Tri-State Swine Nutrition Guide

Bulletin 869-98

Antibiotics and Antimicrobial Agents

These compounds, when added to swine diets at low dietary levels, have been shown to improve animal growth, feed conversion, and reproductive performance. At high (therapeutic) concentrations, these agents are used to cure or prevent specific diseases or disease conditions. For either situation, they should only be used at the dietary concentration and/or only in combinations approved by FDA.

Nursery pigs almost always exhibit a beneficial response to dietary antibiotic inclusion, resulting in improved gains and feed conversions within a range of 5 to 15%. The response is generally higher (10 to 15%) when pigs are housed on solid floors and bedding. With pigs that are reared in raised decks or under more sanitary conditions, the performance benefits are somewhat lower (6 to 10%). Growing pigs (40 to 150 lbs.) also exhibit a growth response to antibiotics (4 to 6%), but the response declines (0 to 4%) as the pig reaches market weight.

Pigs, which are in a very high-health status and/or are placed in new freshly cleaned facilities with excellent management practices, generally respond less to antibiotic inclusion, particularly after they become adjusted to new facilities.

There are two main points of concern when antibiotics are fed to livestock:

• Withdrawal time, if any, must be adhered to because of the potential antibiotic residue that may remain in the animal's tissues.

• Microorganisms sometimes develop resistance to antibiotics, making the antibiotic less effective over time.

Although bacterial resistance can develop to some antibiotics, use of dietary antibiotics continues to be effective in enhancing pig growth and feed-conversion responses. The best advice is to use the antimicrobial products sparingly and in accordance with FDA regulations.

To ensure that pork producers use antibiotics correctly in their swine herds, the National Pork Producers Council has established a Pork Quality Assurance (PQA) program on residue avoidance. This program effectively acquaints producers with different drugs, their level of inclusion, approved combinations, and proper withdrawal times. The FDA's Compliance Policy Guide (CPG 7125.37, Proper Drug Use and Residue Avoidance by Nonveterinarians) outlines the producer's responsibilities when using animal health-care products. The producer must:

• Identify and track animals to which drugs were administered.

• Maintain medication and treatment records identifying: the animals treated; the date(s) of treatment; the drug(s) administered; who administered the drug(s); the amount administered; the withdrawal time prior to slaughter.

• Store, label, and account for all drug products and medicated feeds properly.

• Use only veterinary prescription drugs obtained through a licensed veterinarian based on a valid veterinarian/client/patient relationship.

• Educate all employees and family members involved in treating, hauling, and selling the animals on proper administration techniques; observe withdrawal times; and observe methods to avoid the marketing of adulterated products for human food.

Regulations for distributing new feed medications have recently changed, and details of the regulations are still being developed. The Veterinary Feed Directive (VFD) category of feed, established by Congress as part of the Animal Drug Availability Act (1996), provides a method of distributing new therapeutic drugs in a manner that assures veterinary supervision without making them prescription products. Swine producers should become aware of the new regulations through their feed suppliers, veterinarians, and State Extension specialists.