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This paper reviewed the effects of lighted incubation (in ovo lighting) on incubation performance and chick quality in broilers. Globally, the broiler chicken industry is among the fastest growing commercial sectors. Chicken meat has the fastest growth rate compared to other common animal protein sources, and its demand will always increase due to increasing population growth worldwide. Therefore, a need for a proportional increase in hatchery efficacy is also increasing with this demand. Over the past decades, implementation of artificial light during incubation in broiler chickens has accelerated with key considerations such as light colour, light source, photoperiod, eggshell colour, pigmentation, light shape and light intensity. Photostimulation has a significant effect on embryo development during the last quarter (from 14 to 21 day of incubation). However, incubating eggs under light from day 1 to 18 improves embryo development and hatchability compared with lighting for 21 days. A photoperiod of 12 L:12 D improves hatchability, chick weight and leg health compared with 24 L and 24 D. High light intensity decreases hatching traits such as chick weight. While incubation under green light increases muscle growth and weight gain of chicks, lighted incubation with red and white light enhances hatchability compared with other wavelengths and darkness. In conclusion, it is important to continue studies on lighted incubation to identify the exact mechanisms of how other light colours impact embryogenesis and investigate the interaction or synergistic effects of a combination of two or more wavelengths.

In skeletal muscle, transforming growth factor-β (TGF-β) family growth factors, TGF-β1 and myostatin, are involved in atrophy and muscle wasting disorders. Simultaneous interference with their signalling pathways may improve muscle function; however, little is known about their individual and combined receptor signalling. Here, we show that inhibition of TGF-β signalling by simultaneous muscle-specific knockout of TGF-β type I receptors Tgfbr1 and Acvr1b in mice, induces substantial hypertrophy, while such effect does not occur by single receptor knockout. Hypertrophy is induced by increased phosphorylation of Akt and p70S6K and reduced E3 ligases expression, while myonuclear number remains unaltered. Combined knockout of both TGF-β type I receptors increases the number of satellite cells, macrophages and improves regeneration post cardiotoxin-induced injury by stimulating myogenic differentiation. Extra cellular matrix gene expression is exclusively elevated in muscle with combined receptor knockout. Tgfbr1 and Acvr1b are synergistically involved in regulation of myofibre size, regeneration, and collagen deposition.