Thermal manipulation of the broilers embryos: expression of muscle markers genes and weights of body and internal organs during embryonic and post-hatch days

Abstract

Background: In broilers chickens, the molecular bases for promoting muscle development and growth requires further investigation. Therefore, the current study aimed to investigate the effects of daily thermal manipulation (TM) during embryonic days (ED) 12 to 18 on body, carcass and internal organ weights as well as on the expression of muscle growth markers genes during late embryogenesis and post-hatch days. 1500 fertile Cobb eggs were divided into five groups. The first group was a control group and incubated at 37.8°C. The other four groups were thermally manipulated (TM) and exposed to 38.5°C (TM₁), 39°C (TM₂), 39.5°C (TM₃) and 40°C (TM₄) daily for 18 h, respectively, with a relative humidity of 56%. Body weights (BW) from ED 12 to 18 and on post-hatch days 1, 2, 3, 4, 5, 6, 7, 14, 21, 28 and 35 were recorded. mRNA expression levels of muscle growth factor genes (IGF-1 and GH) and muscle marker genes (Myogenic Differentiation Antigen; MyoD), Myogenin, Pax7, and PCNA) during ED 12 to 18 and on post-hatch days 1, 3, 5, 7, 14 were analyzed. On post-hatch day 35, the carcass and internal organ weights have been also evaluated.

Results: TM during certain days of embryogenesis (ED 12 to 18) did not affect the BW of broilers during their embryonic lives. However, TM, particularly TM₁ and TM₂, significantly increased BW, carcass and internal weights of hatched chicks near to the marketing age (post-hatch days 28 and 35). Most of TM protocols induced up-regulation of muscle growth factor genes (IGF-1 and GH) and muscle marker genes (MyoD, Myogenin, Pax7, and PCNA) during embryonic life (ED 12 to 18) and on post-hatch days.

Conclusion: Among the various TM conditions, it seems that,TM₁ and TM₂ induced a significant increase in BW, carcass and internal weights of hatched chicks near to the marketing age. This increase in BW induced presumably via up-regulation of muscle growth factor genes and muscle growth markers genes during embryonic life (ED 12 to 18) and on post-hatch days. Both protocols (TM₁ and TM2) can be used in real-world applications of poultry industry for maximum benefit.

Keywords: Broiler; Growth factor; Marker gene; Muscle; Thermal manipulation.

Fig. 1

The effect of thermal manipulation (TM) on embryonic body weight in broiler chicks subjected to different thermal manipulation treatments during embryogenesis) n = 3). Control = 37.8°C for 24 h; TM₁ = Thermal manipulation at 38.5°C for 18 h; TM₂ = Thermal manipulation at 39°C for 18 h; TM₃ = Thermal manipulation at 39.5°Cfor 18 h, TM₄ = Thermal manipulation at 40°C for 18 h. ^a-b Within the same ED, means ± SD with different superscripts differ significantly (P < 0.05)

Fig. 2

The effect of thermal manipulation (TM) during embryogenesis on body weight in post-hatch broiler chicks from day 1 to day 35 (n = 20). Control = 37.8°C for 24 h; TM₁ = Thermal manipulation at 38.5°C for 18 h; TM₂ = Thermal manipulation at 39°C for 18 h; TM₃ = Thermal manipulation at 39.5°Cfor 18 h, TM₄ = Thermal manipulation at 40°C for 18 h. ^a–b Within the same day, means ± SD with different superscripts differ significantly (P < 0.05)