A prevalent problem still plaguing the pork industry is salmonella in the finishing barn. The incidence seemed to increase when furox and other antimicrobial products were removed from the market.
Salmonella is commonly seen as either a scours or respiratory problem - sometimes both. The number of sick animals (morbidity) is usually high, but the mortality will vary with the intensity of the disease, the type of barn, environment, management and the aggressiveness of the treatment.
Case Study No. 1 We were called to a 600-sow, farrow-to-finish unit reporting a respiratory problem in a new finishing barn. The unit was on a weekly farrowing schedule, had nursery space for 8 weeks, finishing space for 16 weeks.
The non-vaccinated sow herd had been through a Porcine Reproductive and Respiratory Syndrome (PRRS) outbreak. Farrowing rate had dropped to about 60% due to abortions and recycles. Pigs weaned from several farrowings did poorly in the nursery. This led to a finishing barn picture that was a little confusing because we were called in 10-12 weeks after the PRRS outbreak.
The four, 300-head finishing rooms each had pigs of different age groups and varied considerably in size. Respiratory problems ranged from slightly increased respiration to severe thumping. There was a high percentage of stunted and gaunt, poor-doing pigs, several with very loose stools. A few pigs had discolored and purple ears. Death loss was well over 4-5%, some rooms running up to 15%.
Lab work confirmed salmonella with a Pasteurella multocida involvement. Lungs showed interstitial pneumonia lesions, characteristic of either a salmonella or PRRS infection. Serology showed most pigs had fairly high ELISA titers to PRRS virus.
We felt the pigs were set back by the presence of PRRS first in the nursery then also in the finisher. When stressed, pigs broke with salmonella as a secondary problem. Because the pigs were doing poorly in the nursery, small groups were backing up in the finisher. To keep production flowing, the producer mixed groups of pigs in the same rooms until group sizes returned to normal levels. The problem snowballed despite his efforts.
Our game plan considered that the PRRS infection in the sow herd and nursery pigs was settling down, but was still present. Groups remained small due to the high abortion rate. We marketed the healthy and lightweight pigs and euthanized those that had no chance of economic recovery. Pigs were regrouped by size, moved to an open-front unit and injected on two consecutive days with a salmonella sensitive antibiotic. Another antibiotic was added to the water. Pigs that responded poorly were injected with a third antibiotic for two more days.
Finishing rooms were completely emptied, disinfected and sat empty for a week. Until group sizes no longer allowed, we put two weeks worth of pigs in each room. Once production levels returned to normal, we placed one group per room. Rooms were kept all-in, all-out, to continue breaking the disease cycle.
Pigs were kept on Mecadox as long as legally possible in the nursery and finisher. We also pulse-medicated the nursery twice and the finisher once. The PRRS is now under control. Salmonella has not rebroken in the finisher barns. We discontinued pulse-medication in the finisher, but continue the practice at 120-150 lb.
The key for this producer was to break the cycle right away, cut his losses, institute long-term management strategies rather than try to vaccinate and medicate through the problem.
Case Study No. 2 The second case involved a producer who switched from a farrow-to-finish operation to a feeder-finisher. He purchased pigs from two sources and placed them in a two-room, 1,000 head finishing barn.
About 30% of pigs in one room showed signs of scours; another 25% showed a wide range of respiratory distress.
A laboratory diagnostic workup yielded positive cultures for salmonella in the lungs and intestinal tracts. The histology showed interstitial pneumonia, a common lesion in salmonella or PRRS cases.
The pigs were treated with samonella sensitive antibiotics in the water for five days and by injection for two days. The pigs responded but death loss still reached 4% in that room. Another 2-3% were stunted.
Although the other room had not broken or shown any clinical signs, we vaccinated those pigs for salmonella as a preventative measure, using two doses of a modified live salmonella vaccine. As the vaccine protocol would allow, we also used a water pulse-medication treatment to prevent pigs from becoming infected with salmonella. There was some concern there might be antibiotic interference with the vaccination response since a modified live vaccine was used. The producer took greater care to always walk this room first and wear different coveralls and boots when checking the other rooms. This group made it to market without signs of salmonella.
The barn was emptied, cleaned and disinfected completely before new, single-source pigs were introduced. It took two weeks to stock the barn. The new groups finished without any samonella outbreaks.