September deer antlers in velvet sometimes are not receptive to chasing the blood out in this manner. Care MUST be taken, too, as forcing any liquid into something using a syringe can result in blowback. Formeldehyde, being a carcinogenic, would not be something Id want coming back onto me. Use goggles and protection. If you are going to go the cheaper route, try getting them into the pickle to preserve them, after flushing out the blood.