Two accepted facts stand out when pig health discussions come round to respiratory disease in the nursery. First, respiratory disease is the Number-One cause of nursery mortality. Second, a pig that is healthier and heavier leaving the nursery is likely to be also healthier all through grow-finish so it shows a better growth rate to market weight.

While these facts are understood within the pig industry, the timing of treatment for respiratory disease is still an oft-debated topic. When to treat? Producers and veterinarians alike look for answers to this question. It is complex and may have multiple solutions.

In many cases, action plans are implemented too late to capture the full value that would have been achieved by earlier intervention. The impact of a fairly new approach to treating respiratory disease early has been examined in a new study, results for which were presented at the 2008 annual meeting of the American Association of Swine Veterinarians.

Conducted by Dr Karen Lehe of Round Grove Veterinary Services in Indiana, USA, the study looked at treating pigs in the nursery as well as at the sow herd. Its results offer some supporting evidence to veterinary practitioners who believe that you can expect sustainable benefits from early treatment.

The work was done at a commercial farm in Illinois, USA, which had 'significant' respiratory challenges — involving among others the pathogens Pasteurella multocida, Actinobacillus pleuropneumoniae, circovirus and PRRS virus. To reduce the pathogen impact of respiratory disease in the sow herd, tilmicosin was utilised in the lactation diet. The treatment in this phase of production involved sows with nearly 3000 progeny, tracked through from weaning to market for both health observations and performance metrics.

One of the many objectives for Dr Lehe was to determine which respiratory pathogens were being carried from the sow herd to the nursery and whether this transfer could be minimised. The accompanying charts illustrate some key findings of benefits due to improved sow respiratory health. Pigs weaned from sows fed tilmicosin in lactation were 0.27kg heavier at weaning than others in the control group. Mortality rate in the nursery was better for pigs weaned from the treatment group of sows (1.7%) than those in the non-treatment group (2.8%).

Previous papers such as one of the 2006 International Pig Veterinary Society Congress have shown intervention in sows with a confirmed respiratory disease challenge as being able to improve health and performance in the nursery. While confirming the value of early intervention in the sow and in the nursery, Karen Lehe's study also has found significant results from using 200ppm of tilmicosin, a lower dosage than reported in the IPVS paper of 2 years ago.

Unlike grower and finisher pigs that are coughing and visibly dying from respiratory disease, sows do not necessarily have the same clinical signs. It is rare to find an overwhelming amount of respiratory disease as a primary cause of death or culling in the sow herd, Dr Lehe says. Most respiratory diseases originate in the piglet. But they can still pose a threat to the sow's health and production.

The threat continues through the production process because a respiratory challenge affecting the sow herd can be expected to show up in the pig flow as well. Dr Doug Powers runs Swine Veterinary Care and Consultation in Indiana, USA. He says that the effects of respiratory issues in sows transfer to their pigs in the form of greater pre-weaning mortality, lower average daily weight gain and poorer feed efficiency.

Dr Lehe notes that other factors for sows, such as reproductive failure and lameness, typically grab more attention. "So people are wondering whether a respiratory product is going to help them in the breeding herd. I cannot answer that for sure, but I do know that sows consistently have improved weaning results and reduced wean-to-service interval when they exit the barn" after early intervention. "That tells me there is strong evidence we are improving the health of the sow during the lactation period."

Because the sow often appears healthy, even when she is not, some producers resist the notion of intervention until reproduction results are affected. That is a potentially profit-robbing decision, Dr Lehe warns. "You are probably passing pathogens from the sow to the pig and they develop into the problems we have to deal with later in larger respiratory outbreaks in the flow," she says.

Even then there is the obvious question: Can you actually intervene in the sow diet and expect to have this effect on pigs throughout the nursery and finishing phases of production? "The answer is yes," she says. "We are seeing repeated results that show intervening in the sow diet has a very positive effect in the flow."

Even nursery pigs sometimes deceive. Maybe a healthy-looking pig at weaning has pneumonia already, Dr Lehe remarks. Sow herds with respiratory disease challenges have reduced performance and can transfer those detrimental pathogens to their weaned offspring, resulting in reduced nursery performance.

Lung lesions

The IPVS study in 2006 had been surprising because when it evaluated healthy-looking pigs at weaning, it found significant lung lesions indicating pneumonia. Veterinarians see a lot of healthy pigs at weaning and often do not expect that disease is already brewing beneath the surface, she comments. That study by Dr Glen Almond and colleagues at North Carolina State University, USA, reported finding gross pneumonia lesions in 23.2% of the control pigs, but only in 6.9% of pigs weaned from sows that had been treated for respiratory disease. Dr Almond's study also documented several other improvements, such as that overall attrition losses (a combination of pre-weaning mortality, nursery mortality and culling rate) were 22.6% lower in the pigs from treated sows. Moreover, the weight of pigs leaving the nursery was 19.9% higher for the sow group treated during lactation and these sows receiving treatment for respiratory disease produced 9.3% more pigs into the finisher pens than from control sows.

Dr Lehe advises identifying sick pigs earlier in the nursery. Too often, she says, a producer waits until an animal clearly needs treatment and then reaches for the least-cost injectable. Taking a closer look at individual animals — and possibly intervening when the pig first becomes sick — is a better course of action, even though it requires having people in the barns who are adequately trained to catch disease early. Additionally, the fact that producers wean groups of pigs and not single animals means recognition of the first sign of illness and timely intervention have the chance to stop any nursery respiratory infection transferring from animal to animal.

According to Dr Lehe, herd operators need to look beyond the cost of treating a sow in lactation and also take account of the return on investment. Quite simply, treatment should mean more weight moved out of the nursery and more pork marketed. When Dr Doug Powers in Indiana also looked at respiratory treatment from an economic standpoint, in one situation he found a return on investment of US$3.50 per litter based on the improved pre-weaning mortality alone.

Dr Lehe agrees that respiratory treatment should not be a hasty decision. It needs to be based on a good diagnosis and the correct recommendations for intervention. Also, the costs and application of the treatment must be balanced against the value of reduced attrition or improved quality of the pigs moved to finishing.PIGI