sealPurdue News

October 1994

Vaccines, antibiotics might be overkill to rear healthy pigs: study

WEST LAFAYETTE, Ind. -- Separating pigs from their mothers before 21 days is more effective in keeping the offspring healthy than giving vaccines to the pregnant sows or heavily medicating the piglets, a Purdue University study concludes.

Dr. L. Kirk Clark and nine colleagues studied 60 dams and 220 of their offspring, which were divided into three treatment groups. All the pregnant sows were given routine vaccinations for common reproductive infections. Ten also were given antibiotic-supplemented feed, and 20 received extra vaccinations against gastrointestinal and respiratory disorders.

The piglets were given injections of antibiotics for respiratory diseases, or oral antibiotics in their drinking water, or not treated at all. Piglets in each of the treatment groups were separated from their mothers at seven days, 14 days and 21 days. Nasal swabs, blood tests and other tests were performed on the pigs three days after the treatments and 10 days after separation from the sows.

Clark says the study is the first to separate the effects of vaccinating pregnant sows for disease prevention or treating the piglets before weaning from the effects of early weaning on subsequent health of the pigs. Results of the study were published in the May/June issue of Swine Health and Production, the official journal of the American Association of Swine Practitioners.

"Whatever diseases the piglets get, they mainly get from the sow sometime after birth," says Clark, professor of swine herd health in Purdue's School of Veterinary Medicine. "So it makes sense to wean the pigs and separate them from the mothers as early as possible, within limits of affecting the sow's next reproductive cycle."

Pigs are born essentially disease-free, Clark says. In the first week of life, pigs in all of the treatment groups had streptococcus suis, a common type of strep infection on their tonsils. "Basically, the pigs will get strep no matter what you give the sow while she's pregnant or what you give the pigs right after they're born," he says. However, he adds, the presence of strep on the tonsils does not mean that pigs will develop signs of the disease.

About 50 percent of the pigs in all of the groups had haemophilus parasius, a bacteria, in their nasal passages. This occurred even when the mother had the extra vaccinations or the antibiotic-enhanced feed. However, piglets that received antibiotic treatments before weaning were nearly free of the organism. Haemophilus parasius and strep can develop into severe infections in older pigs.

Clark and the other researchers found that weaning pigs about 14 days after birth is best for the sow and for reducing the incidence of diseases in the piglets. Any sooner than that will interfere with the sow's reproductive cycle, reducing her subsequent fertility.

"We found only the strep and the haemophilus parasius in greater than 50 percent of the pigs separated from their mothers at seven days or 14 days," Clark says. "When weaning after 14 days, the incidence of other, more serious diseases goes up."

Keeping the newborns separate from their mothers requires different buildings spaced far enough apart to keep bacteria from being transmitted through the air or by people, although the exact distance needed isn't known, Clark says. Few farmers and commercial producers use separate buildings, he says. Most producers typically wean pigs at 21 to 28 days, he says.

"This technology of separating the piglets from the sows at an early age works best for larger pork producers," he says, "but it's also something the individual farmer can adopt on a smaller scale."

Clark says the study doesn't mean that pork producers should stop using vaccines and antibiotics altogether.

"But it does show that they should be used only strategically on the sows and the pigs, depending on problems within the herd," he says. "How much vaccine and antibiotics are needed will vary from herd to herd."

Clark estimates that early weaning and segregation could save U.S. farmers and commercial pork producers about $200 million to $500 million a year in vaccinations and antibiotics.

The other Purdue researchers are Drs. Michael A. Hill, William VanAlstine, Gregory Stevenson, Kenneth B. Meyer, Ching C. Wu, Kay Knox and Sharon Albregts, all of the School of Veterinary Medicine. Also cooperating in the study were Dr. Timothy S. Kniffen of Genetic Improvement Services, Burlington, Ind., and Dr. Alan B. Scheidt, of SmithKline Beecham Animal Health, Raleigh, N.C.

The study was funded by Genetic Improvement Services, American Cyanamid and the Indiana Pork Producers Association.

Source: L. Kirk Clark, (765) 494-1209
Writer: Ellen Rantz, (765) 494-2073; Internet,
Purdue News Service: (765) 494-2096; e-mail,

NOTE TO JOURNALISTS: Copies of the journal article and b-roll of Dr. L. Kirk Clark at a swine farm are available from Purdue News Service, (765) 494-2096.

* To the Purdue News and Photos Page