Attach the Vacutainer needle on to the needle holder.
Insert the Vacutainer tube into the other end of the needle holder until the stopper touches the back portion of the needle. Do not puncture the stopper. Hold these assembled materials in one hand.
Lift the cow's tail with your free hand.
Insert the needle about 1/2" deep & perpendicular to the tail at the under side, midline & at about 3 to 6" away from the base of the tail. In this region, there is a midline ridge of skin through which the needle can be pushed through.
Once the vein has been punctured, blood will appear at the junction of the stopper & the back portion of the needle. If it does not appear, pull the needle out slightly & carefully re-insert into a different direction until the vein is punctured.
Once blood is seen, push the tube onto the needle. Be sure to keep the needle under the skin. The "vacuum" will pull blood into the tube & if lost, blood cannot be collected. Use a new tube if this happens. Collect a minimum of 2cc of blood. Withdraw the needle from under the skin & detach the tube.
Immediately label the tube with the animal's identification name or number, along with the farm name neatly in permanent marker. Place the tube in an ice rack or refrigerator until it is shipped. Discard each used needle into a "sharps" container. The needle holder is re-usable; however, new needles must be used for each individual's blood draw.