I recently had the opportunity to spend several days alongside a senior veterinary student who was participating in a two-week rotation with our practice. Our focus those days was primarily nursery and grow-finish health, and we were able to visit a variety of sites. During the drive home on Friday afternoon, we attempted to wrap up our week, discussing all of the things we’d seen. When the student commented, “I think we talked about lameness, arthritis or stiff pigs within every barn we were in this week,” the conversation quickly evolved, and we spent a majority of our trip on this very challenging subject.
Although differences exist as to the cause, age affected and severity, we do see an increased frequency of leg and joint disorders in growing pigs. We know the primary causes: infectious, nutritional and/or physical (examples being poor anatomical structure or rapid growth). We know the effect: reduced performance, increased mortality and possibly an impact on the animal’s well-being. We don’t always know how to prevent the occurrence of this problem.
A producer, who cares for two wean-to-finish barns and is contracted to purchase weaned pigs every six months, changed sources when the contracted farm became infected with porcine epidemic diarrhea virus (PEDV) last winter. Pigs had done well through the nursery and early finish stage, but now at approximately 240 lb. there are an increasing number of pigs that really struggle to rise during morning and afternoon chores. The producer commented that the worst pigs were no longer able to get up and required euthanasia. Each site houses 2,400 head with small pens of 25-30 pigs. Walking through, observers noted that three to five pigs in each pen would drag themselves on front legs before attempting to rise. Others in the same pen appeared clinically normal. Of those that had difficulty getting up, a couple per pen actually required physical assistance to rise. Stepping back out into the alleyway to watch, observers saw that most of the stiff pigs had appetites. They tended to shift weight on rear legs until becoming comfortable; then most would finally bear weight on all limbs. Pigs had muscle tone and normal foot positioning, indicating less likelihood of a neurologic disorder. Those most severely affected had a tucked-in appearance, suggesting they weren’t rising often enough each day to fulfill their appetite.
Because this was a new source of lameness with an unknown cause, and there was still time remaining to treat the group before marketing began, it was decided to euthanize two pigs for a diagnostic investigation. Both pigs chosen were showing previously described signs. On post-mortem, no overt lesions to lungs, heart, intestines or colon were identified. One pig did have moderate gastric ulceration. Ribs were difficult to break and were submitted.
Postmortem of joints was more revealing, with both the knee and elbow joints containing a large volume of a reddish-brown fluid. Articular cartilage was intact, and no other lesions were identified. Both a front and rear limb were submitted, along with spinal cord.
Mycoplasma hyosynoviae, a bacterial agent that slowly builds within joints leading to arthritis, was identified from samples. No other significant diagnostic findings were made. An antibiotic program for the group was initiated. Because these pigs had been arthritic for several weeks, treatment wasn’t able to completely eliminate symptoms, but the producer did describe some measurable improvement.
A farrow-to-finish producer had a group of 60-lb. pigs experiencing a rapid onset of severe lameness, generalized weakness and multiple leg breaks during the move from nursery to finisher. The group started without incident after weaning, and up to two weeks ago had been performing well, with good feed intake and minimal mortality. Pigs on initial visit showed neither respiratory signs nor diarrhea. Pigs did vocalize when moved or attempting to rise. Three pigs with fractured limbs were euthanized. All pigs had similar pathology, including minor pneumonia and long bones that seemed softened or brittle. Tissue samples, including ribs and femur, were collected. Serum was also drawn from multiple live pigs. Luckily, feed samples were retained, and these were also sent to a laboratory for vitamin and mineral analysis.
No viral or bacterial pathogens were detected. Micro-scopic investigation showed no changes related to an infectious agent. Mineral content of bone was well below established normal values. Serum taken from affected pigs was low in calcium. Feed analysis showed adequate dietary calcium, but vitamin D was absent. These pigs had been consuming calcium but were unable to absorb a majority of this due to insufficient vitamin D. Supplemental vitamin D was immediately provided to the affected group, and all other diets provided by the feed mill were immediately fortified.
Arthritis, stiffness and generalized lameness all have an impact on growing pigs. Unfortunately, some of the processes that lead to these conditions are slow to develop. Pigs are also good at masking mobility disorders. With this combination, it can be really difficult to address by the time clinical signs are recognized. Complete diagnostic submissions, including joints and bone as well as feed samples, are helpful in diagnosis and help guide the preventative measures that can be taken to reduce future frustrations.