General Use Dewormers. Deworming with one in all many anthelmintics (wormers) approved to be used in cattle is an effective preventive practice. Ivermectin for cattle is an effective medication against the inner worm parasites including lungworms as well as cattle grubs and sucking lice. Deworming should start pre-weaning at regarding 3-4 months old. Will add significant weaning weight (20-40 lbs) compared with non-dewormed calves. If kept as stocker calves, deworm again at weaning. Cattle Dewormers, Cattle Wormers, Ivermectin for Cattle, Cattle Ivomec, Beef Cattle Deworming, Cattle Dewormers Products, Veterinary Cattle Dewormers.