I access the cephalic vein for weekly blood collection (approx 15 mL) using a SurFlash 18G catheter. For restraint the sheep are lifted across a bench. With their feet off the ground they sit still during the blood collection and other interrogative procedures. We use at least 2 people (to lift the animal).

Thanks Rafael Ramirez, please post one or two picture of collecting blood from sheep of your method

Sure. Here are some pictures.

Materials include: SurFlash I.V. Catheter (18G x 1.25", green cap), I.V. connector tube (top), Vacutainer Blood Collection Tube (orange cap with SST for serum collection), a needle (with rubber cover) is already positioned in the transparent green safety sheath in this photo.

Here's the initial vein puncture using the SurFlash IV Catheter and with a rubber tube temporarily tying off the leg proximal to the puncture.