Effects of In Ovo Methionine-Cysteine Injection on Embryonic Development, Antioxidant Status, IGF-I and TLR4 Gene Expression, and Jejunum Histomorphometry in Newly Hatched Broiler Chicks Exposed to Heat Stress during Incubation

In the current study, we hypothesize that the In ovo concurrent injection of methionine (Met) and cysteine (Cys) may have positive effects on embryonic development, insulin-like growth factor-I (IGF-I) and toll-like receptor-4 (TLR4) gene expression, antioxidant status, biochemical profile, and jejunum histomorphometry of newly hatched broiler chicks exposed to heat stress during the incubation period. As indicated, the In ovo injection of Met and Cys resulted in increased hatch weight, higher levels of total antioxidant capacity, and glutathione activity in the serum and tissues. At the same time, a decrease in the level of heat shock protein-90 and an increase in TLR4 and IGF-I expression in the tissues was observed. In addition, the In ovo injection of Met and Cys improved jejunum histomorphometric parameters of newly hatched broiler chicks. Generally, the concurrent In ovo injection of Met and Cys improved broiler embryonic development, antioxidant status, TLR4, and IGF-I expression and jejunum histomorphometric parameters in newly hatched broiler chicks exposed to heat stress conditions during incubation