How long to keep a calf in a dark barn?

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Jul 27, 2022
Washington State
Is it necessary to leave a steer in a dark barn all day? I was thinking maybe putting them in the dark around 4:00 PM just like when it gets dark in winter time so they have that nice winter coat all year long. Or do they need to be in the dark all day to have nice hair? They will still be under fans all day but in not sure how healthy it is for them to be in the dark 24/7