Because antibiotics fed to nursery pigs have helped control the Lawsonia intracellularis bacterium that causes ileitis, the clinical signs — diarrhoea, gauntness, poor performance — tend to be delayed.

“With the trend toward fewer and fewer [feed] antibiotics, we expect ileitis to become a more common disease in the mid- to late-nursery period,” Nate Winkelman, DVM, president of Swine Services Unlimited, told Pig Health Today.

He estimates that more than 95% of pig production sites in North America have either clinical or subclinical ileitis.

Reduced nutrient absorption

Lawsonia causes the pig’s intestinal lining to thicken, which reduces its ability to absorb nutrients and negatively impacts feed efficiency and growth performance.

Antibiotics have long been the first choice for managing this enteric disease, but there’s also demand for pigs raised without antibiotics. The challenge, Winkelman said, is meeting that need while still guarding against this costly gut disease.

“You can’t replace antibiotics,” he added. “We’re just looking for other alternatives that might improve performance of infected pigs.”

While there are two ileitis vaccines available — one oral, one injectable — Winkelman said “it takes 4 weeks to maximise immunity” in vaccinated pigs and therefore “the timing isn’t right to protect the nursery pig.”

Looking for possible solutions, he teamed up with Fernando Leite, DVM, who at the time was a graduate research assistant at the University of Minnesota, to study different forms of supplemental zinc in pig diets and its impact on Lawsonia.

It’s well known that zinc plays a role in maintaining intestinal health — in both pigs and people.

“We know that zinc oxide, for instance, can have bactericidal activities, but we wanted to look at an organic form of zinc that can be absorbed differently by the animal,” Leite said. “The trial wasn’t aimed at killing Lawsonia but, rather, helping the pig respond to infection.”

The study revealed that pigs fed the zinc amino acid complex had less severe intestinal lesions associated with Lawsonia and the negative performance impact of ileitis. Both veterinarians find the results promising but emphasise the need to replicate the study to ensure consistent results.

Hyper-immunised chicken eggs

In an earlier study, Winkelman evaluated the use of chicken eggs hyper-immunised with the Lawsonia intracellularis antigen, which were then spray dried and added to swine diets, providing a passive antibody to an ileitis disease challenge.

“We had a 25% improvement in average daily gain and a 26% improvement in average daily feed intake,” Winkelman noted.

So, while the search for antibiotic alternatives continues, there’s growing evidence that these alternatives have potential.

“We’re looking at feed, water, vaccine options — all kinds of things that we need to do to replace antibiotics,” where needed, he added.

“As veterinarians, we have to be careful when we remove antibiotics, because there’s an impact on performance, mortality and morbidity from an animal-welfare standpoint,” Winkelman said.

“But if the consumer is willing to pay for…no-antibiotics-ever pork and there’s a market for those pigs, then we need to have alternatives.”