the case of high temperatures inside broiler houses. ABSTRACT: The effects of nano-emulsified vegetable oil (NEVO) and betaine (BET) supplements on growth performance and meat qualities of broilers reared under cyclic heat stress (HS) were investigated. Two hundred and eighty-eight mixed-sex broilers at 21 d were randomly distributed to a 2 × 3 factorial arrangement of treatments formed by two environmental temperatures (thermoneutral (TN; 24 ± 1 °C) and cyclic high-temperature (HT; 35 ± 1 °C)) and three dietary treatments (control (CON), NEVO, and BET). The cumulative performance (21–35 d) revealed a reduction in average daily gain (ADG) (p < 0.05) in the CON compared to NEVO. NEVO and BET groups had a better feed conversion ratio (FCR) and performance efficiency factor (PEF) compared with the CON (p < 0.001, p < 0.01, respectively). The environmental temperature affected daily feed intake (DFI), ADG, FCR, and PEF. The addition of BET improved breast fillets yield, temperature, pH(15min,) and pH(24hr) (p < 0.05) in comparison with the CON. Moreover, the TN group had lower fillet temperature and higher pH(15min) compared to the HT. Moreover, HT increased shear force (SF), hardness, springiness, cohesiveness, and chewiness of the fillets compared to TN. In conclusion, dietary supplementation with BET and NEVO could effectively improve performance parameters and meat characteristics under HS conditions.