Correctly diagnosing the trouble and matching the right additive are important. In some cases, you might need veterinary consultation. An example would be in selecting a wormer that has been proven effective against the species of internal parasites your herd has. When the proper anthelmintic is used according to directions, you can expect good results. Wormers designed for roundworms, for example, may have limited effect on a whipworm infestation.
Antibiotics are one of the most common feed additives.
An abundance of research work indicates the effectiveness of antibiotic additives in improving gains and feed efficiency of swine. With normal hogs, the biggest effect of antibiotics is increased daily gain. There is less effect on feed efficiency. Greatest response usually occurs during the early growth period. Pigs that are doing poorly generally are more responsive to antibiotic feeding than thrifty pigs.