I used to be in the DSA for Bangs, We had to have older cattle bleed before sale. There was sale barns in the area and the State covered the cross for drawing the blood. We bleed the whole herd when we preg checked, it gave us a 30 day window for sales. The vet bleed then preg the cow . Usually pretty fast sometimes there be trouble finding a vein. and there was the occasional of getting blood from a neck artery. This was a vet that took thousands of samples every year.